JP5050699B2 - Molding status monitoring method for fiber reinforced plastic - Google Patents

Description

  The present invention relates to a method for monitoring the molding condition of fiber reinforced plastic, in particular, the impregnation condition of a liquid material, and more particularly relates to a method effective for monitoring the impregnation condition of a matrix resin to a reinforcing fiber substrate used for FRP molding.

  Carbon fiber reinforced plastic (hereinafter referred to as CFRP) using carbon fiber or glass fiber as reinforced fiber, fiber reinforced plastic (hereinafter referred to as FRP) represented by glass fiber reinforced plastic (hereinafter referred to as GFRP) is lightweight and has high durability. Since it has, it is applied as various structural members, such as a motor vehicle and an aircraft.

  As a typical method for producing these FRPs, an autoclave molding method using a prepreg is known. In such a molding method, an intermediate base material called a prepreg in which a reinforcing fiber is impregnated with a matrix resin in advance is stacked on a mold, and then vacuum-sealed with a film material and heated and pressurized in an autoclave to form a composite material. . However, since the matrix resin impregnated in the prepreg is a thermosetting resin containing a curing agent, the curing reaction gradually proceeds, so that the pot life is short and a freezing storage facility is required. The restrictions on use were great.

  Therefore, in recent years, the RTM molding method has attracted attention as a method that can be molded more easily than the conventional autoclave molding using a prepreg. The Resin Transfer Molding (hereinafter referred to as RTM) molding method is a method in which a reinforcing fiber base (a laminate of reinforcing fiber sheets that have been pre-shaped) is placed in a mold, a matrix resin is injected, and then cured. In this RTM molding method, the resin and the curing agent may be mixed immediately before the injection of the matrix resin, and the matrix resin can be divided into the resin and the curing agent and stored at room temperature, so a large-scale freezing storage facility is unnecessary. . In addition, there is an advantage that large equipment such as an autoclave is not required at the time of molding.

  However, if the molding die is opaque due to metal or the like when the matrix resin is injected, the impregnation state of the resin cannot be grasped visually. Further, even when a transparent mold such as a film bag material used in vacuum RTM is used, when the reinforcing fiber base is made of carbon fiber, the impregnation state of the resin cannot be grasped visually. As a result, even if a part of the reinforcing fiber base material is difficult to be impregnated with the resin and non-impregnation occurs, this cannot be confirmed until the resin is completely cured and demolded. There is a problem that it is impossible to prevent the entire product from being wasted due to non-impregnation. In addition, in the above case, the thickness of the molded body impregnated with the resin cannot be grasped visually, etc., and as a result, even if the thickness is different from the design value, until the resin is cured and demolded Since this cannot be confirmed, there is also a problem that it is impossible to prevent the entire product from being wasted due to some thickness defects. In particular, in the molding in which a large amount of material is used and impregnation is performed over a long time, such as in the case of aircraft wing molding, the manufacturing loss due to non-impregnation or thickness failure is large.

  As a method of monitoring the state of impregnation of the liquid material into the reinforcing fiber base during molding, an optical fiber is placed in the mold together with the reinforcing fiber base, and when the liquid reaches the tip of the optical fiber, the incident light is reflected on the resin surface. Thus, a method of monitoring the arrival of the liquid material by configuring it to return to the light receiving end is known (Patent Document 1). This method is devised to minimize the influence on the flow of the liquid material by arranging an optical fiber along the reinforcing fiber unlike a normal embedded resin-impregnated sensor. After the liquid is cured, the optical fiber remains on the reinforcing fiber substrate, so that the impregnation behavior during molding can be monitored, but it is necessary to sacrifice one actual size molded body to determine the molding conditions. .

  Another method for monitoring the liquid impregnation status during molding is to provide a partition wall between the reinforcing fiber substrate and the sensor and measure the sound wave reflected from the contact surface between the partition wall and the reinforcing fiber substrate. A method for monitoring the behavior of a liquid on the contact surface is known (Patent Document 2). This method monitors the behavior of the resin on the surface of the reinforcing fiber substrate. By applying this method, the impregnation behavior during molding can be monitored without sacrificing the molded body.

However, the monitoring range is wide enough to guarantee the impregnation of the liquid material in the thickness direction of the reinforcing fiber without eroding the product due to residual sensor, not only the dynamic impregnation status during molding can be monitored, but also the thickness monitoring There was no low-cost technology that could be done.
JP 2001-27678 A JP 2006-103190 A

  When molding is performed by monitoring the impregnation behavior during molding by the conventional method, it is not impregnated when the cross section of the molded body is observed after molding, even though it is confirmed that the resin has spread during molding. May remain.

  The object of the present invention is to solve such problems, that is, in FRP molding, by monitoring the impregnation state of the liquid material during molding at low cost and obtaining a good molded product in which no unimpregnated part remains. is there.

  In addition, when molding is performed by monitoring the impregnation behavior during molding by a conventional method, the molded article after molding is confirmed even though it is confirmed that the thickness of the reinforcing fiber base is as designed. When the thickness of the resin is measured, the thickness may not be as designed due to the influence of the temperature distribution in the oven used for curing the resin. Another object of the present invention is to solve such problems, and in FRP molding, both the impregnation state of the liquid material during molding and the thickness of the molded product are monitored at low cost, and no unimpregnated portion remains. And, it is to obtain a good molded body having a thickness as designed.

  The present inventors examined the cause of the unimpregnated portion remaining in the molded body formed by applying the conventional monitoring method. These are all resins between the reinforcing fiber and the mold or between the reinforcing fibers. Based on the idea that the impregnation was monitored, a method that could confirm the unimpregnated portion in the fiber bundle was examined.

  Usually, a mixture of a liquid and a solid such as a reinforcing fiber scatters sound waves due to non-uniform acoustic impedance, and its propagation is difficult, and the liquid propagates sound waves to the reinforcing fiber substrate being impregnated. No attempt was made to monitor the impregnation of the liquid material. In order to increase the propagation capability of sound waves, it is generally known that the center frequency of a sound wave sensor that transmits and receives sound waves is lowered and driven at a low frequency according to this. However, if the center frequency is lowered too much, inspections using pulse waveforms that can provide important information such as the thickness and flatness of the measurement object can be performed without making the body of the pulse waveform because the time width of the oscillating pulse wave becomes longer. become unable.

  The present inventors have intensively studied a center frequency that can use a pulse waveform and can pass through a reinforcing fiber base of 50 ply or more, for example, 52 ply, and when a specific sound wave is used, the liquid material impregnated reinforcement The present inventors have found that sound waves can be efficiently propagated to the fiber base material, and have reached the present invention.

In order to achieve the above-described object, the present invention has one of the following configurations.
(1) In the process of impregnating the liquid material into the reinforcing fiber base having a plate-like portion arranged in the mold, a pulsed sound wave is transmitted from the first surface side of the reinforcing fiber base, and the reinforcing fiber base The sound wave is received on the second surface side of the material, and the impregnation state of the liquid material is detected by a change in the received sound wave intensity, and the thickness of the reinforcing fiber base impregnated with the liquid material from the propagation time of the received sound wave A method for monitoring the molding status of a fiber reinforced plastic, characterized by measuring the thickness.
( 2 ) Utilizing the fact that the sound intensity increases from the value obtained when the liquid is not impregnated as the impregnation of the liquid progresses and finally becomes a constant value, The method for monitoring the molding status of the fiber-reinforced plastic according to (1) , wherein the impregnation status is detected.
( 3 ) The sound wave intensity is measured at a plurality of positions in the impregnation direction of the liquid material, and the maximum value of the sound wave intensity is obtained from the change in the sound wave intensity at the upstream position. The method for monitoring the molding status of the fiber-reinforced plastic according to ( 2 ), wherein the reaching of the value is determined.
( 4 ) The fiber reinforced plastic molding condition monitoring method according to any one of (1) to ( 3 ), wherein the pulse has a time width of 0.83 to 1.25 μsec.
( 5 ) A method for producing a fiber reinforced plastic in which a reinforced fiber base material is impregnated with a liquid resin, wherein the resin impregnation status is detected by the molding status monitoring method according to any one of (1) to ( 4 ). And a method for producing a fiber reinforced plastic, wherein the impregnation step is controlled.

  According to the present invention, it is possible to easily and reliably monitor the impregnation state of the liquid material. When producing the FRP structure using the monitoring method of the present invention, it is possible to easily and reliably monitor that the liquid material impregnated in the reinforcing fiber base material is completely impregnated to a predetermined position. Therefore, it becomes easy to improve the production yield and quality of the resin impregnation step in the production of the FRP structure, and more reliably satisfy the product approval standards. Furthermore, it is possible to automate the process and reduce manpower.

In particular, according to the above-described invention of ( 1 ), in addition to the above-described effects, the detection of the impregnation state of the liquid material and the measurement of the thickness can be carried out at a low cost using the same apparatus if necessary. Therefore, it is possible to correlate the production conditions that could not be accurately known in the past with the resin impregnation situation and the thickness change of the reinforcing fiber base, and by selecting the optimum production conditions, the unimpregnated part does not remain, and In addition, it is possible to obtain an effect that a good FRP molded product having a thickness as designed can be obtained.

  The present invention relates to the state of impregnation of the liquid material into the plate-like reinforcing fiber base material, preferably the state of impregnation and the thickness over time in the process of impregnating the plate-like reinforcing fiber base material placed in the mold. On how to monitor.

  As long as the mold in the present invention is a mold that forms a closed space (molding cavity), it may be a combination of a plurality of molds used in normal RTM molding to form a closed space (molding cavity), A molding die made of a film material in which a reinforcing fiber base material is disposed on the lower die and a closed space (molding cavity) is formed by a sealing material and a film may be used. The present invention is applied to a step of impregnating a liquid material into a reinforcing fiber base disposed in such a closed space.

  In the present invention, the term “reinforced fiber base material” refers to a reinforced fiber fabric, a knitted fabric, a braided fabric, a laminate of reinforced fiber fabrics such as papers made of reinforced fiber short fibers, or a reinforced fiber having a reinforced fiber as a triaxial woven fabric. An assembly with a certain thickness. In the reinforcing fiber substrate, there are gaps of the order of 50 μm between the reinforcing fiber fabrics, between the reinforcing fibers, and between these and the mold. The reinforcing fibers contained in the reinforcing fiber base are usually bundles of thousands to tens of thousands of single fibers, and the reinforcing fibers have a single fiber gap of the order of 5 μm between the single fibers.

  In addition, the shape of the reinforcement fiber base material which this invention makes object has a plate-shaped part. All of the reinforcing fiber bases may be plate-like, but the portion for impregnating the liquid and monitoring the impregnation state may be plate-like. It is supposed to be a laminate of reinforcing fiber materials or a single one, and mainly assumes that the bottom and surface averaged in a range larger than the size of the sound wave transmission / reception means face each other in parallel. As long as the propagation direction can be predicted, it may be a curved surface, a polygonal surface, or a surface with unevenness. In the present specification, the surface on the incident side of the sound wave is referred to as a first surface, and the surface opposite to the first surface is referred to as a second surface.

  The liquid material used in the present invention only needs to have fluidity as a whole, and is a thermoplastic resin, a simple liquid such as water, or a liquid containing a solid content (for example, a substance in which fine particles are dispersed). May be included. In the FRP molding, a thermosetting resin is mainly assumed, but not only a liquid at room temperature but also a material that flows at a molding temperature, such as a thermoplastic resin.

  The present inventors noticed that the prior art has determined that the impregnation is completed by filling the liquid material into the gap of the order of 50 μm in the reinforcing fiber substrate, and the liquid in the gap of the order of 50 μm is determined. When the body is filled, an unimpregnated portion of the liquid material remains between the single fibers, and the unimpregnated portion of the liquid material between the single fibers is gradually impregnated after the liquid material is filled into the gap of the order of 50 μm. It is clarified that the process proceeds, and it is possible to detect such a process by transmitting a sound wave and detecting the decrease in transmission intensity or reflection, and arrived at such a method. Usually, a mixture of a liquid and a solid such as a reinforcing fiber scatters sound waves due to non-uniform acoustic impedance, and its propagation is difficult, and the liquid propagates sound waves to the reinforcing fiber substrate being impregnated. No attempt was made to monitor the impregnation of the liquid material. In order to increase the propagation capability of sound waves, it is generally known that the center frequency of a sound wave sensor that transmits and receives sound waves is lowered and driven at a low frequency according to this. However, if the center frequency is lowered too much, the void detection performance will be reduced, and the pulse waveform inspection, which provides important information such as the thickness and flatness of the object to be measured, will also increase the pulse width, making it impossible to form the body of the pulse waveform. It becomes impossible to carry out.

  The inventors of the present invention have further studied earnestly about a sound wave sensor that can use a pulse waveform and can transmit a sound wave having a frequency capable of propagating through a thick reinforcing fiber base having a thickness of 50 ply or more, for example, 52 ply. A sound wave sensor with a center frequency of 400 to 600 kHz that can oscillate a pulse wave of 0.83 to 1.25 μs can be manufactured, and the sound wave can be propagated to a reinforced fiber base material impregnated with a liquid. As a result, it has been found that it is possible to provide a method capable of detecting the remaining of the unimpregnated portion with much higher accuracy. When the center frequency is lower than 400 kHz, the time width of the pulse wave may be longer, and when the center frequency is higher than 600 kHz, the propagation ability of the pulsed sound wave is insufficient and detection may be difficult. For the above reasons, the frequency is more preferably 450 to 550 kHz, and even more preferably 480 to 520 kHz.

  In the above description, the impregnation of the liquid material in the present invention is based on a process in which a fiber reinforced base material is disposed in the mold and the liquid material (liquid resin) is injected from the outside. When preparing a sheet-like reinforcing fiber substrate partially impregnated with a liquid resin in advance or a solid resin film at room temperature, such as partially impregnated prepreg or RFI, It also includes those that soften or melt and penetrate between the reinforcing fibers or between the reinforcing fiber layers.

  In the monitoring method of the first aspect of the present invention, a pulsed sound wave is transmitted from the first surface side of the reinforcing fiber base material, and the sound wave is propagated to the reinforcing fiber base material. The sound wave is received on the surface side of the liquid, and the impregnation state of the liquid material is monitored by the change of the received sound wave intensity. Before the liquid is impregnated, the gap between the reinforcing fibers is filled with gas or is in a vacuum state. Normally, sound waves cannot propagate through such a reinforcing fiber base material, but can propagate after impregnation of the liquid material, so that the state of impregnation of the liquid material can be measured. That is, by acquiring sound waves over time, the transition of the impregnation state of the liquid material into the reinforcing fiber base at that point can be detected from the change in the sound wave intensity received. The sound wave intensity propagating through the liquid material impregnated in the reinforcing fiber base may be smaller than the sound wave intensity when there is only the liquid material in the same propagation path. This is because the sound wave is scattered and attenuated. In such a case, even when sound waves are transmitted, they may propagate through the reinforcing fiber base impregnated with the liquid material and attenuate, and may not receive sufficient sound waves for observation. The center frequency of the sound wave sensor proposed in the present invention is preferable because it can increase the output of the sound wave to be transmitted and / or amplify and observe the received sound wave.

  Also, not only the state of impregnation of the liquid material into the reinforcing fiber substrate but also the sound wave propagation time that is the basis for determining the thickness can be measured with high accuracy, and the reinforcing fiber impregnated with the liquid material from the propagation time of the received sound wave The thickness of the substrate can be measured together.

  At this time, the peak value of the sound wave received by the sound wave sensor takes a minimum value when the liquid material is completely unimpregnated, and increases as the impregnation progresses. When the liquid is completely impregnated, the maximum value is reached and thereafter stabilized. The fact that the received sound wave intensity corresponds to the impregnation state can also be used.

  Further, the propagation time of the sound wave received by the sound wave sensor becomes longer as the thickness of the reinforcing fiber base becomes thicker and becomes shorter as the thickness becomes thinner. The thickness of the reinforcing fiber substrate can be obtained by multiplying the propagation time of the reinforcing fiber substrate by the propagation speed of the sound wave in the reinforcing fiber substrate. The propagation time of the reinforcing fiber base material can be obtained by subtracting the propagation time other than the reinforcing fiber base material from the entire propagation time.

  In addition, by arranging the sonic sensor along the impregnation direction of the liquid material, the highest value of the peak value of the sonic wave received by the sonic sensor at the position to be impregnated later (downstream), the sound wave at the position to be impregnated before (upstream) It is also possible to predict from the peak value taken by the sensor and determine the arrival at the final constant value at the downstream position.

In the monitoring method of the first reference aspect, a pulsed sound wave is transmitted from the first surface side of the reinforcing fiber substrate, the sound wave is propagated to the reinforcing fiber substrate, and the second surface of the reinforcing fiber substrate is used. Alternatively, the sound wave reflected on the second surface side is further propagated to the reinforcing fiber substrate, received on the first surface side, and the impregnation state of the liquid material is monitored by the change of the received sound wave intensity.

Similarly to the monitoring method of the first aspect described above, even if a sound wave is transmitted, a sufficiently strong sound wave is received unless the output of the transmitted sound wave is increased and / or the received sound wave is amplified. There are things that cannot be done. Usually, in the first reference form method, since the reflected sound wave further propagates through the reinforcing fiber base material impregnated with the liquid material once the sound wave has propagated, the intensity of the received sound wave is the same as that of the first embodiment. Smaller than described. Also in this case, if the center frequency of the sound wave to be used is in the above-described range, it is possible to increase the output of the sound wave to be transmitted and / or amplify the received sound wave and make the intensity sufficient for observation.

In this reference embodiment, with the above configuration, it receives on the side of the surface which has transmitted the wave of the reinforcing fiber substrate, transmitted and received by one wave sensor, after reducing the number of acoustic sensors, receives The impregnation state of the liquid material can be detected from the change in the sound wave intensity. By doing in this way, the man-hour concerning arrangement | positioning of a sound wave sensor and the cost of sensor itself can be reduced.

  At this time, the peak value of the sound wave received by the sound wave sensor takes a minimum value when the liquid material is completely unimpregnated, and increases as the impregnation progresses. When the liquid is completely impregnated, the maximum value is reached and thereafter stabilized. The fact that the received sound wave intensity corresponds to the impregnation state can also be used.

  In addition, by arranging the sonic sensor along the impregnation direction of the liquid material, the highest value of the peak value of the sonic wave received by the sonic sensor at the position to be impregnated later (downstream), the sound wave at the position to be impregnated before (upstream) It is also possible to predict from the peak value taken by the sensor and determine the arrival at the final constant value at the downstream position.

In the monitoring method of the second reference aspect of the present invention, a pulsed sound wave is transmitted from the first surface side of the reinforcing fiber substrate, propagated to the reinforcing fiber substrate, and reflected at the liquid impregnation interface. The reflected sound wave is received on the first surface side, and the impregnation state of the liquid material is monitored by the change of the received sound wave intensity.

Similar to the monitoring method of the first reference aspect described above, even when sound waves are transmitted, it may not be possible to receive sufficiently strong sound waves. In addition, if the impregnation interface is flat, reflection occurs due to the difference in acoustic impedance between the liquid impregnated part and the liquid non-impregnated part, but this interface is often not flat and receives sound waves of sufficient intensity. There are things that cannot be done. Usually, since the impregnation interface is disturbed by fluctuation of the impregnation speed of the liquid material due to the undulation of the reinforcing fiber base and no clear reflection occurs, the intensity of the sound wave to be received is the first aspect and the first reference. Smaller than that described in the embodiment. Also in this case, if the center frequency of the sound wave to be used is in the above-described range, it is possible to increase the output of the sound wave to be transmitted and / or to amplify the received sound wave and make the intensity sufficient for observation.

Also in this reference form, since it can receive by the side which transmitted the sound wave of the reinforced fiber base material by the said structure, transmission / reception can be performed with one sound wave sensor and the number of sound wave sensors can be reduced. By doing in this way, the man-hour concerning arrangement | positioning of a sound wave sensor and the cost of the sensor itself can also be reduced.

  At this time, the peak value of the sound wave received by the sound wave sensor takes a maximum value when the liquid material is completely unimpregnated, and decreases as the impregnation progresses. When the liquid is completely impregnated, the maximum value is reached and thereafter stabilized. It can also be used that the received sound wave intensity corresponds to the impregnation state.

  Furthermore, by observing the TOF (acoustic wave propagation time) from transmission to reception, it is also possible to specify where the liquid material impregnation interface is located.

The monitoring method of the present invention can be easily realized by using a monitoring device described below. In this monitoring apparatus, the sound wave transmitting means and the receiving means are essential. The center frequency of both the sound wave transmitting means and the sound wave receiving means is usually 400 kHz to 600 kHz. In the transmission method (first mode), the sound wave transmitting unit and the sound wave receiving unit paired with the sound wave transmitting unit are used. In the reflection method ( first and second reference modes), the sound wave transmitting unit and the sound wave receiving unit are used. Since the means can be performed by one sound wave sensor, a sound wave receiving means which is the same body as the sound wave transmitting means is used. The sound wave transmitting means and the sound wave receiving means preferably have the same center frequency and the same heat resistance, usable bandwidth, withstand voltage performance and the like. Furthermore, what has a center frequency of 450 to 550 kHz and can withstand an atmospheric temperature of 200 ° C. is suitable for the present invention. It has a means to acquire continuously the sound wave intensity of the sound wave obtained using the above-mentioned sound wave transmitting means and sound wave receiving means. As such acquisition means, a combination of an oscilloscope capable of simultaneously acquiring sound intensity of three or more channels and an amplifier used when the sound intensity is weak is desirable. Furthermore, what united these is suitable for this invention.

  Next, display means for displaying the temporal change (profile) of the sound wave intensity obtained as described above is prepared. As such display means, a general-purpose personal computer capable of analyzing the waveform sent from the acquisition means and displaying the result on a display with good visibility is desirable.

  By adopting the configuration as described above, it is possible to obtain an apparatus capable of obtaining a profile of sound wave intensity and detecting the impregnation state of the liquid material from a change in received sound wave intensity. If such an apparatus is used, the thickness of the reinforcing fiber base impregnated with the liquid material can also be measured from the propagation time of the received sound wave.

  Subsequently, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a side view schematically showing an embodiment of a method for monitoring the impregnation state of a liquid according to the present invention using a contact-type acoustic wave sensor. The hatched portion 11 represents a portion where the liquid impregnation is proceeding. The sonic sensor 2 is installed so as to sandwich the reinforcing fiber base 12 and the tool 13 in the vertical direction. A state in which a sound wave is transmitted from one of two sound wave sensors facing in the vertical direction and received by the other is shown.

  In the present invention, by measuring the sound wave in this way, the portion that is not impregnated with the liquid material contains a large amount of air or vacuum in the gap between the reinforcing fibers, so that the sound wave is not transmitted, and the liquid material is completely in the vertical direction. It is possible to detect the state of impregnation of the liquid material by reading that the sound wave is transmitted through the part that has been completely impregnated from the change of the sound wave intensity.

  Although three pairs of sonic sensors are shown in FIG. 1, this number may be four pairs or more or two pairs or less as required.

  Furthermore, in FIG. 1, the sonic sensor 2 is installed up and down, but the sonic wave is refracted inside or on the surface of the reinforcing fiber base 12 or the tool 13, and the sonic wave transmitted from one side cannot be measured with sufficient intensity. May be installed at a position where sufficient strength can be secured by shifting the position of the other acoustic wave sensor by calculation and / or trial and error.

  Furthermore, when the sound wave transmitted from one of the sound wave sensors propagates through a part of the liquid-impregnated portion 11 and is reflected somewhere, the other sound wave sensor is installed at the reflection destination and received. Alternatively, the reflected sound wave may return to the original position and be received by the transmitted sound wave sensor itself.

  FIG. 2 is a plan view of FIG. In FIG. 2, the plurality of sound wave sensors 2 are installed in a straight line position. However, the sound wave may be transmitted to or received from the sound wave sensor that is opposed to the reinforcing fiber base material with the tool interposed therebetween. If possible, an arbitrary number may be installed in an arbitrary place as necessary. The hatched portion 11 represents a portion where the liquid impregnation is proceeding.

  3 and 4 show a procedure for installing the acoustic wave sensor 2.

  First, as shown in FIG. 3, the adhesive 31 is applied to the surface where the sonic sensor fixing means 22 is brought into contact with the monitoring object 3, and then adhered to the monitoring object 3. Next, as shown in FIG. 4, the contact medium 32 (hatched portion) is applied to the surface of the ultrasonic sensor main body 21 that comes into contact with the monitoring target 3 into the hole that penetrates the bonded and fixed ultrasonic sensor fixing means 22. This shows a situation where the monitoring object 3 is closely attached.

  In the present invention, by installing the sound wave sensor 2 in such a procedure, the measurement can be repeated any number of times without destroying the sound wave sensor 2, and the sound wave sensor can be prevented from moving and shifting during the measurement. Thus, it is possible to detect the state of impregnation of the liquid material. This is particularly effective in the FRP resin impregnation process in which the thickness of the monitoring target varies. As an example of the resin impregnation step of FRP whose thickness changes, a resin impregnation step of vacuum RTM molding can be mentioned. In vacuum RTM molding, a reinforcing fiber base material is disposed on a lower mold, a closed space (molding cavity) is formed by a sealing material and a film material, and the molding cavity is evacuated to impregnate the reinforcing fiber base material with a liquid. The liquid material is at atmospheric pressure, and when the reinforcing fiber base material is impregnated, the film material attached to the reinforcing fiber base material is pushed up by a vacuum, and the reinforcing fiber base material impregnated with the liquid material is the object of monitoring. The thickness of becomes thicker. In addition, after the liquid material is completely impregnated into the reinforcing fiber base material, an operation called bleed is performed in which the injection of the liquid material is stopped and vacuuming is continued. At the time of bleed, the surplus liquid material is discharged from the reinforcing fiber base, and the thickness is reduced.

  Note that the sonic sensor fixing means is bonded to the monitoring target. For example, when the monitoring target itself has magnetism, the sonic sensor fixing means may be made of a magnetic material and bonded by magnetic force, and is limited to bonding with an adhesive. Is not to be done.

  5 and 6 show a procedure for installing the acoustic wave sensor 2 from the vertically downward direction.

  First, as shown in FIG. 5, after installing the sound wave sensor main body 21 in the same manner as in FIGS. 3 and 4, the fixing means 33 is inserted into the hole penetrating from the side surface portion of the sound wave sensor fixing means 22 to the center. Yes. Next, as shown in FIG. 6, the sound wave sensor main body 21 is fastened by the fixing means 33. Here, a bolt or a screw can be used as the fixing means 33.

  In the present invention, by fastening the sonic sensor main body 21 in such a procedure, the sonic sensor is prevented from falling vertically downward, stably detecting the impregnation state of the liquid material, and as necessary. Thickness can be measured.

  FIG. 7 is a side view schematically showing an embodiment of a monitoring method of the liquid material impregnation state using the air propagation type acoustic wave sensor according to the present invention. The hatched portion 11 represents a portion where the liquid impregnation is proceeding. An airborne acoustic sensor 4 is installed so as to sandwich the reinforcing fiber base 12 and the tool 13 in the vertical direction. A state in which a sound wave is transmitted from one of two sound wave sensors facing in the vertical direction and received by the other is shown.

  In the present invention, by measuring the sound wave in this way, as in the situation of FIG. 1, the sound wave does not pass through the portion where the liquid material is not impregnated because the gap between the reinforcing fibers contains a lot of air or vacuum. It is possible to detect the state of impregnation of the liquid material by reading that the sound wave is transmitted through the part where the liquid material is completely impregnated in the vertical direction from the change in the sound wave intensity.

  Moreover, in FIG. 7, since the sound wave sensor 4 is arranged at a distance from the reinforcing fiber base 12 and the tool 13, the sound wave sensor 4 is moved during monitoring as long as the sound wave sensor 4 is synchronized with the opposing sound wave sensor. be able to.

  Further, in FIG. 7, the sonic sensor 4 is installed at the top and bottom, but the sonic wave is refracted inside or on the surface of the reinforcing fiber base 12 or the tool 13, and the sonic wave transmitted from one side cannot be measured with sufficient intensity. As in the situation of FIG. 1, the other long sound sensor may be installed at a position where sufficient strength can be secured by shifting the position by calculation and / or trial and error.

  Further, when the sound wave transmitted from one of the sound wave sensors propagates through a part of the liquid-impregnated portion 11 and is reflected somewhere, as in the situation of FIG. Even if a sound wave sensor is installed and received, it may return to the original position as a result of reflection, and may be received by the transmitted sound wave sensor itself.

  FIG. 8 is a plan view of FIG. FIG. 8 shows a situation in which the sound wave sensor 4 can move horizontally in any direction. As long as the sound wave can be transmitted to the sound wave sensor opposed to the reinforcing fiber substrate and the tool or the sound wave from the sound wave sensor can be received, any number of the sound wave sensors may be installed at any place as necessary.

  In the present invention, by measuring the sound wave in the air propagation method in this way, even when monitoring the impregnation state of the liquid material into the reinforcing fiber base material having a large size, a small number of sound wave sensors can be used for a wide range of liquid state. The body impregnation status can be detected, and the thickness can be measured as necessary.

[Reference Example] Preparation of resin composition “Araldite” (registered trademark) MY-721 (N, N, N ′, N′-tetraglycidyl-4,4′-diaminodiphenylmethane, manufactured by Huntsman Advanced Materials) 40 parts by weight, “JER” (registered trademark) 630 (N, N, O-triglycidyl-p-aminophenol, manufactured by Japan Epoxy Resin Co., Ltd.), 25 parts by weight, “Epon” (registered trademark) 825 (bisphenol A) 35 parts by weight of diglycidyl ether (manufactured by Japan Epoxy Resin Co., Ltd.) was added, and the mixture was stirred at 70 ° C. for 1 hour to obtain an epoxy main agent. Further, "JER Cure" (registered trademark) W (diethyltoluenediamine, manufactured by Japan Epoxy Resin Co., Ltd.) 26.6 parts by weight, 3,3'-DAS (3,3'-diaminodiphenylsulfone, manufactured by Mitsui Chemicals Fine Co., Ltd.) After adding 11.4 parts by weight, the mixture was stirred at 100 ° C. for 1 hour, and then cooled to 70 ° C. Subsequently, 1 part by weight of TBC (t-butylcatechol, manufactured by Ube Industries) was added as a curing accelerator, and the mixture was further stirred at 70 ° C. for 30 minutes to uniformly dissolve TBC as a curing agent.

That is, an epoxy resin composition was prepared by mixing 39 parts by weight of a curing agent with 100 parts by weight of the epoxy main agent.
[Example 1]
As shown in FIG. 1, in a resin impregnation process at the time of manufacturing an FRP structure, a stainless steel tool 13 having a size of 300 mm × 600 mm and a thickness of 10 mm is installed while supporting about 100 mm on both left and right sides in the direction in FIG. . A mold release treatment was performed thereon, and a reinforcing fiber base 12 using carbon fibers as reinforcing fibers of 100 mm × 400 mm was disposed. This reinforcing fiber base 12 has a pseudo-isotropic laminated structure and is a laminate of 52 carbon fiber fabrics (CZ8431DP, T800 unidirectional fabric manufactured by Toray Industries, Inc.). From above, a bagging film was covered so as to be sealed. Although omitted in the drawings, the release cloth and the resin diffusion medium were sandwiched between the reinforcing fiber base and a tool or bagging film, and the bagged reinforcing fiber base was decompressed and heated to 70 degrees. By arranging in this way, the resin (liquid material) that has flowed in from the upper left of the reinforcing fiber base in FIG. 1 flows into the uppermost layer first to form a resin reservoir, so as to impregnate from the upper side to the lower side, Then, it was made to flow from the left side to the right side, and as a result, it was adjusted so that the resin could be impregnated from the upper left side to the lower right side. As the resin, the epoxy resin composition of the above reference example was used.

  Next, as shown in FIGS. 1 and 2, six acoustic wave sensors 2 (manufactured by Japan Probe Co., Ltd., B0.5C20N) were installed from above the bagging film and under the tool 13. Each sonic sensor has a 100 mm × 400 mm region from above the reinforcing fiber substrate covered with the bagging film and from the bottom of the tool, on the upper and lower central axes in the direction in FIG. As shown, the sound wave sensors at the center were arranged in the longitudinal direction so as to come to the center of a region of 100 mm × 400 mm.

  Thereafter, a function generator (manufactured by Hewlett-Packard Co., Ltd., 8116A) is connected to the three acoustic wave sensors 2 installed on the reinforcing fiber base 12 side via a high frequency power source (manufactured by NF Circuit Block Co., Ltd., HSA 4101). A pulse voltage having a wave height of 130 V was input. Next, an oscilloscope (manufactured by Tektronix Co., Ltd., TDS744A) is connected to the three sound wave sensors 2 installed on the tool 13 side, and the three sound wave sensors installed on the tool 13 side that detect the sound wave propagated through the resin-impregnated portion. The voltage waveform obtained from 2 was monitored. The results are shown in FIG. 9 with the resin injection start time being 0 seconds.

  In the configuration of FIGS. 1 and 2, the state of impregnation of the liquid material at three positions can be monitored, and the channels are set to 1 to 3 from the left. As shown in FIG. 9, the resin flows from the left to the right, and the sound wave intensity gradually increases according to the resin impregnation state at each measurement point as time elapses. The increase in strength stops. The sound wave intensity here means 1.0 (complete resin impregnation) when the maximum voltage peak value is observed by the reception-side acoustic wave sensor, and 0.0 (resin unimpregnated) when the minimum peak value is observed. ).

  Here, since it is read that the resin is completely impregnated into the reinforcing fiber base up to the measurement point of 3ch at the point of 1160 seconds, the resin injection is stopped, the temperature is raised to 130 ° C., the resin is cured, and then cut. When the cross section of the CFRP was inspected, it was confirmed that the resin was completely impregnated up to 3ch. Thus, the liquid impregnation situation could be monitored.

FIG. 11 shows the propagation time of the sound waves of the two channels. As shown in FIG. 11, the elapsed time from the start of resin injection increases in 800 to 1300 seconds and decreases after 1300 seconds. Specifically, the initial value is 9.76 μsec, the longest value is 10.01 μsec, the shortest value is 9.20 μsec, and the sound wave propagation time of the tool 10 mm is known to be 2.00 μsec, and the tool is excluded. The propagation times are 7.76 μsec, 8.01 μsec, and 7.20 μsec, respectively. Except for the tool, the sound wave propagates in the reinforced fiber base material, film, and auxiliary materials, and the film and auxiliary materials are usually thin, so the propagation time excluding the tool approximates the propagation time in the reinforced fiber base material. be able to. It is known that sound waves propagate at a speed of 1300 m / sec in the reinforcing fiber base, and by multiplying this speed by the propagation time, the initial thickness of the reinforcing fiber base is increased from 10.09 mm to 10.41 mm. It turns out that it became thin finally to 9.36 mm. In this way, the thickness of the reinforcing fiber substrate could be monitored.
[Example 2]
As shown in FIG. 7, in the resin impregnation process at the time of manufacturing the FRP structure, a stainless steel tool 13 having a size of 400 mm × 400 mm and a thickness of 20 mm was installed with supporting both left and right ends of about 100 mm in the direction in FIG. . A mold release treatment was performed thereon, and a reinforcing fiber base 12 using carbon fibers as reinforcing fibers of 200 mm × 200 mm was disposed. The laminated configuration of the reinforcing fiber base 12, the matters omitted in the drawing, and the flow direction of the resin were the same as in Example 1.

  Next, as shown in FIGS. 7 and 8, two aerial propagation type acoustic wave sensors 4 (manufactured by The Ultra Group, NCG500-D19-P50) were disposed on the bagging film and below the tool 13. Each acoustic wave sensor was placed at the center in the horizontal direction in FIG. 8 in an area of 200 m × 200 mm, 40 mm away from the top of the reinforcing fiber substrate covered with the bagging film and 20 mm away from the bottom of the tool.

  Thereafter, a pulsar receiver (manufactured by The Ultra Group, NCA1000) was connected to the acoustic wave sensor 4 disposed on the reinforcing fiber base 12 side, and a chirped wave voltage with a center frequency of 500 kHz was input. Next, the sound wave sensor 4 disposed on the tool 13 side was also connected to the pulsar receiver, and the voltage waveform obtained from the sound wave sensor 4 disposed on the tool 13 side that detected the sound wave propagated through the resin-impregnated portion was monitored. This result is shown in FIG. 10 with the resin injection start time as 0 second.

  7 and 8, it is possible to monitor the impregnation state of the liquid material at one point. Further, the air propagation type acoustic wave sensor 4 may be moved to any position as long as it is synchronized with the opposing acoustic wave sensor. However, if there is a suddenly different temperature distribution in the space between the measurement target and the probe, the air density and sound velocity change due to the distribution, and reflection or refraction occurs due to the difference in acoustic impedance, so that the sound wave reaches the opposing sound wave sensor 4. It was necessary to keep the ambient temperature around the monitoring system constant with attention to this point.

As shown in FIG. 10, the resin flows from the left to the right, and the sound wave intensity increases according to the resin impregnation state at the measurement point with the passage of time. When the impregnation is completed at each measurement point, the sound wave intensity is increased. The rise stops. As the resin, the epoxy resin composition of the reference example was used. The sound wave intensity referred to here is 1.0 (resin complete impregnation) when the maximum voltage peak value is observed by the reception-side acoustic wave sensor, and 0.0 (resin when the minimum voltage peak value is observed. Unimpregnated). It is read that the resin is completely impregnated into the reinforcing fiber base at 1000 seconds. Thus, the liquid impregnation situation could be monitored.
[Example 3]
As shown in FIG. 1, the voltage waveforms obtained from the three sound wave sensors 2 installed on the side of the tool 13 that detects the sound wave propagated through the resin impregnated portion 11 can be monitored with the same configuration as in the first embodiment. The resin and the flow direction of the resin were also the same as in Example 1.

  Immediately after the transmittance measured by the sonic sensor 2 located on the leftmost side in FIG. 1 was stabilized at the maximum value, the resin injection was stopped, and the temperature was raised to 130 ° C. and cured. At this time, the transmittance of the sound wave sensor 2 located in the center was 0.8, and the transmittance measured by the sound wave sensor 2 located on the rightmost side was 0.1. When the cross section of the CFRP is cut and inspected, the resin is completely impregnated in the thickness direction at the position of the leftmost acoustic sensor, and at the position of the central acoustic sensor, the short fiber gap or reinforcing fiber base in the reinforcing fiber bundle is Unimpregnated parts are interspersed in gaps between materials, etc. First, the unimpregnated part of gaps between reinforcing fiber bases decreases as the position of the leftmost acoustic sensor moves from the central acoustic sensor position. After that, it was observed that the unimpregnated portion of the short fiber gap in the reinforcing fiber bundle disappeared. In addition, although the resin reached | attained at the position of the rightmost sound wave sensor, the substantially unimpregnated part was spreading. Thus, the impregnation state of the liquid material can be monitored, and the resin is completely impregnated in the thickness direction at the position where the transmittance is 1.0, and the position is surely reached. An FRP structure impregnated with resin could also be produced.

  The method for monitoring the state of impregnation of the liquid material of the present invention described above is preferably applied to a method for manufacturing an FRP structure in which a reinforcing resin is impregnated with a liquid resin, but the application target is not limited thereto, for example, It can also be suitably used for confirming the impregnation status when the fiber assembly is impregnated with a treatment solution and subjected to some physical or chemical treatment.

It is a side view which represents typically one Embodiment of the molding condition monitoring method of the fiber reinforced plastic using the contact-type sound wave sensor concerning this invention. It is a top view of FIG. It is a figure showing the method of installing a sound wave sensor fixing means. It is a figure showing the method of installing a sound wave sensor main body in a sound wave sensor fixing means. It is a figure showing the condition which is going to install the sound wave sensor main body upward by a fixing means. It is a figure showing the condition which installed the sound wave sensor main body upward by the fixing means. It is a side view which represents typically one Embodiment of the molding condition monitoring method of the fiber reinforced plastic using the sound wave sensor of the air propagation system concerning this invention. It is a schematic diagram of FIG. It is a graph which shows the transition of the sound intensity of the sound wave in the structure of FIG. It is a graph which shows the transition of the sound wave intensity of the sound wave in the structure of FIG. It is a graph which shows the transition of the propagation time of the sound wave in the structure of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid impregnation direction 11 Liquid impregnation part 12 Reinforcement fiber base material 13 Tool 2 Sound wave sensor 21 Contact type sound wave sensor main body 22 Sound wave sensor fixing means 3 Monitoring object 31 Adhesive 32 Contact medium 33 Fixing means 4 Air propagation method Sonic sensor

Claims (5)

In the impregnation process of the liquid material into the reinforcing fiber base having a plate-like portion arranged in the mold, a pulsed sound wave is transmitted from the first surface side of the reinforcing fiber base, The sound wave is received on the side of the surface 2, and the impregnation state of the liquid material is detected by the change of the received sound wave intensity, and the thickness of the reinforcing fiber base impregnated with the liquid material is determined from the propagation time of the received sound wave. A method for monitoring the molding status of fiber reinforced plastics, characterized by Using the fact that the sound wave intensity increases from the value obtained when the liquid material is not impregnated as the impregnation of the liquid material proceeds and finally becomes a constant value, the state of impregnation of the liquid material is determined. The method for monitoring the molding status of the fiber-reinforced plastic according to claim 1, wherein the method is detected. The sound wave intensity is measured at a plurality of positions in the impregnation direction of the liquid material, and the maximum value of the sound wave intensity is obtained from the change of the sound wave intensity at the upstream position, thereby obtaining a final constant value at the downstream position. The method for monitoring the molding status of the fiber-reinforced plastic according to claim 2 , wherein arrival is determined. The method for monitoring a molding state of a fiber reinforced plastic according to any one of claims 1 to 3 , wherein the pulsed sound wave has a time width of 0.83 to 1.25 µsec. A method for producing a fiber reinforced plastic in which a reinforced fiber base material is impregnated with a liquid resin, wherein the impregnation step is controlled by detecting the resin impregnation state by the molding state monitoring method according to any one of claims 1 to 4. A method for producing a fiber-reinforced plastic, comprising:

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