WO2011129235A1 - Frp evaluation method and evaluation device - Google Patents

Frp evaluation method and evaluation device Download PDF

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Publication number
WO2011129235A1
WO2011129235A1 PCT/JP2011/058677 JP2011058677W WO2011129235A1 WO 2011129235 A1 WO2011129235 A1 WO 2011129235A1 JP 2011058677 W JP2011058677 W JP 2011058677W WO 2011129235 A1 WO2011129235 A1 WO 2011129235A1
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Prior art keywords
frp
strength
elastic modulus
compressive strength
temperature
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PCT/JP2011/058677
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French (fr)
Japanese (ja)
Inventor
俊雄 宮武
靖 早坂
直大 蛭田
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株式会社日立製作所
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Publication of WO2011129235A1 publication Critical patent/WO2011129235A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/40—Investigating hardness or rebound hardness
    • G01N3/42—Investigating hardness or rebound hardness by performing impressions under a steady load by indentors, e.g. sphere, pyramid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
    • G01N2203/0075—Strain-stress relations or elastic constants
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0076—Hardness, compressibility or resistance to crushing
    • G01N2203/0078—Hardness, compressibility or resistance to crushing using indentation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/0058—Kind of property studied
    • G01N2203/0096—Fibre-matrix interaction in composites
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/022—Environment of the test
    • G01N2203/0222—Temperature

Definitions

  • the present invention relates to an evaluation method and an evaluation apparatus for FRP used as a structural member of various devices, and more particularly to a method and an apparatus for evaluating the strength of FRP by non-destructive inspection.
  • FRP Fiber Reinforced Plastics
  • a resin with a reinforcing fiber (glass, carbon, etc.) having high strength and elastic modulus. Because of its high specific strength, it is widely used as a structural member for various devices. Since FRP is easy to handle, when manufacturing large structures, sheet-like fibers are laminated in accordance with the mold, and then the resin is applied, or the resin is soaked in the sheet-like fibers. It is often manufactured by the method of stacking on a mold in the state of being.
  • Resins have a temperature at which the characteristic called the glass transition temperature (Tg) changes greatly.
  • Tg glass transition temperature
  • the elastic modulus and strength of the resin rapidly decrease.
  • This temperature varies depending on various factors such as the type of resin, the blending ratio at the time of manufacture, and the curing conditions (temperature, time). Even when the resin is manufactured under the same manufacturing conditions, manufacturing variations may occur due to the surrounding temperature environment, temperature distribution in the structure, and the like, and the glass transition temperature may change.
  • the strength of the FRP structure may be reduced, leading to destruction. For this reason, in order to ensure the reliability of the FRP structure, it is necessary to evaluate the glass transition temperature and guarantee the necessary characteristics.
  • FRP depends on the direction of the reinforcing fiber, and generally has the highest strength against a load in the same direction as the fiber direction.
  • the load direction deviates from the fiber direction and the shape of the fiber is irregular, the strength against the load in the fiber direction is greatly reduced. For this reason, it is very important to carry out appropriate manufacturing control so that the fiber direction is aligned with the designed load direction so as not to cause irregular shape of the fiber.
  • the main causes of FRP strength decrease are the three items described above, such as a decrease in resin properties (elastic modulus, strength, etc.) due to a change in glass transition temperature, an irregular fiber shape, and a lack of fiber volume fraction. is there. If the strength of FRP is reduced by superimposing one or more of these, the product may not be used.
  • Conventional techniques for inspecting FRP include a method of measuring the propagation time of ultrasonic waves (for example, the method described in Patent Document 1) and a method of evaluating using the relationship between the group velocity and intensity of plate waves (for example, patents). There is a method described in Document 2. In addition, there is a method (for example, a method described in Patent Document 3) of performing deterioration diagnosis of a laminated product from the relationship between mechanical strength and hardness.
  • the ultrasonic wave may not pass through the deteriorated part of the subject, so there is a possibility that the deterioration cannot be reliably estimated.
  • the evaluation method using the relationship between the group velocity and intensity of the plate wave it is necessary to increase the distance between the measurement points in order to accurately measure the difference in the arrival time of the signals, and the local characteristics are evaluated. Difficult to do.
  • the surface of a large structure such as a wind turbine blade is not always flat, and the measurement point It is difficult to grasp the distance between them.
  • the method of diagnosing degradation of laminated products from the relationship between mechanical strength and hardness is mainly based on examination of FRP strength degradation due to the effects of resin degradation, and evaluates the deterioration of characteristics caused by other effects and their causes. The description about this is not seen, and the strength reduction due to the irregular shape of the fiber is not evaluated.
  • the problem to be solved by the present invention is to evaluate the characteristics of the FRP in order to ensure the reliability of the FRP structure, and to evaluate the FRP that can easily and accurately determine the strength reduction portion and the cause of the strength reduction. It is to provide a method and an evaluation device.
  • the FRP evaluation method basically has the following characteristics.
  • the elastic modulus of the subject FRP is measured for at least one examination temperature.
  • the compressive strength of the FRP is obtained.
  • the relationship between the temperature of the FRP and the compressive strength is obtained.
  • the relationship between the obtained temperature and compressive strength of the FRP and the relationship between the reference temperature and compressive strength obtained in advance are compared to determine at least one of the strength reduction of the FRP and the cause thereof.
  • the FRP evaluation apparatus basically has the following characteristics.
  • a device that measures the elastic modulus of the FRP that is the subject, a temperature adjusting device that adjusts the temperature of the elastic modulus measuring unit of the FRP, a storage device, and an arithmetic device are provided.
  • the storage device stores first reference data indicating a relationship between a predetermined elastic modulus and compressive strength, and second reference data indicating a relationship between a predetermined temperature and compressive strength.
  • the arithmetic device collates the elastic modulus of the FRP measured for at least one inspection temperature with the first reference data to obtain a relationship between the temperature of the FRP and the compressive strength.
  • the arithmetic device further compares at least one of the decrease in the strength of the FRP and the cause thereof by comparing the obtained relationship between the temperature and compressive strength of the FRP with the second reference data.
  • the present invention it is possible to evaluate the strength of each part of the FRP structure, find a strength-decreasing portion, and determine the cause of the strength reduction. Therefore, the reliability of the FRP structure can be ensured.
  • the FRP evaluation method and evaluation apparatus obtains a correlation between FRP characteristics and strength in advance (for example, a relationship as shown in FIG. 1 to be described later), and non-destructively determines the characteristics of FRP as a subject.
  • the correlation obtained in advance is compared with the measured characteristics, and the strength of the FRP as the subject is obtained.
  • the strength of the FRP is obtained for each inspection temperature in a predetermined inspection temperature range, and the relationship between the temperature and the strength (for example, the relationship shown in FIGS. 2 and 3 described later) is obtained from the result.
  • the inspection temperature may be at least one within the inspection temperature range. From the relationship between the temperature and the intensity, the cause of the decrease in the intensity of the FRP that is the subject can be determined.
  • the above process is performed for some inspection points within the inspection range, and the strength-decreasing portion of the FRP that is the subject is discriminated nondestructively.
  • the FRP evaluation method and evaluation apparatus it is possible to evaluate the local characteristics of FRP in a non-destructive manner even in a large structure such as a wind turbine blade whose surface is not necessarily flat, and to reliably estimate the deterioration of FRP. Can do.
  • the main causes of the decrease in strength of FRP are three items: a decrease in resin properties due to a change in glass transition temperature, an irregular shape of the fiber, and a shortage of fiber volume ratio (ratio of fiber to resin).
  • the deterioration of the resin characteristics leads to poor resin characteristics, and the irregular shape of the fibers and the insufficient volume ratio of the fibers lead to defective fiber structures.
  • FIG. 1 shows an example of the relationship between the elastic modulus in the laminating direction of the unidirectional reinforced laminated structure FRP and the compressive strength in the fiber direction (hereinafter also simply referred to as “strength”).
  • the relationship shown in FIG. 1 was obtained by a test conducted using FRP test pieces in which the fibers were glass and the resin was an epoxy resin. As shown in the parentheses of the legend in the figure, the test piece has two types of curing conditions (curing at 70 ° C. for 4 hours (insufficient resin curing condition) and curing at 70 ° C. for 16 hours (resin proper curing condition). ).
  • test pieces were tested in an inspection temperature range of 20 to 50 ° C., and the relationship between the elastic modulus in the lamination direction and the compressive strength in the fiber direction as shown in FIG. 1 was obtained. From the relationship of FIG. 1, it can be seen that there is a high correlation between the elastic modulus in the lamination direction and the compressive strength in the fiber direction.
  • the characteristics of such FRP laminates are determined by the composition of the FRP resin and the reinforcing fibers, and can be almost estimated by a composite law.
  • the compound rule is that each characteristic of the resin and the reinforcing fiber is reflected according to the ratio (volume ratio) existing in the FRP.
  • the fiber direction and lamination direction characteristics of the unidirectional reinforced laminated structure FRP are represented by the following formulas (1) and (2), respectively.
  • Formula (1) shows the characteristics of the composite material (that is, the characteristics of FRP) in the fiber direction
  • Formula (2) shows the characteristics in the lamination direction, respectively.
  • the composite material characteristic is represented by P c
  • the reinforcing fiber characteristic is represented by P f
  • the resin characteristic is represented by P m
  • the reinforcing fiber volume fraction is represented by V f .
  • the characteristic referred to here is an elastic modulus, a linear expansion coefficient, hardness, or the like, and may indicate strength in the fiber direction.
  • the characteristic P f of the fiber that is a reinforcing material is large, the characteristic P f of the fiber is dominant in the characteristic of the FRP (the characteristic P c of the composite material).
  • the resin property Pm is reduced, this relationship is established for the tensile load, but this effect is not necessarily established for the compression load because the effect of retaining the fiber by the resin is large. without, FRP properties (modulus, strength, etc.) decreases with the characteristic P m of the resin.
  • the characteristics P m of the resin is the dominant parameter in the FRP characteristics.
  • Tg glass transition temperature
  • the FRP characteristics have a high correlation with the resin characteristics in both the fiber direction and the lamination direction. Therefore, if the resin characteristics of the FRP structure can be evaluated, the FRP strength and elastic modulus can be estimated. be able to. It is difficult to evaluate the characteristics of the resin alone after forming the FRP.
  • the characteristics for example, elastic modulus
  • the strength of the FRP is estimated using the elastic modulus in the stacking direction of the FRP instead of the resin characteristics. be able to. That is, it is possible to estimate the strength of FRP by measuring the elastic modulus in the stacking direction of FRP.
  • the compressive strength in the fiber direction has a high correlation with the characteristics of the resin, the correlation between the elastic modulus in the stacking direction of FRP and the compressive strength in the fiber direction is also high.
  • FRP reinforced fibers not only unidirectionally reinforced, but also unidirectionally reinforced and woven fabrics. By extending the same concept, it is possible to analogize similar relationships with FIG. It is.
  • a correlation between the elastic modulus and strength of FRP, which is reference data, is obtained in advance. Specifically, using a properly manufactured FRP standard test piece, the elastic modulus in the lamination direction and the compressive strength in the fiber direction were measured under standard conditions, and the correlation between them as shown in FIG. Find the relationship in advance. The relationship between the elastic modulus and strength is used as reference data.
  • FIG. 2 is a diagram of a standard product and an FRP (resin defective product) with reduced resin characteristics
  • FIG. 3 is a diagram of a standard product and an FRP (structurally defective product) having a defective fiber structure. The relationship between the temperature and strength of the standard product is also used as reference data.
  • the correlation between the elastic modulus in the laminating direction and the compressive strength in the fiber direction, and the relationship between the temperature and the strength for the standard specimens and defective products of FRP as shown in FIGS. 1 to 3 are stored as a database. .
  • Defective due to deterioration of resin characteristics and defective fiber structure can be discriminated by examining the relationship between strength and temperature.
  • FIG. 2 is a diagram schematically showing the relationship between temperature and strength for FRP standard products and defective resin products.
  • the standard product of FRP shows a substantially constant strength at a temperature not higher than the glass transition temperature (Tg) determined by the characteristics of the resin.
  • Tg glass transition temperature
  • the strength begins to decrease as the temperature increases and near the glass transition temperature, and decreases significantly as the temperature increases. Therefore, the glass transition temperature of the resin needs to be higher than the use temperature range of the product.
  • the resin characteristics deteriorate for some reason and are not equal to the standard product, and when the glass transition temperature decreases, the strength decreases near the glass transition temperature. Therefore, by examining the temperature at which the strength has decreased and comparing it with the glass transition temperature of the standard product, it is possible to determine whether or not the resin characteristics have been decreased.
  • the cause of the deterioration of the resin characteristics may be a curing failure due to abnormal curing temperature or insufficient holding time, or in the case of a resin mixed with two liquids, a blending failure of the main agent and the curing agent.
  • a curing failure due to abnormal curing temperature or insufficient holding time or in the case of a resin mixed with two liquids, a blending failure of the main agent and the curing agent.
  • FIG. 3 is a diagram schematically showing the relationship between temperature and strength for FRP standard products and structurally defective products.
  • the structurally defective products have the same glass transition temperature as that of the standard products, but the strength tends to decrease as a whole at each temperature. Therefore, by comparing the strength at each temperature with a standard product, it is possible to determine the presence or absence of strength reduction due to a defective fiber structure.
  • the characteristic change due to the defective fiber structure is hardly affected by the temperature change, and therefore it is not necessary to adjust the temperature at the time of measurement.
  • the causes of the defective fiber structure include irregular shape of the fiber and insufficient volume ratio of the fiber.
  • the two-dimensional intensity distribution in the plane of the FRP structural member can be examined to determine whether the intensity is continuously changing gradually or whether there are scattered strength reduction parts (whether the intensity changes discontinuously). For example, it is possible to determine whether the cause of the defective fiber structure is irregular fiber shape or insufficient fiber volume ratio. If the strength is continuously changing, the shape of the fiber is irregular, and if the strength drop is scattered (the strength changes discontinuously), the fiber volume ratio is insufficient due to local internal defects. It can be determined that there is. Possible causes of local internal defects include an excessive amount of resin and voids. As described above, the in-plane two-dimensional intensity distribution of the FRP structural member can be estimated by measuring the elastic modulus of the FRP.
  • the size of the void varies depending on the dimensions of the structure and the manufacturing conditions, but is about several millimeters to several millimeters. In the case where the voids are not concentrated, the strength-decreasing portion is limited to the void size range.
  • the cause of the fiber structure failure is the irregular shape of the fiber
  • the thickness of the fiber sheet is required when the FRP structure is manufactured by laminating the fiber sheets. Since the length is about 1 mm, it becomes a considerably large irregularity. Therefore, the change in the thickness of the fiber sheet can be sufficiently confirmed visually.
  • a fiber having an irregular fiber shape wavelength of 10 mm or more may be used. In this case, the presence or absence of irregular shape of the fiber can be estimated from the continuous change in strength measured at regular intervals.
  • FRP reinforcing fibers usually use only one material in one structural member. This is because when a plurality of materials are used, the elastic modulus and the linear expansion coefficient are different, so that molding is difficult, and thermal stress may be generated due to a temperature change when the resin is cured. However, even when a plurality of materials are used for the reinforcing fiber of FRP, fibers of different types of materials (hereinafter referred to as “different materials”) are embedded in the main reinforcing fibers, and the amount of fibers of the different materials is determined. Such a problem is unlikely to occur if the minimum necessary for discriminating the shape irregularity is suppressed.
  • the fiber shape irregularity can be inspected. Since the fibers of different materials have different properties from the surrounding reinforcing fibers, the state of change in shape is also different. When shape irregularity (swell) occurs, it becomes easy to find this irregular shape. That is, when the shape of the fiber of the dissimilar material is changed, it can be easily determined that the FRP fiber has an irregular shape. In this way, the fibers of different materials can be used as the fibers for determining the irregular shape.
  • the color of the fiber of the different material may be different from the color of the reinforcing fiber. If the color of the fiber is different, it will be easier to identify different materials on the appearance, and it will be easier to see if there is an irregular shape. By examining the distribution of the undulations of different materials for the entire FRP structural member, the state of irregular shape of the reinforcing fibers can be evaluated in detail.
  • FIG. 4 is a schematic diagram for explaining a method of arranging dissimilar material fibers in the FRP structure.
  • the FRP structure includes an FRP structural member 3, and the FRP structural member 3 includes reinforcing fibers 1 and dissimilar fibers 2.
  • the dissimilar material fibers 2 may be embedded in at least one place in the FRP structural member 3 including the reinforcing fibers 1 in advance. If the dissimilar material fibers 2 are embedded in at least one place, it is possible to evaluate the irregular shape of the reinforcing fibers 1 for the entire FRP structural member 3. If you want to investigate the position and direction of irregular shapes in detail, if you increase the number of fibers 2 of dissimilar materials within the range where there is no problem in strength, it becomes possible to evaluate three-dimensional irregularities. Characteristic evaluation is possible.
  • the dissimilar material fiber 2 is more desirable as long as it is a material having a modulus of elasticity and a linear expansion coefficient close to those of the reinforcing fiber 1 and can be easily molded and can suppress the thermal stress generated when the resin is cured. Further, in the case of a structure used outdoors such as a windmill blade, it is desirable to use an insulating material in order to prevent damage due to lightning.
  • Insufficient fiber volume ratio is caused by the fact that unnecessary resin cannot be sufficiently discharged at the time of molding, and the amount of resin becomes excessive, or air remains as voids in the FRP. If the amount of the resin is excessive, the overall thickness and width will increase, so if these dimensions are examined and if they are larger than the standard dimensions, the resin amount is excessive. It can be judged. In addition, as described above, when the void is the cause, the size of the void is from several commas to several millimeters, and therefore, it is determined by checking whether or not strength reduction portions of this size are scattered. can do.
  • a database on the relationship between the elastic modulus and the strength can be provided. This database can be used to determine the cause of a defect in an evaluation process described later.
  • test specimens that reflect anticipated defects, and test specimens whose resin characteristics have deteriorated over time should also be used to determine the cause of defects by providing a database of those data. Can do.
  • FIG. 5 is a block diagram showing an embodiment of an evaluation apparatus to which the FRP evaluation method according to the present invention is applied.
  • the FRP evaluation apparatus according to the present embodiment includes a hardness meter 11, a temperature adjustment device 12, a calculation / determination device 13, a storage device 14, and a display device 15, and evaluates the FRP that is the subject 10.
  • the hardness meter 11 measures the elastic modulus of the subject 10.
  • an ultrasonic hardness meter or an ultrasonic flaw detector is suitable. This is a device that obtains an elastic modulus from the relationship between the contact radius of the contact at that time and the indentation depth by pressing the contact at the distal end against the surface of the subject 10. In this apparatus, since the evaluation can be performed in the range of elastic deformation of the subject 10, the evaluation can be performed without damaging the subject 10.
  • the ultrasonic hardness tester measures only a limited range near the surface of the specimen 10, the entire thickness direction cannot be evaluated, but conversely, since it is easily affected by the characteristics of the resin, the temperature characteristics of the resin It is suitable as an apparatus for evaluating
  • the ultrasonic flaw detector can check the presence or absence of foreign matter or internal defects in the subject 10 from the relationship between the incident wave and the reflected wave of the ultrasonic wave. Therefore, the presence or absence of shape irregularities can be examined by examining the condition of the fibers. In addition, evaluation of internal defects such as voids, and evaluation of the amount of resin by measuring the thickness of the subject 10 are also possible. Therefore, it can be checked whether or not the fiber volume ratio is insufficient, and it can be understood that the fiber volume ratio is insufficient when an internal defect exists or the amount of resin is large. By comparing these inspection results with the data stored in the database and determining which defect is present, the cause of the strength reduction can be estimated.
  • the temperature adjustment device 12 When investigating irregularities in the shape of the fiber, it is not necessary to change the temperature and measure, so the temperature adjustment device 12 need not be used. However, since the measured value of the thickness may change depending on the temperature, it is necessary to measure the temperature with the temperature adjusting device 12 and correct the measured value of the thickness.
  • the ultrasonic hardness meter and the ultrasonic flaw detector were illustrated here as the elastic modulus measuring device, a device capable of measuring the elastic modulus nondestructively such as a device using acoustic emission may be used. .
  • the temperature adjustment device 12 includes a thermometer and a heater, and measures and adjusts the temperature of the subject 10.
  • the measurement and adjustment of the temperature are performed on the elastic modulus measurement unit of the subject 10 and its surroundings.
  • the temperature adjustment may be performed at least in the range measured by the hardness meter 11 (predetermined inspection temperature range), and can be handled with a small scale.
  • the arithmetic / judgment device 13 compares the elastic modulus obtained by the hardness meter 11 with the database stored in the storage device 14 to obtain the strength of the subject 10. Further, the obtained intensity of the subject 10 is compared with the data stored in the database to derive the presence / absence of the defect and the estimation result of the defect cause. Moreover, the measurement position of the hardness meter 11 can be acquired and the intensity distribution of FRP can also be calculated
  • the storage device 14 includes a database for estimating the strength from the measurement result of the elastic modulus of the subject 10 and estimating the presence or absence of the subject 10 and the cause of the failure.
  • the database stores data on standard test pieces properly manufactured under standard conditions, test pieces manufactured by changing the fiber content, and test pieces manufactured by changing the resin curing conditions. Specifically, as shown in FIGS. 1 to 3, data on the relationship between the elastic modulus and strength at each temperature of the test piece, the relationship between the temperature and strength of the test piece, and the obtained glass transition temperature is provided. .
  • By providing a database of test pieces manufactured by changing parameters (such as fiber content and resin curing conditions) that may cause defects it is possible to improve the accuracy of estimation of the cause of defects.
  • the database may include only data for the standard test piece. Moreover, it is not necessary to provide data on parameters relating to defects that are unlikely to occur in manufacturing.
  • the display device 15 displays measurement results and evaluation results. For example, the measurement temperature, the value of the elastic modulus at each measurement temperature, the strength value obtained from the elastic modulus based on the data in the database, the glass transition temperature obtained from the relationship between temperature and strength, and the measurement results As a result of determining the presence or absence of a defect in comparison with the data, and if there is a defect, it is possible to display all or some of the estimated causes of the defect.
  • the calculation / determination device 13 executes calculations such as evaluation and discrimination described below.
  • the evaluation is performed for each predetermined inspection point in the FRP structure. In the following, the evaluation procedure for one inspection point will be described, but the overall evaluation of the FRP structure is performed for all the inspection points.
  • the elastic modulus of the FRP that is the subject 10 is measured using the hardness meter 11.
  • the temperature of the subject 10 is measured by a thermometer provided in the temperature control device 12.
  • the measured elastic modulus of the subject 10 is collated with the relationship between the elastic modulus and the strength of the database stored in the storage device 14 (the relationship as shown in FIG. 1) to obtain the strength of the subject 10.
  • the step of measuring the elastic modulus and obtaining the strength is performed for each inspection temperature within a predetermined inspection temperature range by changing the temperature of the subject 10 with the temperature control device 12. That is, the elastic modulus of the subject 10 is measured at each inspection temperature, and the strength at each inspection temperature of the subject 10 is obtained from the measured elastic modulus based on the relationship between the elastic modulus and the strength of the database. Thereby, the relationship between the temperature and intensity of the subject 10 (the relationship as shown in FIGS. 2 and 3) is obtained.
  • the glass transition temperature (Tg) is obtained from the relationship between the temperature and intensity of the subject 10.
  • the glass transition temperature (Tg) is determined as a point at which the strength starts to greatly decrease.
  • the glass transition temperature (Tg) can be determined and determined as a temperature at which the strength is reduced to 90% with respect to the strength at the reference temperature (room temperature). It can also be determined according to the measurement target (subject 10).
  • FIG. 6 is an example of a flow chart for determining whether the FRP defect is a defect due to a decrease in resin characteristics or a fiber structure defect.
  • FIG. 6 is a flowchart for one inspection point. When evaluating the entire FRP structure, the procedure shown in the flow of FIG. 6 is performed for each inspection point.
  • step 601 the intensity of the subject 10 (FRP) is compared with the standard intensity at all inspection temperatures within the inspection temperature range.
  • the standard strength is the strength of a standard test piece (standard product), and is stored in a database provided in the storage device 14 as described above.
  • the strength of FRP is equal to or higher than the standard strength at all inspection temperatures, the inspection of the characteristics of the current inspection point is determined to be acceptable.
  • step 601 If not passed in step 601, the current inspection point is judged to be defective because the strength is low (elastic modulus is low), and the process proceeds to step 602.
  • the glass transition temperature (Tg) is evaluated in order to determine the cause of the failure.
  • the glass transition temperature of the specimen 10 is lower than the glass transition temperature (standard value) of the standard test piece, the resin characteristics deteriorate due to poor blending of the resin (including non-uniform distribution due to poor stirring, etc.) or poor curing conditions. Presumed to be the main cause of the failure (step 603).
  • the glass transition temperature (standard value) of the standard test piece is stored in a database provided in the storage device 14.
  • the glass transition temperature is not different from the standard value, and when the strength of the specimen 10 is lower than the standard strength at all the test temperatures within the test temperature range, the cause other than the deterioration of the resin characteristics, that is, the fiber structure is defective. (Step 604).
  • the main causes of the defective fiber structure are the irregular shape of the fiber and the insufficient volume ratio of the fiber.
  • the most likely cause of a defective fiber structure is a fiber volume ratio deficiency in which the volume ratio of fibers having a higher elastic modulus than the resin is less than the volume ratio deficiency of the standard specimen. In this case, it is considered that the volume ratio is insufficient due to defective molding due to insufficient pressure during molding or insufficient evacuation and voids remaining in the composite material (FRP).
  • FRP composite material
  • the measurement for discriminating between the irregular shape of the fiber and the insufficient volume ratio of the fiber is performed for a plurality of inspection points of the subject 10, and the relationship between the position and intensity of each inspection point is examined.
  • the resulting intensity distribution state With a database stored in the storage device 14, it is examined whether the intensity changes continuously due to fiber irregularity or discontinuously due to voids.
  • FIG. 7 is for determining whether the defect of FRP is a defect due to the deterioration of the resin characteristics or the defect of the fiber structure, and further, determining whether the cause of the defect of the fiber structure is an irregular shape of the fiber or an insufficient volume ratio of the fiber. It is an example of the flowchart of this.
  • an ultrasonic flaw detector is used as the hardness meter 11, and after determining the irregularity of the FRP fiber shape and the presence or absence of voids, the test results are evaluated by the discrimination flow shown in FIG.
  • FIG. 7 is a flowchart for one inspection point, as in FIG. 6. For the entire FRP structure, the procedure shown in the flow of FIG. 7 is performed for each inspection point.
  • an ultrasonic hardness tester is used as the hardness tester 11, and the processing from step 701 to step 703 is performed.
  • the processing from Step 701 to Step 703 corresponds to the processing from Step 601 to Step 603 shown in FIG. 6, and the same processing as Step 601 to Step 603 is performed.
  • step 703 if the glass transition temperature is not different from the standard value and the strength of the specimen 10 is lower than the standard strength, it can be considered as a cause other than the deterioration of the resin properties, that is, the defect of the fiber structure. Proceed to
  • step 704 if there is irregularity (swell) in the fiber, it is determined that the decrease in the strength of the FRP is caused by irregularity in the fiber (step 705).
  • the presence / absence of the irregular shape of the fiber can be determined by the method for examining the presence / absence of the irregular shape of the fiber described above.
  • step 706 If there is no irregularity (swell) in the shape of the fiber, it is determined that the decrease in the strength of the FRP is caused by a shortage of the fiber volume ratio (step 706). Insufficient fiber volume fraction can also be determined by examining whether the strength changes discontinuously due to voids or the like.
  • the cause of FRP failure can be determined by evaluating the deterioration of the resin characteristics, the irregular shape of the fiber, or the insufficient volume ratio of the fiber. Therefore, by using the FRP evaluation method and evaluation apparatus according to the present invention, it is possible to easily determine whether or not the strength of the FRP is reduced and the cause thereof, and to manufacture a highly reliable FRP structure.
  • the evaluation method described above is a method mainly used for evaluating the initial characteristics of the FRP structure.
  • the present invention can also be used to evaluate changes over time in the properties of FRP structures.
  • FRP resin tends to deteriorate over time due to long-term operation, and the strength tends to decrease. Moreover, when it is used for a member that receives repeated loads, the strength is reduced due to fatigue. These strength reductions may occur separately or may overlap. Therefore, the remaining life of the FRP structure can be evaluated by periodically measuring the change in strength with the elapsed time or the number of repetitions of the portion where the strength is most significantly reduced in the FRP structure.
  • FIG. 8 is a diagram showing an example of a change in strength due to the elapsed time of the FRP structure. As shown in FIG. 8, the intensity decreases with the elapsed time.
  • FIG. 9 is a diagram showing an example of the relationship between the number of repetitions and the strength when a constant load is repeatedly applied to the FRP structure.
  • a standard product standard test piece
  • a structurally defective product FRP having a defective fiber structure
  • the structurally defective product has a greater decrease in strength with respect to the increase in the number of repetitions than the standard product.
  • the strength of FRP varies depending on the angle of the fiber, and the rate of decrease is particularly high in a defective part where the fiber has irregular shape (swells). This is because a strain is concentrated due to shape irregularity (swell), and the fatigue characteristics change due to local concentration of stress, so that a decrease in strength due to fatigue tends to be remarkable at the irregular shape. Therefore, even if the resulting shape irregularity is acceptable in the initial evaluation, the secular change may be more noticeable than the portion without shape irregularity. Periodic evaluations are necessary.
  • FIG. 10 is a diagram illustrating an example of a configuration for performing the above-described evaluation method for each inspection point within the inspection range of the FRP structure.
  • the upper view of FIG. 10 is a side view, and the lower view is a top view.
  • the subject 10 has a rectangular top surface shape.
  • the characteristic (elastic modulus) of the subject 10 is measured while moving the portion having the hardness meter 11 in the evaluation apparatus in the longitudinal direction of the subject 10 (left-right direction in FIG. 10).
  • the evaluation apparatus includes a mechanism for moving the hardness meter 11 in the width direction of the subject 10 (the vertical direction in the lower diagram of FIG. 10), and can measure the characteristics in the width direction of the subject 10. Therefore, the hardness meter 11 can scan the surface of the subject 10 two-dimensionally and measure the characteristics.
  • the evaluation apparatus measures the characteristics at each inspection point on the surface of the subject 10.
  • the storage device 14 (see FIG. 5, not shown in FIG. 10) stores a plurality of measurement data such as the position coordinates of the inspection point, the elastic modulus at each temperature, the fiber direction, the presence or absence of voids, and the plate thickness. Let The measurement data is calculated by the calculation / judgment device 13 (see FIG. 5, not shown in FIG. 10), and the result is evaluated to determine the presence / absence of a defect and its position.
  • FIG. 10 shows an evaluation apparatus having a mechanism in which the upper surface shape of the FRP structure (subject 10) is rectangular and the hardness meter 11 is scanned in two orthogonal directions, but this evaluation apparatus is shown in this example.
  • a scanning mechanism suitable for the shape of the FRP structure can be provided.
  • the FRP structure is spherical, it can have a mechanism for scanning along the spherical surface.
  • the present invention can also be applied to FRPs having other reinforced structures.
  • it is suitable for FRP having a laminated structure.

Abstract

Disclosed are a fiber reinforced plastic (FRP) evaluation method and evaluation device, by which a strength degradation section and the cause of the strength degradation can be easily and highly accurately determined by nondestructively performing FRP characterization. The elastic modulus of the FRP which is a subject is measured in terms of at least one test temperature. The compression strength of the FRP is obtained by comparing the measured elastic modulus of the FRP with the previously obtained relationship between reference elastic modulus and compression strength. This obtains the relationship between the temperature and compression strength of the FRP. At least one of the strength degradation of the FRP or the cause thereof is determined by comparing the obtained relationship between the temperature and compression strength of the FRP with the previously obtained relationship between the reference temperature and compression strength.

Description

ＦＲＰの評価方法および評価装置FRP evaluation method and evaluation apparatus
　本発明は、各種機器の構造部材として用いられるＦＲＰの評価方法と評価装置に関し、より詳細には、非破壊の検査でＦＲＰの強度評価を行う方法と装置に関する。 The present invention relates to an evaluation method and an evaluation apparatus for FRP used as a structural member of various devices, and more particularly to a method and an apparatus for evaluating the strength of FRP by non-destructive inspection.
　ＦＲＰ（Fiber Reinforced Plastics）は、高い強度と弾性率を持つ強化繊維（ガラス、炭素など）を、樹脂を含浸させて固めたものである。比強度が高いという特徴を持つため、各種機器の構造部材として広く使用されている。ＦＲＰは扱いやすいため、大型の構造物を製作する際には、予めシート状にした繊維を型に合わせて積層していき樹脂を塗りこむ、またはシート状にした繊維に樹脂を浸み込ませた状態で型に積層していく、という方法で製作されることが多い。 FRP (Fiber Reinforced Plastics) is made by impregnating a resin with a reinforcing fiber (glass, carbon, etc.) having high strength and elastic modulus. Because of its high specific strength, it is widely used as a structural member for various devices. Since FRP is easy to handle, when manufacturing large structures, sheet-like fibers are laminated in accordance with the mold, and then the resin is applied, or the resin is soaked in the sheet-like fibers. It is often manufactured by the method of stacking on a mold in the state of being.
　樹脂には、ガラス転移温度（Ｔｇ）と呼ばれる特性が大きく変化する温度があり、この温度以上になると、樹脂の弾性率や強度は急激に低下する。この温度は、樹脂の種類や製造時の配合比や硬化条件（温度、時間）など、様々な要因によって変化する。樹脂を同じ製造条件で製作した場合でも、周囲の温度環境や構造物の中の温度分布などにより、製造ばらつきが生じ、ガラス転移温度が変化する場合がある。 Resins have a temperature at which the characteristic called the glass transition temperature (Tg) changes greatly. When the temperature is higher than this temperature, the elastic modulus and strength of the resin rapidly decrease. This temperature varies depending on various factors such as the type of resin, the blending ratio at the time of manufacture, and the curing conditions (temperature, time). Even when the resin is manufactured under the same manufacturing conditions, manufacturing variations may occur due to the surrounding temperature environment, temperature distribution in the structure, and the like, and the glass transition temperature may change.
　使用環境の温度がガラス転移温度の付近、またはガラス転移温度を上回る場合には、ＦＲＰ構造物の強度が低下し破壊に至る可能性がある。このため、ＦＲＰ構造物の信頼性を確保するためには、ガラス転移温度を評価し、必要な特性を保証する必要がある。 If the temperature of the usage environment is near the glass transition temperature or exceeds the glass transition temperature, the strength of the FRP structure may be reduced, leading to destruction. For this reason, in order to ensure the reliability of the FRP structure, it is necessary to evaluate the glass transition temperature and guarantee the necessary characteristics.
　また、ＦＲＰは、強度が強化繊維の方向に依存し、一般的に繊維方向と同一の方向の負荷に対して最も高い強度を有する。しかし、高い異方性を持つため、負荷方向が繊維方向からずれて繊維の形状不整が起こると、繊維方向の負荷に対する強度は大きく低下する。そのため、繊維の形状不整が起こらないように、適切な製造管理をして、設計された負荷方向に繊維方向を合わせて製造することが非常に重要となる。 Further, FRP depends on the direction of the reinforcing fiber, and generally has the highest strength against a load in the same direction as the fiber direction. However, since it has high anisotropy, when the load direction deviates from the fiber direction and the shape of the fiber is irregular, the strength against the load in the fiber direction is greatly reduced. For this reason, it is very important to carry out appropriate manufacturing control so that the fiber direction is aligned with the designed load direction so as not to cause irregular shape of the fiber.
　また、ＦＲＰの成形時には、真空注入などにより、ＦＲＰ内の樹脂が過大な部分やボイドをなくすような製造方法が用いられるが、これが不十分な場合には、全体として繊維の比率（体積率）が不足するため、強度低下の要因となる。 Further, when molding FRP, a manufacturing method is used in which the resin in the FRP is removed by excessive injection or voids by vacuum injection or the like, but if this is insufficient, the fiber ratio (volume ratio) as a whole This is a cause of strength reduction.
　ＦＲＰの強度低下の要因の主なものは、上述したような、ガラス転移温度の変化による樹脂特性（弾性率や強度など）の低下、繊維の形状不整、および繊維の体積率不足の３項目である。これらのうちの一つ、または複数が重畳することによりＦＲＰの強度が低下すると、製品として使用できない場合がある。 The main causes of FRP strength decrease are the three items described above, such as a decrease in resin properties (elastic modulus, strength, etc.) due to a change in glass transition temperature, an irregular fiber shape, and a lack of fiber volume fraction. is there. If the strength of FRP is reduced by superimposing one or more of these, the product may not be used.
　そのため、このような強度低下がないかを検査して評価することが、ＦＲＰ構造物の信頼性を保証する上で重要となる。 Therefore, it is important to inspect and evaluate whether or not there is such a decrease in strength in order to guarantee the reliability of the FRP structure.
　ＦＲＰを検査する従来技術としては、超音波の伝搬時間を測定する方法（例えば、特許文献１に記載の方法）や、板波の群速度と強度の関係を用いて評価する方法（例えば、特許文献２に記載の方法）がある。また、機械強度と硬度の関係から積層品の劣化診断を行う方法（例えば、特許文献３に記載の方法）などもある。 Conventional techniques for inspecting FRP include a method of measuring the propagation time of ultrasonic waves (for example, the method described in Patent Document 1) and a method of evaluating using the relationship between the group velocity and intensity of plate waves (for example, patents). There is a method described in Document 2. In addition, there is a method (for example, a method described in Patent Document 3) of performing deterioration diagnosis of a laminated product from the relationship between mechanical strength and hardness.
特開平１１－３３７５３２号公報JP 11-337532 A 特開２００４－１１７０３５号公報JP 2004-1117035 A 特開平６－３３１５２３号公報JP-A-6-331523
　ＦＲＰ構造物、特に風車翼などの大型構造物では、ＦＲＰ各部の強度を評価して強度が低下している部分を発見し、強度低下の原因を判別することが、信頼性を確保するために必要である。 In order to ensure the reliability of FRP structures, especially large structures such as wind turbine blades, it is possible to evaluate the strength of each part of the FRP to find a portion where the strength is reduced and determine the cause of the strength reduction. is necessary.
　超音波の伝搬時間を測定する方法では、超音波の種類および周波数によっては、被検体の劣化している部位を超音波が透過しないことがあるため、劣化を確実に推定できない可能性がある。板波の群速度と強度の関係を用いて評価する方法では、信号の到達時間の差を精度良く測定するためには、測定点間の距離を長くする必要があり、局所的な特性を評価することが難しい。また、いずれの測定法でも２点の測定点間の距離を正確に把握することが精度を確保するために必要であるが、風車翼などの大型構造物では表面が必ずしも平坦ではなく、測定点間の距離を把握するのが困難である。 In the method of measuring the propagation time of the ultrasonic wave, depending on the type and frequency of the ultrasonic wave, the ultrasonic wave may not pass through the deteriorated part of the subject, so there is a possibility that the deterioration cannot be reliably estimated. In the evaluation method using the relationship between the group velocity and intensity of the plate wave, it is necessary to increase the distance between the measurement points in order to accurately measure the difference in the arrival time of the signals, and the local characteristics are evaluated. Difficult to do. In any measurement method, it is necessary to accurately grasp the distance between two measurement points in order to ensure accuracy. However, the surface of a large structure such as a wind turbine blade is not always flat, and the measurement point It is difficult to grasp the distance between them.
　また、機械強度と硬度の関係から積層品の劣化診断を行う方法は、主に樹脂の劣化の影響によるＦＲＰの強度劣化について検討したものであり、他の影響による特性低下やその原因を評価することについての記載は見られず、繊維の形状不整などによる強度低下については評価対象としていない。 In addition, the method of diagnosing degradation of laminated products from the relationship between mechanical strength and hardness is mainly based on examination of FRP strength degradation due to the effects of resin degradation, and evaluates the deterioration of characteristics caused by other effects and their causes. The description about this is not seen, and the strength reduction due to the irregular shape of the fiber is not evaluated.
　本発明が解決しようとする課題は、ＦＲＰ構造物の信頼性を確保するために、ＦＲＰの特性評価を行い、強度低下部および強度低下の原因を簡易に精度良く判別することができるＦＲＰの評価方法および評価装置を提供することである。 The problem to be solved by the present invention is to evaluate the characteristics of the FRP in order to ensure the reliability of the FRP structure, and to evaluate the FRP that can easily and accurately determine the strength reduction portion and the cause of the strength reduction. It is to provide a method and an evaluation device.
　本発明によるＦＲＰの評価方法は、基本的には以下のような特徴を持つ。被検体であるＦＲＰの弾性率を、少なくとも一つの検査温度について測定する。測定した前記ＦＲＰの弾性率を、予め求めておいた参照用の弾性率と圧縮強度との関係と照合することにより、前記ＦＲＰの圧縮強度を求める。これにより、前記ＦＲＰの温度と圧縮強度との関係を求める。求めた前記ＦＲＰの温度と圧縮強度との関係と、予め求めておいた参照用の温度と圧縮強度との関係を比較して、前記ＦＲＰの強度低下およびその原因の少なくとも一つを判別する。 The FRP evaluation method according to the present invention basically has the following characteristics. The elastic modulus of the subject FRP is measured for at least one examination temperature. By comparing the measured elastic modulus of the FRP with the relationship between the elastic modulus for reference obtained in advance and the compressive strength, the compressive strength of the FRP is obtained. Thereby, the relationship between the temperature of the FRP and the compressive strength is obtained. The relationship between the obtained temperature and compressive strength of the FRP and the relationship between the reference temperature and compressive strength obtained in advance are compared to determine at least one of the strength reduction of the FRP and the cause thereof.
　また、本発明によるＦＲＰの評価装置は、基本的には以下のような特徴を持つ。被検体であるＦＲＰの弾性率を測定する装置と、前記ＦＲＰの弾性率測定部の温度を調節する温度調節装置と、記憶装置と、演算装置とを備える。前記記憶装置は、予め求めた弾性率と圧縮強度との関係を示す第１の参照用データと、予め求めた温度と圧縮強度との関係とを示す第２の参照用データとを記憶する。前記演算装置は、少なくとも一つの検査温度について測定した前記ＦＲＰの弾性率を第１の参照用データと照合して、前記ＦＲＰの温度と圧縮強度との関係を求める。前記演算装置は、さらに、求めた前記ＦＲＰの温度と圧縮強度との関係と第２の参照用データとを比較して、前記ＦＲＰの強度低下およびその原因の少なくとも一つを判別する。 The FRP evaluation apparatus according to the present invention basically has the following characteristics. A device that measures the elastic modulus of the FRP that is the subject, a temperature adjusting device that adjusts the temperature of the elastic modulus measuring unit of the FRP, a storage device, and an arithmetic device are provided. The storage device stores first reference data indicating a relationship between a predetermined elastic modulus and compressive strength, and second reference data indicating a relationship between a predetermined temperature and compressive strength. The arithmetic device collates the elastic modulus of the FRP measured for at least one inspection temperature with the first reference data to obtain a relationship between the temperature of the FRP and the compressive strength. The arithmetic device further compares at least one of the decrease in the strength of the FRP and the cause thereof by comparing the obtained relationship between the temperature and compressive strength of the FRP with the second reference data.
　本発明によれば、ＦＲＰ構造物の各部の強度を評価して、強度低下部を発見し、強度低下の原因を判別することができる。従って、ＦＲＰ構造物の信頼性を確保することができる。 According to the present invention, it is possible to evaluate the strength of each part of the FRP structure, find a strength-decreasing portion, and determine the cause of the strength reduction. Therefore, the reliability of the FRP structure can be ensured.
ＦＲＰの積層方向の弾性率と繊維方向の圧縮強度との関係の例を示す図である。It is a figure which shows the example of the relationship between the elastic modulus of the lamination direction of FRP, and the compressive strength of a fiber direction. ＦＲＰの標準品と樹脂不良品についての、温度と強度との関係の例を示す図である。It is a figure which shows the example of the relationship between temperature and intensity | strength about the standard product of FRP, and the resin defective product. ＦＲＰの標準品と構造不良品についての、温度と強度との関係の例を示す図である。It is a figure which shows the example of the relationship between temperature and intensity | strength about the standard goods and structural defect goods of FRP. 異種材の繊維をＦＲＰ構造物内に配置する方法を説明するための模式図である。It is a schematic diagram for demonstrating the method to arrange | position the fiber of a dissimilar material in a FRP structure. 本発明によるＦＲＰの評価装置の一実施例を示す構成図である。It is a block diagram which shows one Example of the evaluation apparatus of FRP by this invention. ＦＲＰの不良原因が、樹脂特性の低下か繊維構造の不良かを判別するためのフロー図の一例である。It is an example of the flowchart for discriminate | determining whether the defect cause of FRP is the fall of a resin characteristic or the defect of a fiber structure. ＦＲＰの不良原因が、樹脂特性の低下か、繊維の形状不整か、繊維の体積率不足かを判別するためのフロー図の一例である。It is an example of the flowchart for discriminating whether the defect cause of FRP is the deterioration of the resin characteristics, the irregular shape of the fiber, or the insufficient volume ratio of the fiber. ＦＲＰ構造物の経過時間による強度の変化例を示す図である。It is a figure which shows the example of a change of the intensity | strength by the elapsed time of a FRP structure. ＦＲＰ構造物に一定負荷を繰り返しかけた場合の、繰り返し回数と強度の関係の例を示す図である。It is a figure which shows the example of the relationship between the frequency | count of repetition and intensity | strength when a fixed load is repeatedly applied to a FRP structure. ＦＲＰ構造物の検査範囲内の各検査点について、本発明による評価方法を実施するための構成の一例を説明する図である。It is a figure explaining an example of the composition for carrying out the evaluation method by the present invention about each inspection point in the inspection range of an FRP structure.
　本発明によるＦＲＰの評価方法および評価装置は、ＦＲＰの特性と強度との相関関係（例えば、後述する図１に示すような関係）を予め求めておき、被検体であるＦＲＰの特性を非破壊で測定し、予め求めた相関関係と測定した特性とを照合し、被検体であるＦＲＰの強度を求める。ＦＲＰの強度は、予め定めた検査温度範囲の各検査温度について求め、この結果から温度と強度との関係（例えば、後述する図２、図３に示すような関係）を求める。検査温度は、検査温度範囲内に少なくとも一つあればよい。この温度と強度との関係から、被検体であるＦＲＰの強度低下の原因を判別することができる。以上の工程を、検査範囲内の何点かの検査点について行い、被検体であるＦＲＰの強度低下部を非破壊で判別する。 The FRP evaluation method and evaluation apparatus according to the present invention obtains a correlation between FRP characteristics and strength in advance (for example, a relationship as shown in FIG. 1 to be described later), and non-destructively determines the characteristics of FRP as a subject. The correlation obtained in advance is compared with the measured characteristics, and the strength of the FRP as the subject is obtained. The strength of the FRP is obtained for each inspection temperature in a predetermined inspection temperature range, and the relationship between the temperature and the strength (for example, the relationship shown in FIGS. 2 and 3 described later) is obtained from the result. The inspection temperature may be at least one within the inspection temperature range. From the relationship between the temperature and the intensity, the cause of the decrease in the intensity of the FRP that is the subject can be determined. The above process is performed for some inspection points within the inspection range, and the strength-decreasing portion of the FRP that is the subject is discriminated nondestructively.
　本発明によるＦＲＰの評価方法および評価装置によれば、表面が必ずしも平坦ではない風車翼などの大型構造物でもＦＲＰの局所的な特性を非破壊で評価でき、ＦＲＰの劣化を確実に推定することができる。 According to the FRP evaluation method and evaluation apparatus according to the present invention, it is possible to evaluate the local characteristics of FRP in a non-destructive manner even in a large structure such as a wind turbine blade whose surface is not necessarily flat, and to reliably estimate the deterioration of FRP. Can do.
　ＦＲＰの強度低下の原因の主なものは、ガラス転移温度の変化による樹脂特性の低下、繊維の形状不整、および繊維の体積率（樹脂に対する繊維の比率）不足の３項目である。樹脂特性の低下は、樹脂特性の不良を招き、繊維の形状不整および繊維の体積率不足は、繊維構造の不良を招く。 The main causes of the decrease in strength of FRP are three items: a decrease in resin properties due to a change in glass transition temperature, an irregular shape of the fiber, and a shortage of fiber volume ratio (ratio of fiber to resin). The deterioration of the resin characteristics leads to poor resin characteristics, and the irregular shape of the fibers and the insufficient volume ratio of the fibers lead to defective fiber structures.
　以下、本発明の実施例について説明する。なお、ＦＲＰの特性としては、弾性率、線膨脹係数、または硬度などを用いることができる。以下の実施例では、弾性率をＦＲＰの特性として用いた例について説明する。また、以下の実施例では、ＦＲＰの例として、積層構造の一方向強化ＦＲＰを用いた例について説明する。 Hereinafter, examples of the present invention will be described. As the characteristics of FRP, elastic modulus, linear expansion coefficient, hardness, or the like can be used. In the following examples, an example in which the elastic modulus is used as a characteristic of FRP will be described. In the following examples, an example using a unidirectional reinforced FRP having a laminated structure will be described as an example of FRP.
　図１に、一方向強化積層構造ＦＲＰの積層方向の弾性率と繊維方向の圧縮強度（以下、単に「強度」とも称する）との関係の例を示す。図１に示した関係は、繊維がガラスで樹脂がエポキシ樹脂のＦＲＰの試験片を用いて行った試験により得られた。試験片は、図内の凡例のカッコ内に示すように、二種類の硬化条件（７０℃で４時間の硬化（樹脂硬化不足条件）と、７０℃で１６時間の硬化（樹脂適正硬化条件））で作成した。これらの試験片を２０～５０℃の検査温度範囲で試験し、図１に示すような積層方向の弾性率と繊維方向の圧縮強度との関係を求めた。図１の関係から、積層方向の弾性率と繊維方向の圧縮強度との間には高い相関性があることが分かる。 FIG. 1 shows an example of the relationship between the elastic modulus in the laminating direction of the unidirectional reinforced laminated structure FRP and the compressive strength in the fiber direction (hereinafter also simply referred to as “strength”). The relationship shown in FIG. 1 was obtained by a test conducted using FRP test pieces in which the fibers were glass and the resin was an epoxy resin. As shown in the parentheses of the legend in the figure, the test piece has two types of curing conditions (curing at 70 ° C. for 4 hours (insufficient resin curing condition) and curing at 70 ° C. for 16 hours (resin proper curing condition). ). These test pieces were tested in an inspection temperature range of 20 to 50 ° C., and the relationship between the elastic modulus in the lamination direction and the compressive strength in the fiber direction as shown in FIG. 1 was obtained. From the relationship of FIG. 1, it can be seen that there is a high correlation between the elastic modulus in the lamination direction and the compressive strength in the fiber direction.
　このようなＦＲＰの積層材の特性は、ＦＲＰの樹脂と強化繊維の構成により決まり、複合則によりほぼ推定が可能である。複合則とは、樹脂と強化繊維のそれぞれの特性が、ＦＲＰの中に存在する比率（体積率）に応じて反映されるというものである。 The characteristics of such FRP laminates are determined by the composition of the FRP resin and the reinforcing fibers, and can be almost estimated by a composite law. The compound rule is that each characteristic of the resin and the reinforcing fiber is reflected according to the ratio (volume ratio) existing in the FRP.
　一方向強化積層構造ＦＲＰについての繊維方向および積層方向の特性は、それぞれ以下の式（１）、（２）で示される。式（１）は繊維方向についての、式（２）は積層方向についての複合材料の特性（すなわち、ＦＲＰの特性）を、それぞれ示している。式（１）、（２）において、複合材料の特性をＰｃ、強化繊維の特性をＰｆ、樹脂の特性をＰｍ、強化繊維の体積率をＶｆで表す。なお、ここでいう特性とは、弾性率、線膨脹係数、または硬度などであり、繊維方向については強度を示すこともある。 The fiber direction and lamination direction characteristics of the unidirectional reinforced laminated structure FRP are represented by the following formulas (1) and (2), respectively. Formula (1) shows the characteristics of the composite material (that is, the characteristics of FRP) in the fiber direction, and Formula (2) shows the characteristics in the lamination direction, respectively. In the formulas (1) and (2), the composite material characteristic is represented by P c , the reinforcing fiber characteristic is represented by P f , the resin characteristic is represented by P m , and the reinforcing fiber volume fraction is represented by V f . The characteristic referred to here is an elastic modulus, a linear expansion coefficient, hardness, or the like, and may indicate strength in the fiber direction.
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000002
 　式（１）に示すように、繊維方向では、強化材である繊維の特性Ｐｆが大きいため、繊維の特性ＰｆがＦＲＰの特性（複合材料の特性Ｐｃ）の中では支配的となる。但し、樹脂の特性Ｐｍが低下した場合、引張負荷に対してはこの関係が成立するが、圧縮負荷に対しては、樹脂による繊維を保持する効果の影響が大きいため、この関係は必ずしも成立せず、ＦＲＰの特性（弾性率、強度など）は、樹脂の特性Ｐｍに伴って低下する。
Figure JPOXMLDOC01-appb-M000002
 As shown in the formula (1), in the fiber direction, since the characteristic P f of the fiber that is a reinforcing material is large, the characteristic P f of the fiber is dominant in the characteristic of the FRP (the characteristic P c of the composite material). . However, when the resin property Pm is reduced, this relationship is established for the tensile load, but this effect is not necessarily established for the compression load because the effect of retaining the fiber by the resin is large. without, FRP properties (modulus, strength, etc.) decreases with the characteristic P m of the resin.
　一方、式（２）に示すように、積層方向では、樹脂の特性Ｐｍのほうが小さいため、樹脂の特性ＰｍがＦＲＰの特性の中では支配的なパラメータとなる。特に、ガラス転移温度（Ｔｇ）を超えるような温度では、樹脂により繊維を保持する効果が期待できないため、弾性率は大きく低下し、これに伴ってＦＲＰの特性も低下する。 On the other hand, as shown in equation (2), in the stacking direction, for better characteristics P m of the resin is small, the characteristics P m of the resin is the dominant parameter in the FRP characteristics. In particular, at a temperature exceeding the glass transition temperature (Tg), since the effect of holding the fiber with the resin cannot be expected, the elastic modulus is greatly reduced, and the characteristics of the FRP are also lowered accordingly.
　このように、ＦＲＰの特性、特に強度および弾性率は、繊維方向、積層方向ともに樹脂の特性と高い相関を持つため、ＦＲＰ構造物の樹脂特性を評価できれば、ＦＲＰの強度と弾性率を推定することができる。ＦＲＰを形成した後で樹脂単独の特性を評価するのは、困難である。しかし、上述のように、ＦＲＰの積層方向の特性（例えば弾性率）は、樹脂の特性と相関が高いため、樹脂特性の代わりにＦＲＰの積層方向の弾性率を用いてＦＲＰの強度を推定することができる。すなわち、ＦＲＰの積層方向の弾性率を測定することにより、ＦＲＰの強度を推定することが可能である。特に、繊維方向の圧縮強度は、樹脂の特性との相関が高いため、ＦＲＰの積層方向の弾性率と繊維方向の圧縮強度との相関も高くなっている。 As described above, the FRP characteristics, particularly strength and elastic modulus, have a high correlation with the resin characteristics in both the fiber direction and the lamination direction. Therefore, if the resin characteristics of the FRP structure can be evaluated, the FRP strength and elastic modulus can be estimated. be able to. It is difficult to evaluate the characteristics of the resin alone after forming the FRP. However, as described above, the characteristics (for example, elastic modulus) in the stacking direction of the FRP have a high correlation with the characteristics of the resin. Therefore, the strength of the FRP is estimated using the elastic modulus in the stacking direction of the FRP instead of the resin characteristics. be able to. That is, it is possible to estimate the strength of FRP by measuring the elastic modulus in the stacking direction of FRP. In particular, since the compressive strength in the fiber direction has a high correlation with the characteristics of the resin, the correlation between the elastic modulus in the stacking direction of FRP and the compressive strength in the fiber direction is also high.
　ＦＲＰの強化繊維には、一方向強化だけでなく、二方向強化や織物構造のものなど種々あるが、いずれも同様の考え方を拡張することで、図１と類似の関係を類推することが可能である。 There are various types of FRP reinforced fibers, not only unidirectionally reinforced, but also unidirectionally reinforced and woven fabrics. By extending the same concept, it is possible to analogize similar relationships with FIG. It is.
　このような評価法を用いて、ＦＲＰの強度低下の原因を判別する方法について以下に説明する。 A method for discriminating the cause of the FRP strength decrease using such an evaluation method will be described below.
　まず、樹脂特性の低下について評価する方法を示す。 First, a method for evaluating the deterioration of resin characteristics will be described.
　初めに、基準となるデータである、ＦＲＰの弾性率と強度との相関関係を予め求める。具体的には、適正に製作されたＦＲＰの標準試験片を用いて、標準的な条件で、積層方向の弾性率と繊維方向の圧縮強度を測定し、図１に示したような両者の相関関係を予め求める。この弾性率と強度との関係を、参照用のデータとして用いる。 First, a correlation between the elastic modulus and strength of FRP, which is reference data, is obtained in advance. Specifically, using a properly manufactured FRP standard test piece, the elastic modulus in the lamination direction and the compressive strength in the fiber direction were measured under standard conditions, and the correlation between them as shown in FIG. Find the relationship in advance. The relationship between the elastic modulus and strength is used as reference data.
　このとき、ＦＲＰの標準試験片の温度を変えた場合についても、同様の相関関係を調べておき、検査温度範囲での温度と強度との関係を求める。図２と図３は、検査温度範囲での、ＦＲＰの標準試験片（標準品）および不良品の温度と強度との関係の例を示す図である。図２は、標準品と樹脂特性が低下したＦＲＰ（樹脂不良品）についての、図３は、標準品と繊維構造が不良であるＦＲＰ（構造不良品）についての図である。標準品の温度と強度との関係も、参照用のデータとして用いる。 At this time, even when the temperature of the FRP standard test piece is changed, the same correlation is examined, and the relationship between the temperature and the strength in the inspection temperature range is obtained. 2 and 3 are diagrams showing an example of the relationship between the temperature and strength of FRP standard test pieces (standard products) and defective products in the inspection temperature range. FIG. 2 is a diagram of a standard product and an FRP (resin defective product) with reduced resin characteristics, and FIG. 3 is a diagram of a standard product and an FRP (structurally defective product) having a defective fiber structure. The relationship between the temperature and strength of the standard product is also used as reference data.
　図１～３に示したような、ＦＲＰの標準試験片および不良品についての、積層方向の弾性率と繊維方向の圧縮強度との相関関係、および温度と強度との関係は、データベースとして記憶する。 The correlation between the elastic modulus in the laminating direction and the compressive strength in the fiber direction, and the relationship between the temperature and the strength for the standard specimens and defective products of FRP as shown in FIGS. 1 to 3 are stored as a database. .
　樹脂特性の低下による不良と繊維構造の不良とは、強度と温度の関係を調べることにより判別することができる。 Defective due to deterioration of resin characteristics and defective fiber structure can be discriminated by examining the relationship between strength and temperature.
　初めに、樹脂特性の低下により強度が低下した場合を判別する方法について示す。図２は、ＦＲＰの標準品と樹脂不良品について、温度と強度との関係を模式的に示した図である。ＦＲＰの標準品は、樹脂の特性により定まるガラス転移温度（Ｔｇ）以下の温度では、ほぼ一定の強度を示す。強度は、温度が上がりガラス転移温度付近になると低下し始め、さらに温度が上がると著しく低下する。従って、樹脂のガラス転移温度は、製品の使用温度範囲より高くする必要がある。 First, a method for discriminating a case where the strength is reduced due to a decrease in resin characteristics will be described. FIG. 2 is a diagram schematically showing the relationship between temperature and strength for FRP standard products and defective resin products. The standard product of FRP shows a substantially constant strength at a temperature not higher than the glass transition temperature (Tg) determined by the characteristics of the resin. The strength begins to decrease as the temperature increases and near the glass transition temperature, and decreases significantly as the temperature increases. Therefore, the glass transition temperature of the resin needs to be higher than the use temperature range of the product.
　図２の樹脂不良品についてのグラフで示すように、何らかの要因で樹脂の特性が低下し標準品と同等とならず、ガラス転移温度が低下した場合、そのガラス転移温度付近で強度が低下する。従って、強度が低下した温度を調べて標準品のガラス転移温度と比較することにより、樹脂特性の低下の有無を判別することができる。 As shown in the graph of the defective resin product in FIG. 2, the resin characteristics deteriorate for some reason and are not equal to the standard product, and when the glass transition temperature decreases, the strength decreases near the glass transition temperature. Therefore, by examining the temperature at which the strength has decreased and comparing it with the glass transition temperature of the standard product, it is possible to determine whether or not the resin characteristics have been decreased.
　樹脂特性の低下の原因としては、硬化温度異常や保持時間不足などによる硬化不良や、二液混合の樹脂の場合は主剤と硬化剤の配合不良などが考えられる。樹脂特性の低下が見られた場合、このような原因について見直すことにより、適正な製造条件に改善することができる。 The cause of the deterioration of the resin characteristics may be a curing failure due to abnormal curing temperature or insufficient holding time, or in the case of a resin mixed with two liquids, a blending failure of the main agent and the curing agent. When the deterioration of the resin characteristics is observed, it is possible to improve to appropriate manufacturing conditions by reviewing such causes.
　次に、繊維構造の不良により強度が低下した場合を判別する方法について示す。図３は、ＦＲＰの標準品と構造不良品について、温度と強度との関係を模式的に示した図である。構造不良品は、ガラス転移温度は標準品と同様であるが、各温度において全体的に強度が低くなる傾向を示す。従って、各温度での強度を標準品と比較することにより、繊維構造の不良による強度低下の有無を判別することができる。 Next, a method for discriminating a case where the strength is lowered due to a defective fiber structure will be described. FIG. 3 is a diagram schematically showing the relationship between temperature and strength for FRP standard products and structurally defective products. The structurally defective products have the same glass transition temperature as that of the standard products, but the strength tends to decrease as a whole at each temperature. Therefore, by comparing the strength at each temperature with a standard product, it is possible to determine the presence or absence of strength reduction due to a defective fiber structure.
　このように、まず強度と温度の関係を調べることにより、樹脂特性の低下による不良と繊維構造の不良とを判別することができる。 Thus, first, by examining the relationship between strength and temperature, it is possible to discriminate between a defect due to a decrease in resin characteristics and a defect in the fiber structure.
　次に、繊維構造の不良により強度が低下した場合において、繊維構造の不良の原因を判別する方法について説明する。繊維構造の不良による特性変化には、温度変化による影響はほとんどないため、測定の際に温度調節を実施しなくてもよい。前述したように、繊維構造の不良の原因には、繊維の形状不整と繊維の体積率不足とがある。 Next, a method for determining the cause of the defective fiber structure when the strength is reduced due to the defective fiber structure will be described. The characteristic change due to the defective fiber structure is hardly affected by the temperature change, and therefore it is not necessary to adjust the temperature at the time of measurement. As described above, the causes of the defective fiber structure include irregular shape of the fiber and insufficient volume ratio of the fiber.
　まず、繊維構造の不良の原因が、繊維の形状不整か繊維の体積率不足であるかを判別するために、ＦＲＰ構造物の各部の強度分布を調べる方法について説明する。 First, a method for examining the strength distribution of each part of the FRP structure will be described in order to determine whether the cause of the defective fiber structure is irregular fiber shape or insufficient fiber volume ratio.
　繊維は連続的に配置されているため、強度などの特性は、形状不整がある場合には、形状不整がある部分の周辺で連続的に変化する。従って、ＦＲＰ構造部材の面内の２次元的な強度分布を調べ、強度が連続的に徐々に変化しているか、強度低下部が点在するか（強度が不連続に変化するか）を調べれば、繊維構造の不良の原因が、繊維の形状不整であるか繊維の体積率不足であるかを判別することができる。強度が連続的に変化している場合は、繊維の形状不整であり、強度低下部が点在する（強度が不連続に変化する）場合は、局所的な内部欠陥による繊維の体積率不足であると判別できる。局所的な内部欠陥の原因としては、樹脂量の過大やボイドなどが考えられる。ＦＲＰ構造部材の面内の２次元的な強度分布は、上述したように、ＦＲＰの弾性率を測定することにより、推定することが可能である。 Since the fibers are continuously arranged, characteristics such as strength continuously change around the irregular portion when there is irregular shape. Therefore, the two-dimensional intensity distribution in the plane of the FRP structural member can be examined to determine whether the intensity is continuously changing gradually or whether there are scattered strength reduction parts (whether the intensity changes discontinuously). For example, it is possible to determine whether the cause of the defective fiber structure is irregular fiber shape or insufficient fiber volume ratio. If the strength is continuously changing, the shape of the fiber is irregular, and if the strength drop is scattered (the strength changes discontinuously), the fiber volume ratio is insufficient due to local internal defects. It can be determined that there is. Possible causes of local internal defects include an excessive amount of resin and voids. As described above, the in-plane two-dimensional intensity distribution of the FRP structural member can be estimated by measuring the elastic modulus of the FRP.
　ボイドの大きさは、構造物の寸法や製作条件などにより異なるが、コンマ数ｍｍから数ｍｍ程度である。ボイドが集中して存在するということがない場合、強度低下部は、ボイドの大きさの範囲に限られる。 The size of the void varies depending on the dimensions of the structure and the manufacturing conditions, but is about several millimeters to several millimeters. In the case where the voids are not concentrated, the strength-decreasing portion is limited to the void size range.
　繊維構造の不良の原因が繊維の形状不整の場合、数ｍｍ程度の波長の繊維の形状不整（うねり）が存在すると、繊維シートを積層してＦＲＰ構造物を製作する場合には繊維シートの厚さはおおむね１ｍｍ程度であるので、かなり大きな不整となる。従って、繊維シートの厚さの変化は、目視で十分確認可能である。目視で確認するときには、繊維の形状不整の波長が１０ｍｍ以上のものを対象とすればよい。この場合、一定間隔で測定した連続的な強度の変化から、繊維の形状不整の有無を推定することができる。 If the cause of the fiber structure failure is the irregular shape of the fiber, if there is irregular shape (undulation) of the fiber with a wavelength of several millimeters, the thickness of the fiber sheet is required when the FRP structure is manufactured by laminating the fiber sheets. Since the length is about 1 mm, it becomes a considerably large irregularity. Therefore, the change in the thickness of the fiber sheet can be sufficiently confirmed visually. When visually confirming, a fiber having an irregular fiber shape wavelength of 10 mm or more may be used. In this case, the presence or absence of irregular shape of the fiber can be estimated from the continuous change in strength measured at regular intervals.
　繊維の形状不整の有無を調べるための別な方法として、強化繊維と異なる材料の繊維を、形状不整判別用の繊維として予めＦＲＰの構造部材内に埋め込み、目視により調べる方法について説明する。 As another method for investigating the presence or absence of irregularities in the shape of fibers, a method in which fibers of a material different from reinforcing fibers are embedded in the FRP structural member in advance as shape irregularity determination fibers and examined visually will be described.
　ＦＲＰの強化繊維は、一つの構造部材内には通常一つの材料だけを用いる。これは、複数の材料を用いた場合、弾性率や線膨脹係数が異なるので成形しにくいためや、樹脂の硬化時の温度変化により熱応力が発生する可能性があるためである。しかし、ＦＲＰの強化繊維に複数の材料を用いた場合でも、主要な強化繊維の中に異なる種類の材料（以下、「異種材」と称する）の繊維を埋め込み、異種材の繊維の量を、形状不整を判別するために必要な最小限に抑えれば、このような問題が生じにくい。 FRP reinforcing fibers usually use only one material in one structural member. This is because when a plurality of materials are used, the elastic modulus and the linear expansion coefficient are different, so that molding is difficult, and thermal stress may be generated due to a temperature change when the resin is cured. However, even when a plurality of materials are used for the reinforcing fiber of FRP, fibers of different types of materials (hereinafter referred to as “different materials”) are embedded in the main reinforcing fibers, and the amount of fibers of the different materials is determined. Such a problem is unlikely to occur if the minimum necessary for discriminating the shape irregularity is suppressed.
　従って、形状不整を判定するために必要最小限の量の異種材の繊維をＦＲＰに埋め込んでおき、異種材の繊維を目安にして目視によりＦＲＰの繊維の形状を評価すれば、非破壊で容易に繊維の形状不整の検査ができる。異種材の繊維は、周囲の強化繊維とは性質が異なるので形状の変化の様子も異なり、形状不整（うねり）が生じた場合には、この形状不整を発見することが容易になる。すなわち、異種材の繊維の形状が変化している場合には、ＦＲＰの繊維に形状不整があると容易に判別することができる。このようにして、異種材の繊維を形状不整判別用の繊維として用いることができる。また、異種材の繊維の色を強化繊維の色と異なる色にしてもよい。繊維の色が異なると、外観上で異種材を識別しやすくなり、形状不整の有無がより分かりやすくなる。ＦＲＰの構造部材全体について、異種材のうねりの分布状況を調べれば、強化繊維の形状不整の状況を詳細に評価することができる。 Therefore, it is easy and non-destructive to embed the minimum amount of dissimilar material fibers to determine the shape irregularity in the FRP and visually evaluate the FRP fiber shape using the dissimilar material fibers as a guide. In addition, the fiber shape irregularity can be inspected. Since the fibers of different materials have different properties from the surrounding reinforcing fibers, the state of change in shape is also different. When shape irregularity (swell) occurs, it becomes easy to find this irregular shape. That is, when the shape of the fiber of the dissimilar material is changed, it can be easily determined that the FRP fiber has an irregular shape. In this way, the fibers of different materials can be used as the fibers for determining the irregular shape. Further, the color of the fiber of the different material may be different from the color of the reinforcing fiber. If the color of the fiber is different, it will be easier to identify different materials on the appearance, and it will be easier to see if there is an irregular shape. By examining the distribution of the undulations of different materials for the entire FRP structural member, the state of irregular shape of the reinforcing fibers can be evaluated in detail.
　図４は、異種材の繊維をＦＲＰ構造物内に配置する方法について説明するための模式図である。ＦＲＰ構造物は、ＦＲＰの構造部材３からなり、ＦＲＰの構造部材３には、強化繊維１と異種材の繊維２が含まれる。 FIG. 4 is a schematic diagram for explaining a method of arranging dissimilar material fibers in the FRP structure. The FRP structure includes an FRP structural member 3, and the FRP structural member 3 includes reinforcing fibers 1 and dissimilar fibers 2.
　異種材の繊維２は、強化繊維１を含むＦＲＰの構造部材３内の少なくとも１箇所に予め埋め込んでおけばよい。異種材の繊維２を少なくとも１箇所に埋め込めば、ＦＲＰの構造部材３の全体について、強化繊維１の形状不整を評価することが可能である。形状不整の位置や方向を詳細に調べたい場合には、強度上問題にならない範囲内で異種材の繊維２を増やせば、三次元的な形状不整を評価することも可能になり、より詳細な特性評価ができる。 The dissimilar material fibers 2 may be embedded in at least one place in the FRP structural member 3 including the reinforcing fibers 1 in advance. If the dissimilar material fibers 2 are embedded in at least one place, it is possible to evaluate the irregular shape of the reinforcing fibers 1 for the entire FRP structural member 3. If you want to investigate the position and direction of irregular shapes in detail, if you increase the number of fibers 2 of dissimilar materials within the range where there is no problem in strength, it becomes possible to evaluate three-dimensional irregularities. Characteristic evaluation is possible.
　異種材の繊維２は、強化繊維１と弾性率や線膨脹係数が近い材料であれば、成形が容易になるともに、樹脂の硬化時に発生する熱応力を抑制でき、より望ましい。また、例えば風車翼のような屋外で用いられる構造物の場合には、落雷による被害を防ぐために、絶縁材料を用いることが望ましい。 The dissimilar material fiber 2 is more desirable as long as it is a material having a modulus of elasticity and a linear expansion coefficient close to those of the reinforcing fiber 1 and can be easily molded and can suppress the thermal stress generated when the resin is cured. Further, in the case of a structure used outdoors such as a windmill blade, it is desirable to use an insulating material in order to prevent damage due to lightning.
　次に、繊維構造の不良の原因のうち、繊維の体積率不足があるかどうかを調べるための方法について示す。繊維の体積率不足は、成形時に不要な樹脂を十分に流出させられず樹脂量が過大になることや、空気がＦＲＰ内にボイドとなって残ることなどが原因で起こる。樹脂量の過大が原因の場合には、全体の厚さや幅などの寸法が大きくなるので、これらの寸法を調査し、標準寸法よりも一定値以上大きくなっていれば、樹脂量が過大であると判断できる。また、ボイドが原因の場合は、前述したように、ボイドの大きさはコンマ数ｍｍから数ｍｍ程度であるので、この大きさの強度低下部が点在しているかどうかを調べることにより、判別することができる。 Next, a method for investigating whether or not the fiber volume ratio is insufficient among the causes of defective fiber structure will be described. Insufficient fiber volume ratio is caused by the fact that unnecessary resin cannot be sufficiently discharged at the time of molding, and the amount of resin becomes excessive, or air remains as voids in the FRP. If the amount of the resin is excessive, the overall thickness and width will increase, so if these dimensions are examined and if they are larger than the standard dimensions, the resin amount is excessive. It can be judged. In addition, as described above, when the void is the cause, the size of the void is from several commas to several millimeters, and therefore, it is determined by checking whether or not strength reduction portions of this size are scattered. can do.
　以上述べたような樹脂不良品と構造不良品についても、弾性率と強度の関係についてのデータベースを備えることができる。このデータベースは、後述する評価工程の際に、不良原因の判別に用いることができる。また、これら以外にも予想される不具合を反映させた試験片や、経年的に樹脂の特性が劣化した試験片についても、それらのデータについてのデータベースを備えることで、不良原因の判別に用いることができる。 As for the resin defective products and the structural defective products as described above, a database on the relationship between the elastic modulus and the strength can be provided. This database can be used to determine the cause of a defect in an evaluation process described later. In addition to these, test specimens that reflect anticipated defects, and test specimens whose resin characteristics have deteriorated over time should also be used to determine the cause of defects by providing a database of those data. Can do.
　このように弾性率と強度の関係を用いることにより、強度と温度の関係やＦＲＰ構造物の面内の強度分布を調べ、併せて繊維の不整を調べることにより、ＦＲＰの不良の有無およびその原因を調べることができる。 By using the relationship between the elastic modulus and the strength in this way, the relationship between the strength and temperature and the in-plane strength distribution of the FRP structure are examined, and by checking the irregularity of the fiber, the presence / absence of the defect of FRP and the cause thereof are investigated. Can be examined.
　図５は、本発明によるＦＲＰの評価方法を適用する評価装置の一実施例を示す構成図である。本実施例によるＦＲＰの評価装置は、硬度計１１、温度調節装置１２、演算／判定装置１３、記憶装置１４、および表示装置１５からなり、被検体１０であるＦＲＰを評価する。 FIG. 5 is a block diagram showing an embodiment of an evaluation apparatus to which the FRP evaluation method according to the present invention is applied. The FRP evaluation apparatus according to the present embodiment includes a hardness meter 11, a temperature adjustment device 12, a calculation / determination device 13, a storage device 14, and a display device 15, and evaluates the FRP that is the subject 10.
　硬度計１１は、被検体１０の弾性率を測定する。硬度計１１には、超音波硬度計または超音波探傷器が適している。これは、先端部の接触子を被検体１０の表面に押し当て、その時の接触子の接触半径と押し込み深さとの関係から弾性率を求める装置である。この装置では、被検体１０の弾性変形の範囲で評価できるため、被検体１０に損傷を与えることなく評価をすることができる。 The hardness meter 11 measures the elastic modulus of the subject 10. For the hardness meter 11, an ultrasonic hardness meter or an ultrasonic flaw detector is suitable. This is a device that obtains an elastic modulus from the relationship between the contact radius of the contact at that time and the indentation depth by pressing the contact at the distal end against the surface of the subject 10. In this apparatus, since the evaluation can be performed in the range of elastic deformation of the subject 10, the evaluation can be performed without damaging the subject 10.
　超音波硬度計は、被検体１０の表面付近の限られた範囲のみを測定するため、厚さ方向全体についての評価はできないが、逆に樹脂の特性の影響を受けやすいため、樹脂の温度特性を評価する装置として好適である。 Since the ultrasonic hardness tester measures only a limited range near the surface of the specimen 10, the entire thickness direction cannot be evaluated, but conversely, since it is easily affected by the characteristics of the resin, the temperature characteristics of the resin It is suitable as an apparatus for evaluating
　超音波探傷器は、超音波の入射波と反射波の関係から、被検体１０内の異物や内部欠陥の有無を調べることができる。従って、繊維の状況を調べることにより、形状不整の有無を調べることができる。また、ボイドなどの内部欠陥についての評価や、被検体１０の厚さを測定することによる樹脂量の評価も可能である。従って、繊維の体積率不足の有無を調べることができ、内部欠陥が存在する場合や樹脂量が多い場合には、繊維の体積率不足が起きていると分かる。これらの検査結果をデータベースに記憶したデータと照合し、どの不良があるかを判別することにより、強度低下の原因が推定できる。 The ultrasonic flaw detector can check the presence or absence of foreign matter or internal defects in the subject 10 from the relationship between the incident wave and the reflected wave of the ultrasonic wave. Therefore, the presence or absence of shape irregularities can be examined by examining the condition of the fibers. In addition, evaluation of internal defects such as voids, and evaluation of the amount of resin by measuring the thickness of the subject 10 are also possible. Therefore, it can be checked whether or not the fiber volume ratio is insufficient, and it can be understood that the fiber volume ratio is insufficient when an internal defect exists or the amount of resin is large. By comparing these inspection results with the data stored in the database and determining which defect is present, the cause of the strength reduction can be estimated.
　繊維の形状不整を調べる場合には、温度を変更して測定する必要がないので温度調節装置１２を用いなくてもよい。但し、厚さは温度により測定値が変化する恐れがあるため、温度調節装置１２により温度を測定し、厚さの測定値を補正する必要がある。 When investigating irregularities in the shape of the fiber, it is not necessary to change the temperature and measure, so the temperature adjustment device 12 need not be used. However, since the measured value of the thickness may change depending on the temperature, it is necessary to measure the temperature with the temperature adjusting device 12 and correct the measured value of the thickness.
　なお、ここでは弾性率の測定装置として超音波硬度計と超音波探傷器を例示したが、これ以外にも、アコースティックエミッションを用いる装置などの非破壊で弾性率を測定できる装置を用いてもよい。 In addition, although the ultrasonic hardness meter and the ultrasonic flaw detector were illustrated here as the elastic modulus measuring device, a device capable of measuring the elastic modulus nondestructively such as a device using acoustic emission may be used. .
　温度調節装置１２は、温度計とヒータを備え、被検体１０の温度の測定と調節を行う。温度の測定と調節は、被検体１０の弾性率測定部とその周辺に対して行う。温度調節は、最低限、硬度計１１で測定する範囲（予め定めた検査温度範囲）で行えばよいため、小規模なもので対応できる。 The temperature adjustment device 12 includes a thermometer and a heater, and measures and adjusts the temperature of the subject 10. The measurement and adjustment of the temperature are performed on the elastic modulus measurement unit of the subject 10 and its surroundings. The temperature adjustment may be performed at least in the range measured by the hardness meter 11 (predetermined inspection temperature range), and can be handled with a small scale.
　演算／判定装置１３は、硬度計１１で求めた弾性率と記憶装置１４に保存されたデータベースとを比較し、被検体１０の強度を求める。また、求めた被検体１０の強度とデータベースに記憶されたデータとを比較して、不良の有無および不良原因の推定結果を導出する。また、硬度計１１の測定位置を取得し、ＦＲＰの強度分布を求めることもできる。 The arithmetic / judgment device 13 compares the elastic modulus obtained by the hardness meter 11 with the database stored in the storage device 14 to obtain the strength of the subject 10. Further, the obtained intensity of the subject 10 is compared with the data stored in the database to derive the presence / absence of the defect and the estimation result of the defect cause. Moreover, the measurement position of the hardness meter 11 can be acquired and the intensity distribution of FRP can also be calculated | required.
　記憶装置１４は、被検体１０の弾性率の測定結果から強度を推定し被検体１０の不良の有無および不良原因を推定するためのデータベースを備える。データベースは、標準的な条件で適正に製作した標準試験片、繊維含有率を変えて製作した試験片、および樹脂硬化条件を変えて製作した試験片などについてのデータを蓄積したものである。具体的には、図１～３に示したような、試験片の各温度での弾性率と強度の関係や、試験片の温度と強度との関係や、求めたガラス転移温度のデータを備える。不具合の要因となりうるパラメータ（繊維含有率や樹脂硬化条件など）を変更して製作した試験片のデータベースをも備えることにより、不良原因の推定の精度を向上させることができる。但し、不良原因の推定が不要で、不良の有無の評価のみでよい場合には、標準試験片に対するデータのみを備えたデータベースとしてもよい。また、製造上起こりにくい不良に関するパラメータについては、データを備えなくてもよい。 The storage device 14 includes a database for estimating the strength from the measurement result of the elastic modulus of the subject 10 and estimating the presence or absence of the subject 10 and the cause of the failure. The database stores data on standard test pieces properly manufactured under standard conditions, test pieces manufactured by changing the fiber content, and test pieces manufactured by changing the resin curing conditions. Specifically, as shown in FIGS. 1 to 3, data on the relationship between the elastic modulus and strength at each temperature of the test piece, the relationship between the temperature and strength of the test piece, and the obtained glass transition temperature is provided. . By providing a database of test pieces manufactured by changing parameters (such as fiber content and resin curing conditions) that may cause defects, it is possible to improve the accuracy of estimation of the cause of defects. However, if it is not necessary to estimate the cause of the defect and only the evaluation of the presence / absence of the defect is required, the database may include only data for the standard test piece. Moreover, it is not necessary to provide data on parameters relating to defects that are unlikely to occur in manufacturing.
　表示装置１５は、測定結果や評価結果などを表示する。例えば、測定時の温度、各測定温度での弾性率の値、データベースのデータに基づいて弾性率から求められる強度の値、温度と強度との関係から求められるガラス転移温度、測定結果を標準品のデータと比較して不良の有無を判定した結果、および不良がある場合には推定した不良原因の全て、または、これらの一部を表示することができる。 The display device 15 displays measurement results and evaluation results. For example, the measurement temperature, the value of the elastic modulus at each measurement temperature, the strength value obtained from the elastic modulus based on the data in the database, the glass transition temperature obtained from the relationship between temperature and strength, and the measurement results As a result of determining the presence or absence of a defect in comparison with the data, and if there is a defect, it is possible to display all or some of the estimated causes of the defect.
　次に、上述したＦＲＰの評価装置を用いた評価手順を説明する。以下で述べる評価、判別などの演算は、演算／判定装置１３が実行する。評価は、ＦＲＰ構造物のうち予め定めた検査点に対して、それぞれ行う。以下は、１箇所の検査点についての評価手順を説明するが、ＦＲＰ構造物の全体の評価は、以下の評価手順を全ての検査点について行う。 Next, an evaluation procedure using the above-described FRP evaluation apparatus will be described. The calculation / determination device 13 executes calculations such as evaluation and discrimination described below. The evaluation is performed for each predetermined inspection point in the FRP structure. In the following, the evaluation procedure for one inspection point will be described, but the overall evaluation of the FRP structure is performed for all the inspection points.
　まず、被検体１０であるＦＲＰに対して、硬度計１１を用いて弾性率を測定する。また同時に、被検体１０の温度を、温度調節装置１２が備える温度計により測定する。測定した被検体１０の弾性率を、記憶装置１４に保存したデータベースの弾性率と強度との関係（図１に示したような関係）と照合し、被検体１０の強度を求める。 First, the elastic modulus of the FRP that is the subject 10 is measured using the hardness meter 11. At the same time, the temperature of the subject 10 is measured by a thermometer provided in the temperature control device 12. The measured elastic modulus of the subject 10 is collated with the relationship between the elastic modulus and the strength of the database stored in the storage device 14 (the relationship as shown in FIG. 1) to obtain the strength of the subject 10.
　この弾性率を測定して強度を求める工程を、温度調節装置１２で被検体１０の温度を変化させて、予め定めた検査温度範囲内の各検査温度に対して行う。すなわち、各検査温度で被検体１０の弾性率を測定し、データベースの弾性率と強度との関係に基づいて、測定した弾性率から被検体１０の各検査温度での強度を求める。これにより、被検体１０の温度と強度との関係（図２、３に示したような関係）が求められる。 The step of measuring the elastic modulus and obtaining the strength is performed for each inspection temperature within a predetermined inspection temperature range by changing the temperature of the subject 10 with the temperature control device 12. That is, the elastic modulus of the subject 10 is measured at each inspection temperature, and the strength at each inspection temperature of the subject 10 is obtained from the measured elastic modulus based on the relationship between the elastic modulus and the strength of the database. Thereby, the relationship between the temperature and intensity of the subject 10 (the relationship as shown in FIGS. 2 and 3) is obtained.
　被検体１０の温度と強度との関係から、ガラス転移温度（Ｔｇ）を求める。ガラス転移温度（Ｔｇ）は、強度が大きく低下し始める点として求めるが、例えば、基準温度（室温）の強度に対し、強度が９０％に低下した温度というように定めて求めることができる。また、測定対象（被検体１０）に応じて定めることもできる。 The glass transition temperature (Tg) is obtained from the relationship between the temperature and intensity of the subject 10. The glass transition temperature (Tg) is determined as a point at which the strength starts to greatly decrease. For example, the glass transition temperature (Tg) can be determined and determined as a temperature at which the strength is reduced to 90% with respect to the strength at the reference temperature (room temperature). It can also be determined according to the measurement target (subject 10).
　このようにＦＲＰの強度およびガラス転移温度（Ｔｇ）を求めた後、図６に示す判別フローで検査結果を評価する。図６は、ＦＲＰの不良が、樹脂特性の低下による不良か繊維構造の不良かを判別するためのフロー図の一例である。図６は、１箇所の検査点についてのフロー図である。ＦＲＰ構造物の全体について評価する場合には、各検査点に対して図６のフローに示した手順を実施する。 After obtaining the strength of FRP and the glass transition temperature (Tg) in this way, the test results are evaluated by the discrimination flow shown in FIG. FIG. 6 is an example of a flow chart for determining whether the FRP defect is a defect due to a decrease in resin characteristics or a fiber structure defect. FIG. 6 is a flowchart for one inspection point. When evaluating the entire FRP structure, the procedure shown in the flow of FIG. 6 is performed for each inspection point.
　ステップ６０１では、検査温度範囲内の全ての検査温度で、被検体１０（ＦＲＰ）の強度と標準強度とを比較する。標準強度というのは、標準試験片（標準品）の強度のことであり、前述したように、記憶装置１４が備えるデータベースに記憶されている。全ての検査温度で、ＦＲＰの強度が標準強度以上の場合は、現在の検査点の特性の検査は、合格と判定される。 In step 601, the intensity of the subject 10 (FRP) is compared with the standard intensity at all inspection temperatures within the inspection temperature range. The standard strength is the strength of a standard test piece (standard product), and is stored in a database provided in the storage device 14 as described above. When the strength of FRP is equal to or higher than the standard strength at all inspection temperatures, the inspection of the characteristics of the current inspection point is determined to be acceptable.
　ステップ６０１で合格とならなかった場合は、現在の検査点は強度が低下している（弾性率が低い）ため不良と判定され、ステップ６０２に進む。 If not passed in step 601, the current inspection point is judged to be defective because the strength is low (elastic modulus is low), and the process proceeds to step 602.
　ステップ６０２では、不良の原因を判定するために、ガラス転移温度（Ｔｇ）を評価する。被検体１０のガラス転移温度が標準試験片のガラス転移温度（標準値）より低い場合、樹脂の配合不良（攪拌不良等による不均一分布を含む）や硬化条件不良等による樹脂特性の低下が、不良の主な原因と推定される（ステップ６０３）。標準試験片のガラス転移温度（標準値）は、記憶装置１４が備えるデータベースに記憶されている。 In step 602, the glass transition temperature (Tg) is evaluated in order to determine the cause of the failure. When the glass transition temperature of the specimen 10 is lower than the glass transition temperature (standard value) of the standard test piece, the resin characteristics deteriorate due to poor blending of the resin (including non-uniform distribution due to poor stirring, etc.) or poor curing conditions. Presumed to be the main cause of the failure (step 603). The glass transition temperature (standard value) of the standard test piece is stored in a database provided in the storage device 14.
　一方、ガラス転移温度は標準値と差がなく、検査温度範囲内の全ての検査温度で、被検体１０の強度が標準強度より低い場合は、樹脂特性の低下以外の原因、すなわち繊維構造の不良が原因として考えられる（ステップ６０４）。繊維構造の不良の原因としては、繊維の形状不整と繊維の体積率不足が主に考えられる。 On the other hand, the glass transition temperature is not different from the standard value, and when the strength of the specimen 10 is lower than the standard strength at all the test temperatures within the test temperature range, the cause other than the deterioration of the resin characteristics, that is, the fiber structure is defective. (Step 604). The main causes of the defective fiber structure are the irregular shape of the fiber and the insufficient volume ratio of the fiber.
　繊維構造の不良として最も可能性が高い原因は、樹脂より高い弾性率を持つ繊維の体積率が標準試験片の体積率不足よりも少なくなっているという繊維の体積率不足である。この場合、成型時の圧力不足による成型不良や、真空排気が不十分でボイドが複合材（ＦＲＰ）の中に残っていることなどのために、体積率不足が起きていると考えられる。 The most likely cause of a defective fiber structure is a fiber volume ratio deficiency in which the volume ratio of fibers having a higher elastic modulus than the resin is less than the volume ratio deficiency of the standard specimen. In this case, it is considered that the volume ratio is insufficient due to defective molding due to insufficient pressure during molding or insufficient evacuation and voids remaining in the composite material (FRP).
　そこで、繊維の形状不整と繊維の体積率不足とを判別する測定を、被検体１０の複数の検査点について行い、各検査点の位置と強度の関係を調べる。その結果の強度の分布状況を、記憶装置１４に記憶させたデータベースと比較することにより、強度が繊維不整により連続的に変化しているか、ボイドなどにより不連続に変化しているかを調べる。これらの測定結果および判別結果を表示装置１５に表示し、結果を検討する。これにより、繊維構造の不良の原因を判別することができる。 Therefore, the measurement for discriminating between the irregular shape of the fiber and the insufficient volume ratio of the fiber is performed for a plurality of inspection points of the subject 10, and the relationship between the position and intensity of each inspection point is examined. By comparing the resulting intensity distribution state with a database stored in the storage device 14, it is examined whether the intensity changes continuously due to fiber irregularity or discontinuously due to voids. These measurement results and discrimination results are displayed on the display device 15, and the results are examined. Thereby, the cause of the defective fiber structure can be determined.
　このようにして不良の原因が簡易に判別できるため、製造工程における問題点を明らかにし、いち早く製品の改善に反映することができる。 Since the cause of the defect can be easily identified in this way, problems in the manufacturing process can be clarified and reflected in product improvement as soon as possible.
　図７は、ＦＲＰの不良が、樹脂特性の低下による不良か繊維構造の不良かを判別し、さらに、繊維構造の不良の原因が、繊維の形状不整か繊維の体積率不足かを判別するためのフロー図の一例である。例えば、硬度計１１として超音波探傷器を用い、ＦＲＰの繊維の形状不整やボイドの有無を求めた後、図７に示す判別フローで試験結果を評価する。図７は、図６と同様に、１箇所の検査点についてのフロー図であり、ＦＲＰ構造物の全体については、各検査点に対して図７のフローに示した手順を実施する。 FIG. 7 is for determining whether the defect of FRP is a defect due to the deterioration of the resin characteristics or the defect of the fiber structure, and further, determining whether the cause of the defect of the fiber structure is an irregular shape of the fiber or an insufficient volume ratio of the fiber. It is an example of the flowchart of this. For example, an ultrasonic flaw detector is used as the hardness meter 11, and after determining the irregularity of the FRP fiber shape and the presence or absence of voids, the test results are evaluated by the discrimination flow shown in FIG. FIG. 7 is a flowchart for one inspection point, as in FIG. 6. For the entire FRP structure, the procedure shown in the flow of FIG. 7 is performed for each inspection point.
　まず、硬度計１１として超音波硬度計を用い、ステップ７０１からステップ７０３までの処理を実施する。ステップ７０１からステップ７０３までの処理は、図６に示したステップ６０１からステップ６０３までの処理に対応し、それぞれステップ６０１からステップ６０３と同様の処理を行う。 First, an ultrasonic hardness tester is used as the hardness tester 11, and the processing from step 701 to step 703 is performed. The processing from Step 701 to Step 703 corresponds to the processing from Step 601 to Step 603 shown in FIG. 6, and the same processing as Step 601 to Step 603 is performed.
　ステップ７０３で、ガラス転移温度は標準値と差がなく、被検体１０の強度が標準強度より低い場合は、樹脂特性の低下以外の原因、すなわち繊維構造の不良が原因として考えられるので、ステップ７０４に進む。 In step 703, if the glass transition temperature is not different from the standard value and the strength of the specimen 10 is lower than the standard strength, it can be considered as a cause other than the deterioration of the resin properties, that is, the defect of the fiber structure. Proceed to
　ステップ７０４では、繊維の形状不整（うねり）がある場合は、ＦＲＰの強度低下は、繊維の形状不整が原因であると判別する（ステップ７０５）。繊維の形状不整の有無は、先に述べた、繊維の形状不整の有無を調べるための方法によって求めることができる。 In step 704, if there is irregularity (swell) in the fiber, it is determined that the decrease in the strength of the FRP is caused by irregularity in the fiber (step 705). The presence / absence of the irregular shape of the fiber can be determined by the method for examining the presence / absence of the irregular shape of the fiber described above.
　繊維の形状不整（うねり）がない場合は、ＦＲＰの強度低下は、繊維の体積率不足が原因であると判別する（ステップ７０６）。繊維の体積率不足は、強度がボイドなどにより不連続に変化しているかを調べることによっても判別できる。 If there is no irregularity (swell) in the shape of the fiber, it is determined that the decrease in the strength of the FRP is caused by a shortage of the fiber volume ratio (step 706). Insufficient fiber volume fraction can also be determined by examining whether the strength changes discontinuously due to voids or the like.
　以上のように、樹脂特性の低下、繊維の形状不整、または繊維の体積率不足を評価することにより、ＦＲＰの不良（強度低下）の原因を判定することができる。従って、本発明によるＦＲＰの評価方法および評価装置を用いると、ＦＲＰの強度低下の有無とその原因を容易に求めることができ、高い信頼性を持つＦＲＰ構造物を製作できる。 As described above, the cause of FRP failure (strength reduction) can be determined by evaluating the deterioration of the resin characteristics, the irregular shape of the fiber, or the insufficient volume ratio of the fiber. Therefore, by using the FRP evaluation method and evaluation apparatus according to the present invention, it is possible to easily determine whether or not the strength of the FRP is reduced and the cause thereof, and to manufacture a highly reliable FRP structure.
　以上で説明した評価方法は、主にＦＲＰ構造物の初期特性を評価するのに用いられる方法である。本発明は、ＦＲＰ構造物の特性の経時変化を評価するのに用いることもできる。 The evaluation method described above is a method mainly used for evaluating the initial characteristics of the FRP structure. The present invention can also be used to evaluate changes over time in the properties of FRP structures.
　ＦＲＰの樹脂は、長年の運転により経年劣化が生じ、強度が低下する傾向を示す。また、繰り返し荷重を受ける部材に用いられる場合には、疲労による強度低下が生じる。これらの強度低下は、それぞれが別々に生じる場合もあり、重畳して生じる場合もある。従って、ＦＲＰ構造物の中で強度低下が最も顕著に生じる部分について、経過時間または繰り返し回数に伴う強度の変化を定期的に測定することにより、ＦＲＰ構造物の余寿命を評価することができる。 FRP resin tends to deteriorate over time due to long-term operation, and the strength tends to decrease. Moreover, when it is used for a member that receives repeated loads, the strength is reduced due to fatigue. These strength reductions may occur separately or may overlap. Therefore, the remaining life of the FRP structure can be evaluated by periodically measuring the change in strength with the elapsed time or the number of repetitions of the portion where the strength is most significantly reduced in the FRP structure.
　図８は、ＦＲＰ構造物の経過時間による強度の変化例を示す図である。図８に示したように、強度は経過時間とともに低下する。 FIG. 8 is a diagram showing an example of a change in strength due to the elapsed time of the FRP structure. As shown in FIG. 8, the intensity decreases with the elapsed time.
　図９は、ＦＲＰ構造物に一定負荷を繰り返しかけた場合の、繰り返し回数と強度の関係の例を示す図である。標準品（標準試験片）と構造不良品（繊維構造が不良であるＦＲＰ）とについて示したが、繰り返し回数の増加に対する強度低下は、構造不良品のほうが標準品よりも大きい。 FIG. 9 is a diagram showing an example of the relationship between the number of repetitions and the strength when a constant load is repeatedly applied to the FRP structure. A standard product (standard test piece) and a structurally defective product (FRP having a defective fiber structure) are shown. However, the structurally defective product has a greater decrease in strength with respect to the increase in the number of repetitions than the standard product.
　ＦＲＰの強度は、繊維の角度により変化が異なり、特に繊維の形状不整（うねり）がある構造不良部分で低下率が高くなる。これは、形状不整（うねり）によりひずみが集中する部分ができ、疲労特性は応力の局所的な集中により変化するため、形状不整の部分での疲労による強度低下が顕著になりやすいからである。従って、生じた形状不整が初期の評価で許容できる程度だとしても、経年的な変化は形状不整のない部分よりも顕著になる場合があるので、形状不整が生じた部分に対しては、重点的に定期的な評価を実施することが必要となる。 The strength of FRP varies depending on the angle of the fiber, and the rate of decrease is particularly high in a defective part where the fiber has irregular shape (swells). This is because a strain is concentrated due to shape irregularity (swell), and the fatigue characteristics change due to local concentration of stress, so that a decrease in strength due to fatigue tends to be remarkable at the irregular shape. Therefore, even if the resulting shape irregularity is acceptable in the initial evaluation, the secular change may be more noticeable than the portion without shape irregularity. Periodic evaluations are necessary.
　図１０は、ＦＲＰ構造物の検査範囲内の各検査点について、上述した評価方法を実施するための構成の一例を説明する図である。図１０の上図は側面図であり、下図は上面図である。一例として、被検体１０は、上面形状が長方形であるとしている。 FIG. 10 is a diagram illustrating an example of a configuration for performing the above-described evaluation method for each inspection point within the inspection range of the FRP structure. The upper view of FIG. 10 is a side view, and the lower view is a top view. As an example, it is assumed that the subject 10 has a rectangular top surface shape.
　本評価装置のうち硬度計１１を備える部分を被検体１０の長手方向（図１０の左右方向）に移動させながら、被検体１０の特性（弾性率）を測定していく。本評価装置は、硬度計１１を被検体１０の幅方向（図１０の下図の上下方向）について動かす機構を備えており、被検体１０の幅方向についても特性を測定することができる。従って、硬度計１１は、被検体１０の面上を２次元的に走査し、特性を測定することができる。 The characteristic (elastic modulus) of the subject 10 is measured while moving the portion having the hardness meter 11 in the evaluation apparatus in the longitudinal direction of the subject 10 (left-right direction in FIG. 10). The evaluation apparatus includes a mechanism for moving the hardness meter 11 in the width direction of the subject 10 (the vertical direction in the lower diagram of FIG. 10), and can measure the characteristics in the width direction of the subject 10. Therefore, the hardness meter 11 can scan the surface of the subject 10 two-dimensionally and measure the characteristics.
　このようにして、本評価装置は、被検体１０の面上の各検査点での特性を測定する。その際に、検査点の位置座標、温度ごとの弾性率、繊維方向、ボイドの有無、板厚等の複数の測定データを記憶装置１４（図５を参照、図１０では図示せず）に記憶させる。測定データを演算／判定装置１３（図５を参照、図１０では図示せず）で演算して結果を評価し、不良の有無およびその位置を求める。 In this way, the evaluation apparatus measures the characteristics at each inspection point on the surface of the subject 10. At that time, the storage device 14 (see FIG. 5, not shown in FIG. 10) stores a plurality of measurement data such as the position coordinates of the inspection point, the elastic modulus at each temperature, the fiber direction, the presence or absence of voids, and the plate thickness. Let The measurement data is calculated by the calculation / judgment device 13 (see FIG. 5, not shown in FIG. 10), and the result is evaluated to determine the presence / absence of a defect and its position.
　図１０では、ＦＲＰ構造物（被検体１０）の上面形状が長方形であり、硬度計１１を直交する２軸方向に走査させる機構を持つ評価装置を示したが、本評価装置は、この例に限らず、ＦＲＰ構造物の形状に適した走査機構を持つことができる。例えば、ＦＲＰ構造物が球状であれば、その球面に沿って走査する機構を持つことができる。 FIG. 10 shows an evaluation apparatus having a mechanism in which the upper surface shape of the FRP structure (subject 10) is rectangular and the hardness meter 11 is scanned in two orthogonal directions, but this evaluation apparatus is shown in this example. Not limited to this, a scanning mechanism suitable for the shape of the FRP structure can be provided. For example, if the FRP structure is spherical, it can have a mechanism for scanning along the spherical surface.
　これまでは、一方向強化ＦＲＰに対して本発明を適用した例について説明したが、これ以外の強化構造を持つＦＲＰに対しても、本発明は適用可能である。特に、積層構造を持つＦＲＰには好適である。 So far, the example in which the present invention is applied to the unidirectional reinforced FRP has been described. However, the present invention can also be applied to FRPs having other reinforced structures. In particular, it is suitable for FRP having a laminated structure.
　１…強化繊維、２…異種材の繊維、３…ＦＲＰの構造部材、１０…被検体、１１…硬度計、１２…温度調節装置、１３…演算／判定装置、１４…記憶装置、１５…表示装置。 DESCRIPTION OF SYMBOLS 1 ... Reinforcement fiber, 2 ... Dissimilar material fiber, 3 ... FRP structural member, 10 ... Test object, 11 ... Hardness meter, 12 ... Temperature control device, 13 ... Calculation / determination device, 14 ... Memory | storage device, 15 ... Display apparatus.

Claims (12)

  1. 　被検体であるＦＲＰの弾性率を少なくとも一つの検査温度について測定し、
    　測定した前記ＦＲＰの弾性率を予め求めておいた参照用の弾性率と圧縮強度との関係と照合して前記ＦＲＰの圧縮強度を求めて、前記ＦＲＰの温度と圧縮強度との関係を求め、　求めた前記ＦＲＰの温度と圧縮強度との関係と、予め求めておいた参照用の温度と圧縮強度との関係を比較して、前記ＦＲＰの強度低下およびその原因の少なくとも一つを判別する、
    ことを特徴とするＦＲＰの評価方法。     Measure the elastic modulus of the subject FRP for at least one test temperature;
    The elastic modulus of the measured FRP is compared with the relationship between the elastic modulus for reference and the compression strength obtained in advance to obtain the compression strength of the FRP, and the relationship between the temperature of the FRP and the compression strength is obtained. Comparing the relationship between the calculated temperature and compressive strength of the FRP and the relationship between the reference temperature and compressive strength determined in advance to determine at least one of the strength decrease of the FRP and its cause;
    FRP evaluation method characterized by the above.
  2. 　請求項１記載のＦＲＰの評価方法において、
    　前記ＦＲＰの弾性率を複数の検査温度について測定し、
    　測定した前記ＦＲＰの各弾性率を前記参照用の弾性率と圧縮強度との関係と照合して、前記複数の検査温度での前記圧縮強度を求め、
    　前記複数の検査温度とこれらの検査温度での前記圧縮強度との関係から、前記ＦＲＰのガラス転移温度を求め、
    　求めた前記ガラス転移温度が前記参照用の温度と圧縮強度との関係から求まるガラス転移温度より低い場合には、前記ＦＲＰの強度低下の原因は、前記ＦＲＰの樹脂特性の低下であると判別するＦＲＰの評価方法。     The FRP evaluation method according to claim 1,
    Measuring the elastic modulus of the FRP for a plurality of inspection temperatures;
    Each elastic modulus of the measured FRP is compared with the relationship between the elastic modulus for reference and the compressive strength, and the compressive strength at the plurality of inspection temperatures is obtained,
    From the relationship between the plurality of inspection temperatures and the compressive strength at these inspection temperatures, the glass transition temperature of the FRP is determined,
    When the obtained glass transition temperature is lower than the glass transition temperature obtained from the relationship between the reference temperature and the compressive strength, it is determined that the cause of the decrease in the strength of the FRP is a decrease in the resin properties of the FRP. Evaluation method of FRP.
  3. 　請求項１記載のＦＲＰの評価方法において、
    　前記ＦＲＰの弾性率を複数の検査温度について測定し、
    　測定した前記ＦＲＰの各弾性率を前記参照用の弾性率と圧縮強度との関係と照合して、前記複数の検査温度での前記圧縮強度を求め、
    　前記複数の検査温度とこれらの検査温度での前記圧縮強度との関係と、前記参照用の温度と圧縮強度との関係とを比較し、
    　前記複数の検査温度の全てで、前記ＦＲＰの圧縮強度が前記参照用の圧縮強度より低い場合には、前記ＦＲＰの強度低下の原因は、前記ＦＲＰの繊維構造の不良であると判別するＦＲＰの評価方法。     The FRP evaluation method according to claim 1,
    Measuring the elastic modulus of the FRP for a plurality of inspection temperatures;
    Each elastic modulus of the measured FRP is compared with the relationship between the elastic modulus for reference and the compressive strength, and the compressive strength at the plurality of inspection temperatures is obtained,
    Comparing the relationship between the plurality of inspection temperatures and the compressive strength at these inspection temperatures with the relationship between the reference temperature and compressive strength;
    When the compressive strength of the FRP is lower than the compressive strength for reference at all of the plurality of inspection temperatures, it is determined that the cause of the decrease in the strength of the FRP is a defect in the fiber structure of the FRP. Evaluation methods.
  4. 　請求項３記載のＦＲＰの評価方法において、
    　前記ＦＲＰの弾性率を複数の位置で測定し、前記複数の位置それぞれでの前記ＦＲＰの圧縮強度を求めて、前記ＦＲＰの圧縮強度分布を求め、
    　前記圧縮強度が連続的に変化している場合には、前記繊維構造の不良の原因は、前記ＦＲＰの繊維の形状不整であり、
    　前記圧縮強度が不連続に変化している場合には、前記繊維構造の不良の原因は、前記ＦＲＰの繊維の体積率不足であると判別するＦＲＰの評価方法。     In the FRP evaluation method according to claim 3,
    Measure the elastic modulus of the FRP at a plurality of positions, determine the compressive strength of the FRP at each of the plurality of positions, determine the compressive strength distribution of the FRP,
    When the compressive strength is continuously changing, the cause of the defective fiber structure is an irregular shape of the fiber of the FRP,
    When the compressive strength changes discontinuously, the FRP evaluation method determines that the cause of the defective fiber structure is an insufficient volume ratio of the FRP fibers.
  5. 　請求項１から３のいずれか１項記載のＦＲＰの評価方法において、
    　前記ＦＲＰに、前記ＦＲＰの強化繊維とは異なる種類の繊維を予め埋め込んでおき、
    　前記異なる種類の繊維の形状が変化している場合には、前記ＦＲＰの強度低下の原因は、前記ＦＲＰの繊維の形状不整であると判別するＦＲＰの評価方法。     In the FRP evaluation method according to any one of claims 1 to 3,
    In the FRP, a fiber of a type different from the reinforcing fiber of the FRP is embedded in advance,
    An FRP evaluation method for determining that the cause of a decrease in strength of the FRP is an irregular shape of the fiber of the FRP when the shapes of the different types of fibers are changing.
  6. 　請求項５記載のＦＲＰの評価方法において、
    　前記異なる種類の繊維の色は、前記ＦＲＰの強化繊維の色と異なるＦＲＰの評価方法。     In the FRP evaluation method according to claim 5,
    The color of the different types of fibers is an FRP evaluation method that is different from the color of the FRP reinforcing fibers.
  7. 　請求項１から３のいずれか１項記載のＦＲＰの評価方法において、
    　前記ＦＲＰの内部欠陥の有無を測定し、
    　前記内部欠陥が存在する場合には、前記ＦＲＰの強度低下の原因は、前記ＦＲＰの繊維の体積率不足であると判別するＦＲＰの評価方法。     In the FRP evaluation method according to any one of claims 1 to 3,
    Measure the presence or absence of internal defects in the FRP,
    The FRP evaluation method for determining that the cause of the decrease in the strength of the FRP is an insufficient volume ratio of the fiber of the FRP when the internal defect exists.
  8. 　被検体であるＦＲＰの弾性率を測定する装置と、
    　前記ＦＲＰの弾性率測定部の温度を調節する温度調節装置と、
    　予め求めた弾性率と圧縮強度との関係を示す第１の参照用データと、予め求めた温度と圧縮強度との関係とを示す第２の参照用データとを記憶する記憶装置と、
    　少なくとも一つの検査温度について測定した前記ＦＲＰの弾性率を第１の参照用データと照合して前記ＦＲＰの温度と圧縮強度との関係を求め、さらに、求めた前記ＦＲＰの温度と圧縮強度との関係と第２の参照用データとを比較して、前記ＦＲＰの強度低下およびその原因の少なくとも一つを判別する演算装置と、
    を備えることを特徴とするＦＲＰの評価装置。     A device for measuring the elastic modulus of the FRP as a subject;
    A temperature adjusting device for adjusting the temperature of the elastic modulus measuring section of the FRP;
    A storage device for storing first reference data indicating a relationship between a predetermined elastic modulus and compressive strength, and second reference data indicating a relationship between a predetermined temperature and compressive strength;
    The elastic modulus of the FRP measured for at least one inspection temperature is collated with the first reference data to determine the relationship between the FRP temperature and the compressive strength, and the calculated FRP temperature and compressive strength An arithmetic device that compares the relationship with the second reference data to determine at least one of the FRP strength decrease and the cause thereof;
    An FRP evaluation apparatus comprising:
  9. 　請求項８記載のＦＲＰの評価装置において、
    　前記弾性率を測定する装置は、前記ＦＲＰの弾性率を複数の検査温度について測定し、　前記演算装置は、測定した前記ＦＲＰの各弾性率を前記第１の参照用データと照合して、前記複数の検査温度での前記圧縮強度を求め、
    前記複数の検査温度とこれらの検査温度での前記圧縮強度との関係から、前記ＦＲＰのガラス転移温度を求め、
    求めた前記ガラス転移温度が前記第２の参照用データから求まるガラス転移温度より低い場合には、前記ＦＲＰの強度低下の原因は、前記ＦＲＰの樹脂特性の低下であると判別するＦＲＰの評価装置。     In the FRP evaluation apparatus according to claim 8,
    The apparatus for measuring the elastic modulus measures the elastic modulus of the FRP for a plurality of inspection temperatures, and the arithmetic device collates the measured elastic modulus of the FRP with the first reference data, and Obtaining the compressive strength at a plurality of inspection temperatures;
    From the relationship between the plurality of inspection temperatures and the compressive strength at these inspection temperatures, the glass transition temperature of the FRP is determined,
    An FRP evaluation apparatus that determines that the cause of the decrease in the strength of the FRP is a decrease in the resin properties of the FRP when the determined glass transition temperature is lower than the glass transition temperature determined from the second reference data .
  10. 　請求項８記載のＦＲＰの評価装置において、
    　前記弾性率を測定する装置は、前記ＦＲＰの弾性率を複数の検査温度について測定し、　前記演算装置は、測定した前記ＦＲＰの各弾性率を前記第１の参照用データと照合して、前記複数の検査温度での前記圧縮強度を求め、
    前記複数の検査温度とこれらの検査温度での前記圧縮強度との関係と、前記第２の参照用データとを比較し、
    前記複数の検査温度の全てで、前記ＦＲＰの圧縮強度が前記第２の参照用データの圧縮強度より低い場合には、前記ＦＲＰの強度低下の原因は、前記ＦＲＰの繊維構造の不良であると判別するＦＲＰの評価装置。     In the FRP evaluation apparatus according to claim 8,
    The apparatus for measuring the elastic modulus measures the elastic modulus of the FRP for a plurality of inspection temperatures, and the arithmetic device collates the measured elastic modulus of the FRP with the first reference data, and Obtaining the compressive strength at a plurality of inspection temperatures;
    Comparing the relationship between the plurality of inspection temperatures and the compressive strength at these inspection temperatures with the second reference data;
    When the compressive strength of the FRP is lower than the compressive strength of the second reference data at all of the plurality of inspection temperatures, the cause of the decrease in the strength of the FRP is a defective fiber structure of the FRP. FRP evaluation device for discrimination.
  11. 　請求項１０記載のＦＲＰの評価装置において、
    　前記弾性率を測定する装置は、前記ＦＲＰの弾性率を複数の位置で測定し、
    　前記演算装置は、前記ＦＲＰの弾性率の測定位置を取得し、前記複数の位置それぞれでの前記ＦＲＰの圧縮強度を求めて、前記ＦＲＰの圧縮強度分布を求め、
    前記圧縮強度が連続的に変化している場合には、前記繊維構造の不良の原因は、前記ＦＲＰの繊維の形状不整であり、
    前記圧縮強度が不連続に変化している場合には、前記繊維構造の不良の原因は、前記ＦＲＰの繊維の体積率不足であると判別するＦＲＰの評価装置。     In the FRP evaluation apparatus according to claim 10,
    The apparatus for measuring the elastic modulus measures the elastic modulus of the FRP at a plurality of positions,
    The arithmetic device acquires the measurement position of the elastic modulus of the FRP, obtains the compression strength of the FRP at each of the plurality of positions, obtains the compression strength distribution of the FRP,
    When the compressive strength is continuously changing, the cause of the defective fiber structure is an irregular shape of the fiber of the FRP,
    When the compressive strength changes discontinuously, the FRP evaluation apparatus determines that the cause of the defect in the fiber structure is an insufficient volume ratio of the fibers of the FRP.
  12. 　請求項８から１０のいずれか１項記載のＦＲＰの評価装置において、
    　前記ＦＲＰの内部欠陥の有無を測定する装置を備え、
    　前記演算装置は、前記内部欠陥が存在する場合には、前記ＦＲＰの強度低下の原因は、前記ＦＲＰの繊維の体積率不足であると判別するＦＲＰの評価装置。     In the FRP evaluation apparatus according to any one of claims 8 to 10,
    A device for measuring the presence or absence of internal defects in the FRP;
    The calculation device is an FRP evaluation device that determines that the cause of the decrease in the strength of the FRP is an insufficient volume ratio of the fibers of the FRP when the internal defect exists.
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