Preparation method of remodelable, recoverable and repairable carbon fiber reinforced epoxy resin-based composite material

Abstract

The invention belongs to the field of preparation of fiber reinforced resin-based composite materials, and discloses a preparation method of a remodelable, recoverable and repairable carbon fiber reinforced epoxy resin-based composite material. The preparation method comprises the following steps: (1) stirring bisphenol A diglycidyl ether and zinc acetylacetonate at 120-140 DEG C for 20-60 minutes, and reducing the temperature to 65-75 DEG C; adding glutaric anhydride, continuously stirring for 10-30 minutes, and then vacuumizing to remove bubbles, so as to obtain epoxy resin liquid; (2) brushing a release agent on the surface of a mold, cutting a carbon fiber base material, placing the cut carbon fiber base material on the mold, uniformly brushing the epoxy resin liquid on the carbon fiber base material, compacting and defoaming, and then circulating the operation for several times to obtain a carbon fiber / epoxy resin prepreg; and (3) putting the carbon fiber / epoxy resin prepreg prepared in the step (2) into a hot press along with a mold for hot pressing and curing, and cooling to room temperature to obtain a target product. The carbon fiber reinforced epoxy resin-based composite material prepared by the preparation method disclosed by the invention shows recoverable, remodeling and rapid self-repairing properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of fiber-reinforced resin-based composite materials, and in particular relates to a method for preparing a reshapeable, recyclable and repairable carbon fiber-reinforced epoxy resin-based composite material. Background Art

[0002] Carbon fiber reinforced polymer composites include thermosetting and thermoplastic materials. Thermosetting composites have many advantages in terms of strength, stiffness and flame retardancy, and are widely used in key parts such as aircraft wings, fuselages, horizontal tails and vertical tails. Thermosetting resins form a permanent chemically cross-linked network structure during curing and molding, making the integrated molding, connection, repair, degradation-recycling and remanufacturing of complex structures a global problem. Although thermoplastic composites based on physical molding have the advantages of recyclability, three-dimensional molding, high efficiency, self-connection and easy repair, they often find it difficult to meet the performance requirements of aviation structures. Therefore, the preparation of new thermosetting resins that are recyclable, reprocessable, self-connected and easy to repair, and fiber-reinforced new resin composite structural parts manufacturing technology that combine the "thermal-mechanical-chemical stability" of traditional thermosetting and "thermoplastic-like" properties are scientific problems that need to be solved urgently. Summary of the Invention

[0003] In order to solve the world problem of non-repairable, non-degradable, non-recyclable and remanufacturing of fiber-reinforced thermosetting resin composite materials, the purpose of the present invention is to provide a preparation method of reshapeable, recyclable and repairable carbon fiber reinforced epoxy resin-based composite materials To achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing a reshapeable, recyclable and repairable carbon fiber reinforced epoxy resin-based composite material, comprising the following steps: (1) Stir bisphenol A diglycidyl ether (DGEBA) and zinc acetylacetonate (Zn(Ac)2) at 120-140°C for 20-60 minutes, then reduce the temperature to 65-75°C; after the temperature stabilizes, add glutaric anhydride (GA), continue stirring for 10-30 minutes, and then vacuum to remove bubbles to obtain epoxy resin liquid; wherein, the molar ratio of the raw materials is bisphenol A diglycidyl ether: glutaric anhydride: zinc acetylacetonate = (0.7-1.3) : (0.5-0.7) : (0.03-0.05); (2) Apply a release agent on the mold surface, cut the carbon fiber substrate and place it on the mold, evenly apply the epoxy resin liquid on the carbon fiber substrate, then compact and remove bubbles, and then continue to lay the carbon fiber substrate in layers, apply the epoxy resin liquid, compact and remove bubbles, and repeat this operation several times to obtain a carbon fiber / epoxy resin prepreg; (3) Place the carbon fiber / epoxy resin prepreg prepared in step (2) together with the mold in a hot press, and carry out hot pressing and curing at a pressure of 0.5-1 MPa. First, maintain at 75-85 °C for 1-2 h, and then maintain at 155-165 °C for 2-4 h. After cooling to room temperature, the target product is obtained.

[0004] Preferably, in step (1), in terms of molar ratio, the raw material dosage ratio is bisphenol A diglycidyl ether: glutaric anhydride: zinc acetylacetonate = 1: 0.5: (0.03-0.05).

[0005] Preferably, in step (2), the carbon fiber substrate is carbon fiber unidirectional cloth or carbon fiber woven cloth.

[0006] Preferably, in step (2), each time when brushing, the dosage of the epoxy resin liquid is 30-50% of the total weight of the epoxy resin liquid + the carbon fiber substrate to be brushed.

[0007] Preferably, in step (2), the time for each compaction and defoaming is 5-10 min.

[0008] Principle of the preparation method of the present invention: The DGEBA monomer has active epoxy groups, and the catalyst Zn(Ac)2 has a catalytic effect on the epoxy ring opening. The active epoxy groups in the DGEBA monomer react with the anhydride groups in the crosslinking agent GA at high temperature to form a dynamic crosslinking network. By reasonably controlling the preparation parameters of the epoxy resin liquid, the viscosity of the epoxy resin liquid is effectively controlled below 100 Pa•s, which is beneficial to the full impregnation of the carbon fiber substrate in the later stage.

[0009] Beneficial effects: The carbon fiber reinforced epoxy resin matrix composite material prepared by the present invention has a dynamic crosslinking network, shows stress relaxation characteristics at high temperature, and exhibits recyclable, reshaping and rapid self-healing properties; the present invention reduces the raw materials, labor, equipment, and overhaul and maintenance costs in the manufacturing process of the carbon fiber resin matrix composite material, extends the service life of the parts, and at the same time reduces the energy consumption and pollutant emissions in the manufacturing process, which is of great significance to environmental protection and sustainable development. Description of the Drawings

[0010] Figure 1 : Stress relaxation curve of carbon fiber reinforced epoxy resin matrix composite material.

[0011] Figure 2 : Reshaping performance of the carbon fiber reinforced epoxy resin matrix composite material prepared in Example 1.

[0012] Figure 3 : Recycling performance of the carbon fiber reinforced epoxy resin matrix composite material prepared in Example 1.

[0013] Figure 4: Repair performance of the carbon fiber reinforced epoxy resin matrix composite prepared in Example 1. Detailed implementation manners

[0014] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present invention.

[0015] Example 1

[0016] A preparation method of a reshaping, recyclable and repairable carbon fiber reinforced epoxy resin matrix composite, comprising the following steps: (1), First, weigh DGEBA and Zn(Ac)2 according to a molar ratio of 1:0.05 and add them to a round-bottomed flask. Stir in an oil bath at 130 °C for 30 min, then lower the oil bath temperature to 75 °C; after the temperature stabilizes, add GA according to a molar ratio of DGEBA to GA of 1:0.5, and continue to stir for 30 min to form a homogeneous system. Subsequently, place the mixed liquid in a vacuum oven at 75 °C and evacuate for 15 min to remove bubbles to obtain epoxy resin liquid; (2), Brush a release agent on the surface of the mold, cut the carbon fiber unidirectional cloth with a grammage of 200 g / m 2 and place it on the mold. Weigh the epoxy resin liquid according to the proportion that the mass of the epoxy resin liquid accounts for 40% of the total mass of (epoxy resin liquid + carbon fiber unidirectional cloth). Use a brush to evenly coat the epoxy resin liquid on the carbon fiber cloth, then press and remove bubbles for 5 min. After that, continue to stack and lay the carbon fiber substrate, coat the epoxy resin liquid, and press and remove bubbles. Repeat this cyclic operation 10 times to obtain a carbon fiber / epoxy resin prepreg; (3), Place the carbon fiber / epoxy resin prepreg prepared in step (2) with the mold in a hot press. Under a pressure of 1 MPa, first heat to 80 °C and hold for 2 h, then heat to 160 °C and hold for 4 h for hot pressing and curing. After the curing is completed, take out the workpiece after the mold temperature drops to room temperature to obtain the target product.

[0017] Examples 2 to 5 The difference from Example 1 is that: in step (1), the ratios of DGEBA, GA and Zn(Ac)2 are different, that is, the molar ratio of DGEBA:GA:Zn(Ac)2 is adjusted from 1:0.5:0.05 to 1:0.5:0.01, 1:0.5:0.03, 1:0.5:0.08 and 1:0.5:0.1 in sequence, and the others are the same as in Example 1.

[0018] Example 6

[0019] The difference from Example 1 is that in step (2), the carbon fiber cloth is changed to carbon fiber woven fabric, and the others are the same as in Example 1.

[0020] Comparative Example 1 The difference from Example 1 is that in step (2), the dosage of the epoxy resin liquid is different each time of brushing, that is, in step (2), the mass ratio of the epoxy resin liquid is adjusted to 70%; the others are the same as in Example 1.

[0021] Resin content test

[0022] Table 1 shows the statistics of the resin content in the composites prepared in Example 1, Example 2, Example 3, Example 6 and Comparative Example 1. It can be seen from Table 1 that there is no obvious difference between the resin content in the composites prepared in Example 1, Example 2, Example 3 and Example 6 and the theoretical content (40%), while the difference between the resin content in the composite prepared in Comparative Example 1 and the theoretical content (70%) is relatively large. This is mainly because: the epoxy resin liquid prepared in step (1) has good fluidity at high temperature. When the mass ratio of the epoxy resin liquid in step (2) is too high, the amount of resin overflow during the curing and molding process of the material will become larger, resulting in the resin content of the final composite material not being effectively controlled.

[0023]

[0024] Performance test (I) Stress relaxation behavior test Figure 1 It is about the stress relaxation behavior (test temperature 200 °C) shown by the composites when the ratios of DGEBA, GA and Zn(Ac)2 in Examples 1 - 5 are different. From Figure 1 it can be seen that: the stress relaxation curves of DGEBA∶GA∶Zn(Ac)2 = 1∶0.5∶0.05 and 1∶0.5∶0.03 are close, while showing relatively large differences from the curves of other ratios, indicating that too high or too low content of Zn(Ac)2 cannot ensure the stress relaxation behavior of the composite material. This dynamic relaxation behavior is mainly caused by the dynamic transesterification reaction of the resin in the composite material at high temperature, which has a greater impact on the reshaping, repair and recycling performance of the composite material.

[0025] (II) Reshaping performance test The reshaping device includes an upper mold and a lower mold; the lower mold includes a first rectangular plate, and a trapezoidal groove with a wider top and a narrower bottom is provided at the middle top position of the first rectangular plate. The upper mold includes a second rectangular plate, and a trapezoidal convex block with a wider top and a narrower bottom is provided at the middle bottom position of the second rectangular plate. The sizes of the first rectangular plate and the second rectangular plate are the same, and the sizes of the trapezoidal convex block and the trapezoidal groove are adapted to ensure that when the upper mold and the lower mold are closed or opened, the trapezoidal convex block can freely enter and exit the trapezoidal groove.

[0026] Remolding process: First, keep the carbon fiber reinforced epoxy resin matrix composite at 200 °C for 30 min, then place it flat on the top of the lower mold, and use a pressing tool to apply a pressure of 5 Mpa to the upper mold for mold closing. After the sample is remolded, it is cooled to room temperature and the workpiece is taken out.

[0027] Figure 2 For the remolding results of the carbon fiber reinforced epoxy resin matrix composites in Example 1 and Example 6, the upper figure is the schematic diagram of the remolding process, and the middle figure and the lower figure are the physical photos and SEM images of the remolded workpieces respectively. In the figure, the workpiece marked with unidirectional cloth is the remolded workpiece of the carbon fiber reinforced epoxy resin matrix composite in Example 1, and the workpiece marked with woven cloth is the remolded workpiece of the carbon fiber reinforced epoxy resin matrix composite in Example 6. From Figure 2 it can be seen that: regardless of whether the fiber used is carbon fiber unidirectional cloth or carbon fiber woven cloth, the composite material can exhibit good remolding performance, and there is no obvious interlayer damage phenomenon after remolding.

[0028] (III) Recyclability test Recycling process: Immerse the carbon fiber reinforced epoxy resin matrix composite prepared in Example 1 in ethylene glycol solvent, take it out after maintaining at 220 °C for 2 h to obtain separated carbon fibers, and continue to evaporate the remaining ethylene glycol solution until the solution mass remains unchanged to obtain the recycled resin.

[0029] Figure 3 For the recyclability of the carbon fiber reinforced epoxy resin matrix composite prepared in Example 1, from Figure 3 it can be seen that: the fibers (black bottle in the right figure) and the resin (yellow bottle in the right figure, before ethylene glycol evaporation) are well separated and recycled.

[0030] (IV) Repairability test According to the standard test method for flexural properties of polymer matrix composites (D 7264-07), load the carbon fiber reinforced epoxy resin matrix composite in Example 1 until it is damaged, and then repair it. Repair process: Keep the damaged and delaminated carbon fiber reinforced epoxy resin matrix composite at 200 °C and 5 Mpa under hot pressing conditions for 2 h, cool it to room temperature and take out the workpiece to obtain the re-repaired composite workpiece.

[0031] Figure 4 For the repairability of the carbon fiber reinforced epoxy resin matrix composite in Example 1, from Figure 4 it can be seen that: the bearing performance of the repaired workpiece is close to that of the undamaged workpiece, and the repair rate reaches 92.3%.

Claims

1. A preparation method of a reshaping, recyclable and repairable carbon fiber reinforced epoxy resin matrix composite material, characterized in that, The steps are as follows: (1) Stir bisphenol A diglycidyl ether and zinc acetylacetonate at 120 - 140°C for 20 - 60 min, then lower the temperature to 65 - 75°C. After the temperature stabilizes, add glutaric anhydride and continue stirring for 10 - 30 min. Subsequently, evacuate to remove bubbles to obtain an epoxy resin solution. Among them, in terms of molar ratio, the raw material dosage ratio is bisphenol A diglycidyl ether∶glutaric anhydride∶zinc acetylacetonate = (0.7 - 1.3)∶(0.5 - 0.7)∶(0.03 - 0.05); (2) Brush a mold release agent on the surface of the mold, cut the carbon fiber substrate and place it on the mold. Uniformly brush the epoxy resin solution on the carbon fiber substrate, then compact to remove bubbles. Then continue to stack and lay the carbon fiber substrate, brush the epoxy resin solution, and compact to remove bubbles. Repeat such cyclic operations several times to obtain a carbon fiber / epoxy resin prepreg; (3) Place the carbon fiber / epoxy resin prepreg prepared in step (2) together with the mold in a hot press. First, hold at 75 - 85°C for 1 - 2 h under a pressure of 0.5 - 1 MPa, then hold at 155 - 165°C for 2 - 4 h for hot press curing. After cooling to room temperature, the target product is obtained.

2. The preparation method of the reshaping, recyclable and repairable carbon fiber reinforced epoxy resin matrix composite material according to claim 1, wherein: In step (1), in terms of molar ratio, the raw material dosage ratio is bisphenol A diglycidyl ether∶glutaric anhydride∶zinc acetylacetonate = 1∶0.5∶(0.03 - 0.05).

3. The preparation method of the reshaping, recyclable and repairable carbon fiber reinforced epoxy resin matrix composite material according to claim 1, characterized in that: In step (2), the carbon fiber substrate is carbon fiber unidirectional cloth or carbon fiber woven cloth.

4. The preparation method of the reshaping, recyclable and repairable carbon fiber reinforced epoxy resin matrix composite material according to claim 1, wherein: In step (2), each time when brushing, the dosage of the epoxy resin solution is 30 - 50% of the total weight of the epoxy resin solution + the carbon fiber substrate to be brushed.

5. The preparation method of the reshaping, recyclable and repairable carbon fiber reinforced epoxy resin matrix composite material according to claim 1, characterized in that: In step (2), the time for each compaction and defoaming is 5 - 10 min.

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