CN116968412A - Composite material intelligent repair structure and preparation and health self-detection method thereof - Google Patents
Composite material intelligent repair structure and preparation and health self-detection method thereof Download PDFInfo
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- CN116968412A CN116968412A CN202310832376.8A CN202310832376A CN116968412A CN 116968412 A CN116968412 A CN 116968412A CN 202310832376 A CN202310832376 A CN 202310832376A CN 116968412 A CN116968412 A CN 116968412A
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- 239000002131 composite material Substances 0.000 title claims abstract description 155
- 230000008439 repair process Effects 0.000 title claims abstract description 68
- 238000001514 detection method Methods 0.000 title claims abstract description 37
- 230000036541 health Effects 0.000 title claims abstract description 24
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 239000003822 epoxy resin Substances 0.000 claims abstract description 180
- 229920000647 polyepoxide Polymers 0.000 claims abstract description 180
- 239000006229 carbon black Substances 0.000 claims abstract description 89
- 239000011159 matrix material Substances 0.000 claims abstract description 13
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 43
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 34
- JDVIRCVIXCMTPU-UHFFFAOYSA-N ethanamine;trifluoroborane Chemical compound CCN.FB(F)F JDVIRCVIXCMTPU-UHFFFAOYSA-N 0.000 claims description 31
- 238000001723 curing Methods 0.000 claims description 27
- 229920000049 Carbon (fiber) Polymers 0.000 claims description 26
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- 239000004744 fabric Substances 0.000 claims description 22
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C73/00—Repairing of articles made from plastics or substances in a plastic state, e.g. of articles shaped or produced by using techniques covered by this subclass or subclass B29D
- B29C73/04—Repairing of articles made from plastics or substances in a plastic state, e.g. of articles shaped or produced by using techniques covered by this subclass or subclass B29D using preformed elements
- B29C73/10—Repairing of articles made from plastics or substances in a plastic state, e.g. of articles shaped or produced by using techniques covered by this subclass or subclass B29D using preformed elements using patches sealing on the surface of the article
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C73/00—Repairing of articles made from plastics or substances in a plastic state, e.g. of articles shaped or produced by using techniques covered by this subclass or subclass B29D
- B29C73/24—Apparatus or accessories not otherwise provided for
- B29C73/26—Apparatus or accessories not otherwise provided for for mechanical pretreatment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/12—Layered products comprising a layer of synthetic resin next to a fibrous or filamentary layer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
- B32B27/26—Layered products comprising a layer of synthetic resin characterised by the use of special additives using curing agents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/38—Layered products comprising a layer of synthetic resin comprising epoxy resins
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64F—GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
- B64F5/00—Designing, manufacturing, assembling, cleaning, maintaining or repairing aircraft, not otherwise provided for; Handling, transporting, testing or inspecting aircraft components, not otherwise provided for
- B64F5/40—Maintaining or repairing aircraft
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
- G01B7/18—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/20—Investigating the presence of flaws
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C73/00—Repairing of articles made from plastics or substances in a plastic state, e.g. of articles shaped or produced by using techniques covered by this subclass or subclass B29D
- B29C73/24—Apparatus or accessories not otherwise provided for
- B29C73/26—Apparatus or accessories not otherwise provided for for mechanical pretreatment
- B29C2073/262—Apparatus or accessories not otherwise provided for for mechanical pretreatment for polishing, roughening, buffing or sanding the area to be repaired
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
- B32B2262/10—Inorganic fibres
- B32B2262/106—Carbon fibres, e.g. graphite fibres
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2605/00—Vehicles
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- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
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- Health & Medical Sciences (AREA)
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- General Health & Medical Sciences (AREA)
- Electrochemistry (AREA)
- Immunology (AREA)
- Life Sciences & Earth Sciences (AREA)
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Abstract
The invention relates to the technical field of composite material intelligent repair structures, in particular to a composite material intelligent repair structure and a preparation and health self-detection method thereof. The epoxy resin and carbon black composite film comprises an insulating matrix and an epoxy resin and carbon black composite film sensing element, and the epoxy resin and carbon black composite film sensing element is distributed along three different directions at each measuring point and has a strain resistance effect. Due to the strain resistance effect, when the composite material repair structure is deformed under external load or the structure is damaged such as layering, debonding and the like, the resistance of the health detection element is changed, and the strain data of the health detection point can be obtained by utilizing the Wheatstone bridge and calibration experimental data and outputting voltage through the bridge. The main strain of each measuring point can be obtained by utilizing the line strain of each measuring point along three directions.
Description
Technical Field
The invention relates to the technical field of composite material intelligent repair structures, in particular to a composite material intelligent repair structure and a preparation and health self-detection method thereof.
Background
The proportion of the composite material of the whole machine of the current foreign latest generation aircraft such as the air passenger A350 and the Boeing B787 aircraft exceeds 50 percent. With the action of service time, external load, accidental events and environment, damage and degradation of the aircraft composite material are accumulated continuously, and damage such as layering, degumming, surface scratch, hole edge damage, impact damage, war injury, cracks and the like can occur.
Because the composite material structure used by the aircraft is mostly prepared by an integral hot press molding process, local repair of the damaged part of the composite material structure on the premise of ensuring the safety of the aircraft is the most economical and effective way for maintaining the original navigability of the aircraft and reducing the maintenance manpower and cost. The existing repair technology and repair method of the composite material mainly comprise rapid repair technologies such as filling and pouring repair, mechanical connection repair, cementing repair, resin injection repair, microwave repair, electron beam curing repair, photo curing repair and the like. In addition, as the length of service increases, the interior of the aircraft composite structure may experience degradation in mechanical properties due to the accumulation of damage and degradation. The structural properties of the repaired composite material are different from the mechanical properties and the properties of the aircraft composite material structural body in a damaged state. Because of the mismatch of the strength and the rigidity of the aircraft composite material, the aircraft composite material repair structure and the aircraft composite material body structure are extremely easy to damage and destroy. Therefore, the reliable mechanical property of the aircraft composite material repair structure in the service process is ensured to be very critical to the flight safety and environmental adaptability of the aircraft composite material repair structure and even the whole aircraft, and the method has important significance for carrying out self-detection on the health state of the composite material repair structure, accurately and timely discovering the damage inside the repair structure and ensuring the flight safety of the aircraft.
At present, structural health detection is mainly realized by embedding sensors such as strain, piezoelectricity or optical fibers and the like into a composite material. By analyzing the data of the embedded sensor, the structural health problems of composite material degumming, layering, matrix structure crack growth and the like are obtained. Although the method can realize the detection of the health state of the structure, the rigidity and the strength of the sensor and the composite material structure are obviously mismatched due to different materials of the sensor and the composite material structure, and the stress in the composite material structure is uneven due to the influence of the interface effect of the composite material and the embedded sensor, so that the phenomenon of degumming and layering at the position of the sensor is extremely easy to occur, and the service life of the aircraft repair structure is influenced. Other structural health detection methods, such as ultrasound, are also applied to detection of defects inside structures, but ultrasound signals are not sufficiently sensitive to air holes, inclusions and are less intuitive to detect and prone to missed detection.
Disclosure of Invention
In order to solve the technical problems, the invention provides an intelligent repair structure of a composite material and a preparation and health self-detection method thereof. The high-precision health self-detection aircraft repair structure based on stress test evaluation is prepared, and a corresponding detection method is designed, so that the purpose of health detection of the aircraft repair structure is achieved.
The technical problems to be solved by the invention are realized by adopting the following technical scheme:
the intelligent repair structure of the composite material comprises an epoxy resin film, a composite film of epoxy resin and carbon black and carbon fiber cloth, wherein the epoxy resin film, the composite film of epoxy resin and carbon black and the carbon fiber cloth are paved according to a certain layering mode and are cured by a resin film melting and dipping process, and the epoxy resin film is paved between the composite film of epoxy resin and carbon black and the carbon fiber cloth.
Preferably, the certain layering mode is that the first layer is an epoxy resin film, the second layer is carbon fiber cloth, the third layer is an epoxy resin film, the fourth layer is an epoxy resin and carbon black composite film, the fifth layer is an epoxy resin film, the sixth layer is carbon fiber cloth and the seventh layer is an epoxy resin film.
Preferably, the epoxy resin and carbon black composite film is formed by compounding an insulating matrix and an epoxy resin and carbon black composite film sensing element, wherein the insulating matrix is prepared by mixing epoxy resin and a high-temperature curing agent, and the carbon black composite film sensing element is prepared by mixing epoxy resin, a high-temperature curing agent and carbon black.
Preferably, monitoring points are arranged on the carbon black composite film sensing element and correspondingly distributed along the directions of 0 degree, 90 degrees and 135 degrees.
A preparation method of an intelligent repair structure of a composite material is used for preparing the intelligent repair structure of the composite material, and comprises the following steps:
polishing the repair area of the aircraft composite material belt according to the data of the damage size and the damage depth of the surface of the aircraft composite material structure to form a groove to-be-repaired area;
cutting the flaky carbon fiber cloth, the epoxy resin film and the epoxy resin and carbon black composite film according to the size of the area to be repaired of the groove;
step three, determining the number of layers and the layer direction of the carbon fiber sheet according to the depth of the to-be-repaired area of the groove, and performing layer according to a certain layer mode;
and (IV) after the layering is completed, coating the layering by using a hot-pressing vacuum bag, vacuumizing by using a vacuum pump, discharging air, heating by using a resin film infiltration process to melt and impregnate the epoxy resin film and the epoxy resin and carbon black composite film, and curing and forming the intelligent repair structure of the composite material after a certain time.
Preferably, the epoxy resin film is prepared as follows:
weighing a proper amount of epoxy resin in a beaker, adding glycol according to a certain mass ratio, and fully stirring, diluting and dissolving;
weighing a proper amount of boron trifluoride monoethylamine in a beaker according to the required mass fraction, and adding ethylene glycol according to a certain mass proportion to fully stir, dilute and dissolve;
step (C), mixing the dissolved boron trifluoride monoethylamine solution with epoxy resin solution, and then carrying out ultrasonic oscillation for 30min in a room temperature environment to fully mix a boron trifluoride monoethylamine curing agent with epoxy resin;
step (D), placing the mixed epoxy resin and boron trifluoride monoethylamine solution in a vacuum oven at 100-140 ℃ for 2h for prepolymerization;
and (E) taking out the epoxy resin after the pre-polymerization treatment in a vacuum oven, and scraping out the epoxy resin film with a certain thickness by using a special cutter.
Preferably, the preparation process of the epoxy resin and carbon black composite film is as follows:
weighing a proper amount of epoxy resin in a beaker, adding glycol according to a certain mass ratio, and fully stirring, diluting and dissolving;
weighing a proper amount of boron trifluoride monoethylamine in a beaker according to the required mass fraction, and adding ethylene glycol according to a certain mass proportion to fully stir, dilute and dissolve;
step (c), weighing a proper amount of conductive carbon black powder in a beaker according to the required mass fraction, adding ethylene glycol according to a certain proportion, and oscillating for 30min by using ultrasound to fully dissolve;
step (d), mixing the conductive carbon black solution and the epoxy resin solution, and then carrying out ultrasonic vibration for 1-2h in a room temperature environment;
pouring the dissolved boron trifluoride monoethylamine solution into a mixed solution of epoxy resin and carbon black, and then carrying out ultrasonic oscillation for 30min in a room temperature environment to fully mix a boron trifluoride monoethylamine curing agent, the epoxy resin and the carbon black;
pouring the mixed solution of the epoxy resin, the boron trifluoride monoethylamine and the carbon black into a corresponding cavity of a special mold, pouring the mixed solution of the epoxy resin and the boron trifluoride monoethylamine into other cavities, and placing the cavities in a vacuum oven at 100-140 ℃ for prepolymerization for 30min;
taking out the die from the vacuum oven, rapidly drawing out the baffle plates between the chambers, and then putting the die back into the vacuum oven again to continue prepolymerization for 1.5h at 100-140 ℃;
and (h) taking out the epoxy resin and carbon black compound which are subjected to the pre-polymerization treatment in a vacuum oven, and scraping out the epoxy resin and carbon black compound film with a certain thickness by using a special cutter.
A health self-detection method for a composite material intelligent repair structure is used for detecting the composite material intelligent repair structure and comprises the following steps:
step (S1), respectively connecting wires corresponding to the epoxy resin in the epoxy resin and carbon black composite film and the carbon black composite film sensing element into a Wheatstone bridge according to a 1/4 bridge connection mode;
step (S2), according to the relation between the calibrated sensing element and the relative variable quantity of the resistor, obtaining the line strain values of all monitoring points along different directions by reading the variable value of the output voltage of the Wheatstone bridge circuit;
and step (S3) utilizing the detection of the line strain values of the monitoring points in different directions to obtain the maximum main strain direction and the maximum main strain size of the monitoring points, analyzing the positions of the layers of the composite material repairing structure, which are easy to cause defects and damages, and realizing the self-detection of the structural health.
Preferably, the strain value of the repair structure deformation is obtained in step (S2) from the wheatstone bridge output voltage:
wherein E is the power supply voltage of a Wheatstone bridge; k is the sensitivity coefficient of the sensing element, and is obtained through a calibration experiment; epsilon is a line strain value of the monitoring point along the axis direction of the sensing element; u (U) out And outputs a voltage for the bridge.
Preferably, in the step (S3), the maximum main strain direction and the maximum main strain size of the monitoring points can be obtained by detecting the line strain values of the monitoring points in different directions:
the point along a certain direction line strain and the point each strain satisfy the following conditions:
ε＝ε x cos 2 θ+γ xy sinθcosθ+ε y sin 2 θ
testing the linear strain of a point along three different directions (0 DEG, 90 DEG and 135 DEG), and obtaining the strain value corresponding to the detection point:
the main strain size and direction corresponding to the detection point satisfy:
the main strain magnitude and direction and strain values along 0 °,90 ° and 135 ° by testing out a point satisfy:
the beneficial effects of the invention are as follows:
(1) The invention solves the problems of rigidity mismatch and the like caused by different materials of the traditional embedded sensor, and avoids the change of the internal stress of the composite material structure caused by the embedding of the sensor;
(2) The invention can realize the self-detection of the health state of the composite material repairing structure;
(3) The invention can realize the detection of the deformation of the same layer at different points and the deformation states of different layers of the composite material repairing structure, and can determine the magnitude and the direction of the deformation main strain
(4) The invention can determine the position and the layer number of the damage of the composite material structure and provide a solution for the internal damage test of the composite material structure
(5) The invention can be used for detecting the real-time deformation and stress state of the composite material repair structure in the service state.
Drawings
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
FIG. 1 is a schematic diagram of a composite intelligent repair structure layering structure;
FIG. 2 is a schematic diagram of a mold structure for preparing a composite film of epoxy resin and carbon black;
FIG. 3 is a schematic diagram of a composite film of epoxy resin and carbon black;
FIG. 4 is a test circuit diagram of a composite intelligent repair structure;
FIG. 5 is a schematic diagram of an intelligent repair structure for a composite material.
In the figure: 1. an epoxy resin film; 2. an epoxy resin and carbon black composite film; 3. a carbon fiber cloth; 4. an epoxy resin and carbon black composite membrane cavity; 5. an epoxy cavity; 6. a chamber dividing baffle; 7. an insulating base; 8. an epoxy resin and carbon black composite film sensing element; 9. a composite patch; 10. and (5) repairing the structural matrix of the composite material.
Detailed Description
In order that the manner in which the invention is attained, as well as the features and advantages thereof, will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings.
As shown in fig. 1, the intelligent repair structure of the composite material comprises an epoxy resin film 1, a composite film 2 of epoxy resin and carbon black and carbon fiber cloth 3, wherein the composite film 2 of epoxy resin and carbon black and the carbon fiber cloth 3 are paved according to a certain layering mode and are solidified by a resin film melting and dipping process. The specific layering mode is that the first layer is an epoxy resin film 1, the second layer is a carbon fiber cloth 3, the third layer is an epoxy resin film 1, the fourth layer is an epoxy resin and carbon black composite film 2, the fifth layer is an epoxy resin film 1, the sixth layer is a carbon fiber cloth 3, and the seventh layer is an epoxy resin film 1.
The epoxy resin film 1 is paved between the epoxy resin and carbon black composite film 2 and the carbon fiber cloth 3. And the carbon fiber cloth 3 is prevented from being in direct contact with the epoxy resin and carbon black composite film 2, so that the strain resistance effect of the epoxy resin and carbon black composite film 2 is prevented from being influenced.
The epoxy resin and carbon black composite film 2 can be a film-shaped structural material prepared by blending epoxy resin and carbon black, can be prepared by blending epoxy resin and graphene, and can be prepared by mixing epoxy resin and nanoparticle silver powder. I.e., a material that can form a component having a strain resistance effect after the epoxy resin and any other material have been subjected to a blending process, and that does not adversely affect the subsequent curing of the epoxy resin, can be used.
A preparation method of an intelligent repair structure of a composite material is used for preparing the intelligent repair structure of the composite material, and comprises the following steps:
and (I) polishing the repair area of the aircraft composite material belt according to the data of the damage size and the damage depth of the surface of the aircraft composite material structure to form a groove to-be-repaired area.
And step two, cutting the sheet-shaped carbon fiber cloth 3, the epoxy resin film 1 and the epoxy resin and carbon black composite film 2 according to the size of the area to be repaired of the groove.
And step three, determining the number of layers and the layer direction of the carbon fiber sheets according to the depth of the to-be-repaired area of the groove, and performing layer paving according to the layer paving mode that the first layer is an epoxy resin film 1, the second layer is a carbon fiber cloth 3, the third layer is an epoxy resin film 1, the fourth layer is an epoxy resin and carbon black composite film 2, the fifth layer is an epoxy resin film 1, the sixth layer is a carbon fiber cloth 3 and the seventh layer is an epoxy resin film 1. The number of layers of the epoxy resin and carbon black composite film 2 can be determined according to the thickness of the composite material intelligent repair structure.
And (IV) after the layering is completed, coating the layering by using a hot-pressing vacuum bag, vacuumizing by using a vacuum pump, discharging air, heating by using a resin film infiltration process to melt and impregnate the epoxy resin film 1 and the epoxy resin and carbon black composite film 2, and solidifying and molding the intelligent repairing structure of the composite material after a certain time.
The epoxy resin film 1 adopts E51 type epoxy resin, the curing agent adopts high-temperature curing agent boron trifluoride monoethylamine, and the solvent adopts ethylene glycol.
The E51 type epoxy resin is selected as the epoxy resin film 1 because of good adhesion, high strength and insulation properties, especially the insulation property, and has important effect on realizing health detection.
The epoxy resin film 1 adopts the high-temperature curing agent boron trifluoride monoethylamine because the curing agent does not react with the epoxy resin at a lower temperature, and the curing is realized at a higher speed at a higher temperature. Thus, this catalytic curing property of boron trifluoride monoethylamine to epoxy resin provides an operating window period for the preparation of the epoxy resin film, facilitating the preparation of the epoxy resin film 1.
Further, the preparation process of the epoxy resin film 1 is as follows:
and (A) weighing a proper amount of epoxy resin in a beaker, adding glycol according to a mass ratio of 1:10, and fully stirring, diluting and dissolving.
And (B) weighing a proper amount of boron trifluoride monoethylamine in a beaker according to the required mass fraction of 0.5-1%, and adding glycol according to the mass ratio of 1:5 for fully stirring, diluting and dissolving.
And (C) mixing the dissolved boron trifluoride monoethylamine solution with epoxy resin solution, and then carrying out ultrasonic oscillation for 30min in a room temperature environment to fully mix the boron trifluoride monoethylamine curing agent with the epoxy resin.
And (D) placing the mixed epoxy resin and the boron trifluoride monoethylamine solution in a vacuum oven at 100-140 ℃ for 2h for prepolymerization.
And (E) taking out the epoxy resin after the pre-polymerization treatment in a vacuum oven, and scraping the epoxy resin film 1 with a certain thickness by using a special cutter.
The epoxy resin and carbon black composite film 2 adopts E51 type epoxy resin, conductive carbon black powder, a curing agent adopts high-temperature curing agent boron trifluoride monoethylamine, and a solvent adopts ethylene glycol.
The E51 type epoxy resin is selected as the epoxy resin and carbon black composite film 2 because of good adhesion, high strength and other performances. The matrix component of the epoxy resin and carbon black composite film is epoxy resin, and the chemical property of the epoxy resin is not changed, so that the interface of the epoxy resin, the carbon black composite film and the epoxy resin film still can generate crosslinking curing reaction in the subsequent repair curing molding process of the composite material. After the epoxy resin and the conductive carbon black powder are mixed according to a certain proportion, the mixed epoxy resin can have certain conductivity. Meanwhile, the mixed epoxy resin still has certain toughness, and can deform in structure under the action of external force, so that the conductivity of the epoxy resin is changed, and the epoxy resin has obvious strain resistance effect, so that the structural deformation can be detected by means of the property.
Further, the preparation process of the epoxy resin and carbon black composite film 2 is as follows:
and (a) weighing a proper amount of epoxy resin in a beaker, adding glycol according to a mass ratio of 1:10, and fully stirring, diluting and dissolving.
And (b) weighing a proper amount of boron trifluoride monoethylamine in a beaker according to the mass fraction of 0.5-1%, and adding glycol according to the mass ratio of 1:5 for fully stirring, diluting and dissolving.
And (c) weighing a proper amount of conductive carbon black powder in a beaker according to the mass fraction of 0.5% -2%, adding ethylene glycol according to the mass ratio of 1:100, and oscillating for 30min by using ultrasound to fully dissolve.
And (d) mixing the conductive carbon black solution with the epoxy resin solution, and then performing ultrasonic vibration for 1-2h in a room temperature environment.
And (e) pouring the dissolved boron trifluoride monoethylamine solution into the mixed solution of the epoxy resin and the carbon black, and then carrying out ultrasonic oscillation for 30min in a room temperature environment to fully mix the boron trifluoride monoethylamine curing agent, the epoxy resin and the carbon black.
And (f) pouring the mixed solution of the epoxy resin, the boron trifluoride monoethylamine and the carbon black into a corresponding cavity of a special mold, pouring the mixed solution of the epoxy resin and the boron trifluoride monoethylamine into other cavities, and placing the cavities in a vacuum oven at 100-140 ℃ for prepolymerization for 30min.
As shown in fig. 2, a schematic diagram of a mold for preparing the composite film 2 of epoxy resin and carbon black is shown, the mold mainly comprises two chambers, namely a composite film chamber 4 of epoxy resin and carbon black and an epoxy resin chamber 5, wherein the composite film chamber 4 of epoxy resin and carbon black and the epoxy resin chamber 5 are divided by a chamber dividing baffle 6. The epoxy resin cavity 5 is filled with a mixture of epoxy resin and a curing agent, and the epoxy resin and carbon black composite film cavity 4 is filled with a mixture of epoxy resin, a curing agent and carbon black.
And (g) taking out the die from the vacuum oven, rapidly drawing out a cavity dividing baffle 6 between the epoxy resin and carbon black composite film cavity 4 and the epoxy resin cavity 5, and then putting the die back into the vacuum oven again for prepolymerization for 1.5h at 100-140 ℃. The epoxy resin and the epoxy resin in the mixture of the epoxy resin and the carbon black can continue to undergo polymerization reaction, so that the interface between the epoxy resin and the carbon black has stronger bonding strength.
And (h) taking out the epoxy resin and carbon black composite after the pre-polymerization treatment in the vacuum oven, and scraping the epoxy resin and carbon black composite film 2 with a certain thickness by using a special cutter.
As shown in fig. 3, the structure of the prepared epoxy resin and carbon black composite film 2 is schematically shown. The epoxy resin and carbon black composite film 2 comprises an insulating matrix 7 and an epoxy resin and carbon black composite film sensing element 8. Wherein, the insulating matrix 7 is prepared by mixing epoxy resin and a high-temperature curing agent. The epoxy resin and carbon black composite film sensing element 8 is prepared by mixing epoxy resin, a high-temperature curing agent and carbon black according to a mass ratio of 100:1:2.
Monitoring points are arranged on the epoxy resin and carbon black composite film sensing element 8 and distributed along the directions of 0 degree, 90 degrees and 135 degrees correspondingly, and the main strain and the main direction of deformation of the corresponding measuring points can be detected. Meanwhile, the epoxy resin and carbon black composite film sensing element 8 is placed at different positions and in different layer areas of the same layer in the arrangement mode, so that strain detection of each layer can be realized. The insulating matrix 7 has insulativity, so that the epoxy resin and the carbon black composite film sensing element 8 can not influence each other.
A health self-detection method for a composite material intelligent repair structure is used for detecting the composite material intelligent repair structure and comprises the following steps:
and step (S1), connecting wires corresponding to the epoxy resin and the carbon black composite film sensing element 8 in the epoxy resin and carbon black composite film 2 into a Wheatstone bridge respectively according to a 1/4 bridge connection mode.
The circuit schematic diagram is shown in fig. 4, and the strain sensing element is connected into a wheatstone bridge in a 1/4 bridge connection mode. Wherein each strain sensing element is connected with an access bridge by two very thin, high strength and conductivity wires.
It should be noted that, the composite material intelligent repair structure may be that each side point in the structure is connected to a wheatstone bridge only when the detection needs to be performed in the service period of the aircraft, and this case may be that the periodic or irregular detection may be performed. In addition, the device can be always connected with an access bridge circuit and used for detecting deformation of the composite material repairing structure caused by pneumatic load and self vibration in the real-time flight process of the aircraft, so that the real-time detection of the safety state of the aircraft structure can be realized, and early warning response can be timely carried out under abnormal conditions.
And (S2) when the composite material intelligent repair structure is deformed, the resistance of the epoxy resin and carbon black composite film sensing element 8 is changed, so that the output voltage of the Wheatstone bridge is changed, and according to the relation between the calibrated sensing element and the resistance relative change quantity, the line strain value of each monitoring point along different directions is obtained by reading the change value of the output voltage of the Wheatstone bridge.
And step (S3) utilizing the detection of the line strain values of the monitoring points in different directions to obtain the maximum main strain direction and the maximum main strain size of the monitoring points, analyzing the positions of the layers of the composite material repairing structure, which are easy to cause defects and damages, and realizing the self-detection of the structural health.
In this embodiment, let the resistances corresponding to the respective measurement points be R 0 ，R 90 And R is 135 The resistance of the compensation sheet is R, and the power supply voltage is E. The measuring points deform under the action of external load, and the corresponding strains in all directions of the strain gauge are assumed to be epsilon respectively 0 ，ε 90 And epsilon 135 。
The relation between the output voltage and the strain of the circuit can be obtained by adopting a 1/4 bridge group bridge mode:
wherein E is the power supply voltage of a Wheatstone bridge; k is the sensitivity coefficient of the sensing element, and is obtained through a calibration experiment; epsilon is a line strain value of the monitoring point along the axis direction of the sensing element; u (U) out And outputs a voltage for the bridge.
The calibration experiment can be used for preparing a uniaxial tensile test piece by mixing the epoxy resin and the carbon black, and the sensitivity coefficient of the sensing element prepared by mixing the epoxy resin and the carbon black can be obtained by testing the strain value and the relative variation of the resistance value of the structural resistance under the action of given different tensile loads and fitting the relation between the relative variation of the resistance and the strain value.
After the calibration experiment is completed, the corresponding strain value can be obtained by reading the output voltage in the circuit.
From knowledge of elastomechanics, a point of strain along a certain direction satisfies:
ε＝ε x cos 2 θ+γ xy sinθcosθ+ε y sin 2 θ
it is possible to obtain a relationship between strain at a point in different directions and strain at a line in different directions that satisfies:
the magnitude and direction of the principal strain at this point is so as to:
therefore, the maximum principal strain and the minimum principal strain of the deformation point and the corresponding directions can be solved by testing the strain values of the point along 0 degrees, 90 degrees and 135 degrees.
Therefore, the maximum main strain direction and the maximum main strain size of the monitoring points can be obtained by detecting the line strain values of the monitoring points in different directions, so that the positions, where defects and damages easily occur, of each layer of the composite material repairing structure are analyzed, and meanwhile, the maximum main strain of each layer can be detected, and the deformation state of each layer of the structure is detected. In addition, if the composite material repairing structure has damage defects such as layering and debonding, the layer from the surface to the layering region can be approximately regarded as being subjected to bending moment acting force, and the in-plane stress change of the region below the layering interface is smaller. Therefore, the maximum main strain of the measuring point contained in the layer from the surface to the layering interface will be suddenly changed, and the maximum main strain of the measuring point below the layering interface will not be greatly changed. Therefore, the number of layers and the positions of defects generated by the composite material repair structure can be determined by testing the strain values of each point, and the health detection of the composite material repair structure is realized.
Fig. 5 is a schematic diagram of a composite intelligent repair structure, which comprises a composite patch 9 and a composite structural matrix to be repaired 10. The composite material patch 9 is adhered to the composite material structural matrix 10 to be repaired through repair or repair, so that the self-detection of the intelligent repair structural state of the composite material can be realized.
The foregoing has shown and described the basic principles, principal features and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, which is defined in the appended claims. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
1. The utility model provides a structure is repaired to combined material intelligence which characterized in that: the carbon fiber composite film comprises an epoxy resin film (1), an epoxy resin and carbon black composite film (2) and carbon fiber cloth (3), wherein the epoxy resin film (1), the epoxy resin and carbon black composite film (2) and the carbon fiber cloth (3) are paved according to a certain layering mode and are prepared by solidifying the epoxy resin film through a resin film melting and soaking process, and the epoxy resin film (1) is paved between the epoxy resin and carbon black composite film (2) and the carbon fiber cloth (3).
2. The composite intelligent repair structure according to claim 1, wherein: the certain layering mode is that the first layer is an epoxy resin film (1), the second layer is a carbon fiber cloth (3), the third layer is an epoxy resin film (1), the fourth layer is an epoxy resin and carbon black composite film (2), the fifth layer is an epoxy resin film (1), the sixth layer is a carbon fiber cloth (3), and the seventh layer is an epoxy resin film (1).
3. The composite intelligent repair structure according to claim 1, wherein: the epoxy resin and carbon black composite film (2) is formed by compounding an insulating matrix (7) and an epoxy resin and carbon black composite film sensing element (8), wherein the insulating matrix (7) is prepared by mixing epoxy resin and a high-temperature curing agent, and the carbon black composite film sensing element (8) is prepared by mixing epoxy resin, a high-temperature curing agent and carbon black.
4. A composite material intelligent repair structure according to claim 3, characterized in that: monitoring points are arranged on the carbon black composite film sensing element (8) and correspondingly distributed along the directions of 0 degree, 90 degrees and 135 degrees.
5. A preparation method of an intelligent repair structure of a composite material is characterized by comprising the following steps: a method for preparing a composite smart repair structure according to any one of claims 1 to 4, comprising the steps of:
polishing the repair area of the aircraft composite material belt according to the data of the damage size and the damage depth of the surface of the aircraft composite material structure to form a groove to-be-repaired area;
cutting a sheet-shaped carbon fiber cloth (3), an epoxy resin film (1) and an epoxy resin and carbon black composite film (2) according to the size of a to-be-repaired area of the groove;
step three, determining the number of layers and the layer direction of the carbon fiber sheet according to the depth of the to-be-repaired area of the groove, and performing layer according to a certain layer mode;
and (IV) after the layering is finished, coating the layering by using a hot-pressing vacuum bag, vacuumizing by using a vacuum pump, discharging air, heating by using a resin film infiltration process to melt and soak the epoxy resin film (1) and the epoxy resin and carbon black composite film (2), and curing and forming the intelligent repair structure of the composite material after a certain time.
6. The method for preparing the intelligent repair structure of the composite material according to claim 5, which is characterized in that: the preparation process of the epoxy resin film (1) is as follows:
weighing a proper amount of epoxy resin in a beaker, adding glycol according to a certain mass ratio, and fully stirring, diluting and dissolving;
weighing a proper amount of boron trifluoride monoethylamine in a beaker according to the required mass fraction, and adding ethylene glycol according to a certain mass proportion to fully stir, dilute and dissolve;
step (C), mixing the dissolved boron trifluoride monoethylamine solution with epoxy resin solution, and then carrying out ultrasonic oscillation for 30min in a room temperature environment to fully mix a boron trifluoride monoethylamine curing agent with epoxy resin;
step (D), placing the mixed epoxy resin and boron trifluoride monoethylamine solution in a vacuum oven at 100-140 ℃ for 2h for prepolymerization;
and (E) taking out the epoxy resin after the pre-polymerization treatment in a vacuum oven, and scraping out the epoxy resin film (1) with a certain thickness by using a special cutter.
7. The method for preparing the intelligent repair structure of the composite material according to claim 5, which is characterized in that: the preparation process of the epoxy resin and carbon black composite film (2) is as follows:
weighing a proper amount of epoxy resin in a beaker, adding glycol according to a certain mass ratio, and fully stirring, diluting and dissolving;
weighing a proper amount of boron trifluoride monoethylamine in a beaker according to the required mass fraction, and adding ethylene glycol according to a certain mass proportion to fully stir, dilute and dissolve;
step (c), weighing a proper amount of conductive carbon black powder in a beaker according to the required mass fraction, adding ethylene glycol according to a certain proportion, and oscillating for 30min by using ultrasound to fully dissolve;
step (d), mixing the conductive carbon black solution and the epoxy resin solution, and then carrying out ultrasonic vibration for 1-2h in a room temperature environment;
pouring the dissolved boron trifluoride monoethylamine solution into a mixed solution of epoxy resin and carbon black, and then carrying out ultrasonic oscillation for 30min in a room temperature environment to fully mix a boron trifluoride monoethylamine curing agent, the epoxy resin and the carbon black;
pouring the mixed solution of the epoxy resin, the boron trifluoride monoethylamine and the carbon black into a corresponding cavity of a special mold, pouring the mixed solution of the epoxy resin and the boron trifluoride monoethylamine into other cavities, and placing the cavities in a vacuum oven at 100-140 ℃ for prepolymerization for 30min;
taking out the die from the vacuum oven, rapidly drawing out the baffle plates between the chambers, and then putting the die back into the vacuum oven again to continue prepolymerization for 1.5h at 100-140 ℃;
and (h) taking out the epoxy resin and carbon black compound which are subjected to the pre-polymerization treatment in a vacuum oven, and scraping the epoxy resin and carbon black compound film (2) with a certain thickness by using a special cutter.
8. A health self-detection method of an intelligent repair structure of a composite material is characterized by comprising the following steps of: a composite smart repair structure for detecting any one of claims 1 to 4, comprising the steps of:
step (S1), connecting wires corresponding to the epoxy resin and carbon black composite film sensing element (8) in the epoxy resin and carbon black composite film (2) into a Wheatstone bridge respectively according to a 1/4 bridge connection mode;
step (S2), according to the relation between the calibrated sensing element and the relative variable quantity of the resistor, obtaining the line strain values of all monitoring points along different directions by reading the variable value of the output voltage of the Wheatstone bridge circuit;
and step (S3) utilizing the detection of the line strain values of the monitoring points in different directions to obtain the maximum main strain direction and the maximum main strain size of the monitoring points, analyzing the positions of the layers of the composite material repairing structure, which are easy to cause defects and damages, and realizing the self-detection of the structural health.
9. The method for self-testing the health of an intelligent repair structure made of composite materials according to claim 8, wherein the method comprises the following steps: in the step (S2), a strain value for repairing the structural deformation is obtained according to the wheatstone bridge output voltage:
wherein E is the power supply voltage of a Wheatstone bridge; k is the sensitivity coefficient of the sensing element, and is obtained through a calibration experiment; epsilon is a line strain value of the monitoring point along the axis direction of the sensing element; u (U) out And outputs a voltage for the bridge.
10. The method for self-testing the health of an intelligent repair structure made of composite materials according to claim 8, wherein the method comprises the following steps: in the step (S3), the maximum main strain direction and the maximum main strain size of the monitoring points can be obtained by detecting the line strain values of the monitoring points in different directions:
the point along a certain direction line strain and the point each strain satisfy the following conditions:
ε＝ε x cos 2 θ+γ xy sinθcosθ+ε y sin 2 θ
testing the linear strain of a point along three different directions (0 DEG, 90 DEG and 135 DEG), and obtaining the strain value corresponding to the detection point:
the main strain size and direction corresponding to the detection point satisfy:
the main strain magnitude and direction and strain values along 0 °,90 ° and 135 ° by testing out a point satisfy:
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