CFRP (Carbon Fiber Reinforced Plastics) girdle toughened by PA (Polyamide) non-woven fabric, mold and manufacturing method

Abstract

The invention provides a CFRP (carbon fiber reinforced plastic) girdle toughened by PA (polyamide) non-woven fabric, a mold and a manufacturing method, the CFRP girdle comprises a girdle body, the girdle body is made of a carbon fiber prepreg tape, and the fiber direction of the carbon fiber prepreg tape is consistent with the length direction of the girdle body; the toughening layer is arranged on the inner side of the annular belt body in the axial direction, and the toughening layer is made of thermoplastic polymer non-woven fabric; wherein the toughening layer and the girdle body are directly bonded through an adhesive. The CFRP girdle toughened by adopting the PA non-woven fabric is remarkably improved in the aspects of interlayer fracture toughness, impact resistance, interlayer bonding strength, static tensile property and the like, the mechanical property of the CFRP girdle is optimized by introducing the PA non-woven fabric, and higher reliability and durability are provided for application of the CFRP girdle in the fields of aerospace, bridge engineering and the like.

Description

Technical Field

[0001] The present invention relates to a CFRP belt toughened by PA non-woven fabric, a mold and a manufacturing method thereof. Background Art

[0002] Due to its high strength, low density and excellent corrosion resistance, carbon fiber reinforced composite (CFRP) has been widely used in the fields of aerospace, automotive, energy, etc. The CFRP material combines carbon fibers with a resin matrix to achieve a perfect unity of lightweight and high performance, becoming an indispensable key material in modern industry. However, although the CFRP material exhibits excellent mechanical properties under single load conditions such as tension and compression, it still faces the problem of insufficient interlaminar fracture toughness in practical applications. The insufficient interlaminar fracture toughness leads to easy delamination failure of the CFRP material under complex working conditions (such as impact, fatigue, etc.), severely limiting its application in high-performance structures.

[0003] To improve the interlaminar fracture toughness of CFRP materials, researchers have proposed various toughening techniques, mainly including matrix toughening, interface toughening and interlaminar toughening. Matrix toughening improves toughness by modifying the resin matrix (such as adding rubber particles or thermoplastic polymers), but this method often leads to a decrease in the stiffness and strength of the material. Interface toughening enhances the interfacial bonding between fibers and resin by coating nanomaterials or chemical modifiers on the surface of carbon fibers, but its process is complex and the cost is high. Interlaminar toughening improves the interlaminar fracture toughness by introducing toughening materials (such as thermoplastic films, nanofiber membranes, etc.) between CFRP layers. This method can significantly improve its delamination resistance while maintaining the overall performance of the material.

[0004] In recent years, polyamide (PA) non-woven fabric, as a new type of toughening material, has gradually attracted the attention of researchers. PA non-woven fabric has a multi-layer random fiber structure, which can form a three-dimensional interactive bonding network between CFRP layers, thus significantly enhancing the interfacial bonding between resin and carbon fibers. In addition, the toughening layer 70 has good thermal stability and mechanical properties, and can maintain the stability of its physical and chemical properties during the hot pressing process of CFRP. By introducing PA non-woven fabric between CFRP layers, not only can the interlaminar fracture toughness (G IC and G ⅡC ) of the material be effectively improved, but also its impact resistance and fatigue performance can be improved.

[0005] Although the toughening technology of PA non-woven fabric shows great application potential in CFRP materials, it still faces some challenges in practical applications. For example, the areal density, fiber distribution of PA non-woven fabric and its interfacial bonding strength with resin have significant effects on the toughening effect. How to optimize these parameters to achieve the best toughening effect still needs further research. In addition, the process adaptability, cost-effectiveness of the PA non-woven fabric toughening technology and its universality in different types of CFRP materials also need to be deeply explored.

[0006] In summary, developing a CFRP material based on PA non-woven fabric toughening and its preparation method for solving... Summary of the Invention

[0007] The present invention provides a CFRP ring tape toughened by PA non-woven fabric, a mold and a manufacturing method, which can effectively solve the above problems.

[0008] The present invention is realized as follows:

[0009] A CFRP ring tape toughened by PA non-woven fabric, comprising

[0010] A ring tape body made of carbon fiber prepreg tape, wherein the fiber direction of the carbon fiber prepreg tape is consistent with the length direction of the ring tape body;

[0011] A toughening layer provided on the inner side of the axial direction of the ring tape body, and the toughening layer is composed of a thermoplastic polymer non-woven fabric;

[0012] Wherein, the toughening layer and the ring tape body are directly bonded through an adhesive.

[0013] The beneficial effects of the present invention are:

[0014] (1) By introducing a thermoplastic polymer non-woven fabric as a toughening layer, the present invention significantly improves the interlaminar fracture toughness and delamination resistance of the CFRP ring tape. Specifically, the toughening layer and the ring tape body are directly bonded through an adhesive to form a tight interfacial bond, effectively enhancing the overall strength and toughness of the material. The porous structure and fiber bridging effect of the thermoplastic polymer non-woven fabric dissipate a large amount of energy during the crack propagation process, delaying the crack propagation speed, thereby significantly improving the impact resistance and fatigue life of the material. In addition, the introduction of the toughening layer optimizes the interlaminar bonding strength of the CFRP ring tape, making it show higher reliability and durability under complex working conditions, and is suitable for high-performance structures in the fields of aerospace, automotive and energy. Brief Description of the Drawings

[0015] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the attached drawings required for the embodiments. It should be understood that the following attached drawings only show some embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related attached drawings can also be obtained based on these attached drawings.

[0016] Figure 1 It is a schematic assembly diagram of the mold and the belt body of the present invention.

[0017] Figure 2 It is a schematic structural diagram of the substrate and the positioning member of the present invention.

[0018] Figure 3 It is a schematic structural diagram of the belt body of the present invention.

[0019] Figure 4 It is a schematic diagram of the DCB test of the CFRP plate toughened by the interlayer toughening layer of the present invention.

[0020] Figure 5 It is a schematic diagram of the ENF test of the CFRP plate toughened by the interlayer toughening layer of the present invention.

[0021] Figure 6 It is a schematic diagram of the failure mode of the CFRP plate toughened by the interlayer toughening layer of the present invention.

[0022] Figure 7 It is a schematic diagram of the interlayer cross-section of the DCB and ENF specimens of the present invention.

[0023] Figure 8 It is a schematic diagram of the DSC results of the toughening layers of different specifications of the present invention.

[0024] Figure 9 It is a schematic comparison diagram of the SEM morphologies of the cross-sections of the CFRP plates before and after toughening by the interlayer toughening layer of the present invention.

[0025] Figure 10 It is a schematic comparison diagram of the SEM morphologies of the cross-sections of the CFRP plates toughened by toughening layers with different areal densities of the present invention.

[0026] Figure 11 It is a schematic diagram of the details of the bonding between the fibers and the resin of the toughening layer of the present invention.

[0027] Figure 12 It is a three-dimensional height map of the cross-section of the CFRP plate toughened by the interlayer toughening layer of the present invention.

[0028] Figure 13 It is a load-displacement curve graph of the CFRP loop cables with different toughening methods of the present invention.

[0029] Figure 14 It is a comparison graph of the average strengths of the CFRP loop cables with different toughening methods of the present invention.

[0030] Figure 15 It is a schematic diagram of the failure mode of CFRP annular cables with different toughening methods of the present invention.

[0031] Figure 16 It is a schematic diagram of the fracture positions of CFRP annular cables before and after toughening by the interlayer toughening layer of the present invention.

[0032] Figure 17 It is a comparison diagram of the SEM morphology of the cross-sections of CFRP annular cables before and after toughening by the interlayer toughening layer of the present invention.

[0033] Figure 18 It is a detailed diagram of the combination of PA fibers and resin of the present invention.

[0034] Figure 19 It is a comparison diagram of the SEM morphology of the fracture surfaces of CFRP annular cables before and after toughening by the interlayer toughening layer of the present invention.

[0035] Figure 20 It is a SEM morphology diagram of the longitudinal cracks of CFRP annular cables toughened by the interlayer toughening layer of the present invention.

[0036] Figure 21 It is a three-dimensional height diagram of the cross-section of CFRP annular cables toughened by the interlayer toughening layer of the present invention.

[0037] Figure 22 It is a two-dimensional height diagram of the cross-section of CFRP annular cables toughened by the interlayer toughening layer of the present invention.

[0038] Explanation of the reference numerals in the drawings:

[0039] 10. Substrate; 100. Positioning block;

[0040] 20. Positioning member; 200. Positioning groove;

[0041] 30. Positioning bolt; 40. Lower mold; 50. Upper mold; 60. Annular body; 70. Toughening layer. Detailed implementation manners

[0042] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention.

[0043] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0044] Referring to Figure 1-3 as shown, a CFRP belt toughened with PA non-woven fabric includes

[0045] a belt body 60 made of carbon fiber prepreg tape, with the fiber direction of the carbon fiber prepreg tape being consistent with the length direction of the belt body 60; a toughening layer 70 provided on the inner side in the axial direction of the belt body 60, and the toughening layer 70 is composed of a thermoplastic polymer non-woven fabric; wherein, the thermoplastic polymer non-woven fabric is a polyamide non-woven fabric; wherein, the toughening layer 70 and the belt body 60 are directly bonded through an adhesive. Among them, the adhesive is an epoxy resin, a thermoplastic adhesive or a nano-material reinforced adhesive. Preferably, the adhesive is an epoxy resin.

[0046] Furthermore, the areal density of the toughening layer 70 is 15 g / m2 - 40 g / m 2 . Preferably, the areal density of the toughening layer 70 is 20 g / m 2 . Referring to the appendix Figure 4 , the mode I interlaminar fracture toughness (G IC ) of the CFRP belt was tested through a double cantilever beam test (DCB test), and the test results are as Figure 4 (a) and 4(b) shown. The following are the DCB test results and analysis;

[0047] Each load-displacement curve consists of 5 segments of loading curves, corresponding to 5 loading-unloading cycles for each specimen; among them, each loading curve can be divided into two stages: linear growth stage: the slopes of the un-toughened specimen and the toughened specimen are basically the same. As the displacement increases, the load increases linearly until the peak load is reached. Crack propagation stage: after reaching the peak load, the load starts to decrease. The peak load of the toughened specimen is significantly higher than that of the un-toughened specimen, indicating that the addition of the toughening layer 70 effectively improves the interlaminar fracture toughness. When the crack propagates to a certain length, unload and conduct the next loading; with the addition of the toughening layer 70 and the increase of its areal density, the peak load of each loading is significantly increased, and the area enclosed by the load-displacement curve also increases significantly, indicating that G IC significantly increases with the increase of the areal density of the toughening layer 70; the GIC values calculated based on the peak load and displacement of the load-displacement curve are as Figure 4 (b) shown; the G of the un-toughened specimen ICis 273.9 J / m2. After adding the toughening layer 70 (toughening layer 70), when the areal density is 15 g / m2, 20 g / m2, 30 g / m2 and 40 g / m2, G IC is respectively increased to 720.5 J / m2, 962.4 J / m2, 1336.1 J / m2 and 1577.0 J / m2, and the increase rates are 163%, 251%, 388% and 476% respectively; the mode II interlaminar fracture toughness (G ⅡC ) of the CFRP belt was tested by the end notched flexure test (ENF test), and the test results are as shown in Figure 5 (a) and 5(b). The following is a detailed analysis of the test results:

[0048] Each load-displacement curve consists of 5 loading curves, corresponding to 5 loading-unloading cycles for each specimen. Among them, each loading curve can be divided into two stages: linear growth stage: the slopes of the un-toughened specimen and the toughened specimen are basically the same. As the displacement increases, the load increases linearly until the peak load is reached; crack propagation stage: after reaching the peak load, the load begins to decrease. The peak load of the toughened specimen is significantly higher than that of the un-toughened specimen, indicating that the addition of the toughening layer 70 effectively improves the interlaminar fracture toughness. When the crack propagates to a certain length, unload and perform the next loading; with the addition of the toughening layer 70 and the increase of its areal density, the peak load of each loading is significantly increased, and the area enclosed by the load-displacement curve also increases significantly, indicating that G ⅡC significantly increases with the increase of the areal density of the toughening layer 70; the G ⅡC values calculated according to the peak load and displacement of the load-displacement curve are as shown in Figure 5 (b). The G ⅡC of the un-toughened specimen is 758.4 J / m2. After adding the toughening layer 70 (toughening layer 70), when the areal density is 15 g / m2, 20 g / m2, 30 g / m2 and 40 g / m2, G ⅡC is respectively increased to 1868.9 J / m2, 2038.6 J / m2, 2307.4 J / m2 and 2302.1 J / m2, and the increase rates are 146%, 169%, 204% and 204% respectively.

[0049] Furthermore, as shown in Figure 6 , there are various different failure phenomena in the toughening of the interlaminar toughening layer 70 (PA non-woven fabric). In the DCB test, each specimen is delaminated. It is worth noting that the phenomenon of bridging occurs in the PA interlaminar toughened specimen. When the specimen is subjected to a vertical tensile load, the fiber filaments of the toughening layer 70 form a bridging effect between the layers, resisting the vertical tensile load and improving G IC, in the ENF test, the PA-30 and PA-40 specimens showed flexural failure, and the rest of the specimens showed delamination failure. This is because as the areal density of the toughening layer 70 increases, G ⅡC gradually increases. When the areal density is 30 g / m 2 and 40 g / m 2 , G ⅡC continues to increase, making the load required for delamination failure greater than the load required for flexural failure, and the specimens showed flexural failure before delamination failure. Therefore, the interlaminar crack did not propagate after the specimens failed, and indentations corresponding to flexural failure appeared on the specimen surface. The measured ultimate loads and ultimate displacements of the PA-30 and PA-40 test groups were almost the same, and both were curves corresponding to flexural failure. The actual G ⅡC of the PA-30 and PA-40 test groups was greater than the measured 2307.4 J / m 2 and 2302.1 J / m 2 . Further, as shown in Figure 7 , the cross-section of the un-toughened specimen of the DCB and ENF specimens was relatively smooth. Some fibers of the ENF specimen were torn, indicating that the crack propagation path was relatively single and the interfacial bonding between the fiber and the resin was weak. In contrast, obvious white toughening layer 70 could be seen in the cross-section of the toughened specimen, and the toughening layer 70 was well bonded to the fiber surface. As the areal density of the toughening layer 70 increased, the fiber area torn together with the toughening layer 70 after failure increased significantly, indicating that the interfacial bonding effect between the toughening layer 70, the fiber and the epoxy resin gradually increased.

[0050] In summary, in the experiment of toughening CFRP plates with interlaminar carbon nanotubes, taking the areal density (15 g / m2, 20 g / m2, 30 g / m2 and 40 g / m2) of the toughening layer 70 as the independent variable, through DCB and ENF tests, the improvement effect on the mode I and mode II interlaminar fracture toughness was evaluated. Combining thermal property analysis, optical property analysis and microscopic morphology analysis, the toughening mechanism was deeply studied. The main conclusions are as follows:

[0051] The interlaminar fracture toughness increased significantly with the increase of the areal density. When the areal density was 15 g / m2, 20 g / m2, 30 g / m2 and 40 g / m2, GIC increased by 163%, 251%, 388% and 476% respectively, and G ⅡC increased by 146%, 169%, 204% and 204% respectively. When the areal density was 30 g / m2 and 40 g / m2, the ENF specimens showed flexural failure before delamination failure. With the increase of the areal density, resin loss occurred during the hot pressing process. Therefore, there is an optimal areal density that makes the interlaminar fracture toughness reach the maximum value. In this experiment, when the areal density was 20 g / m2, the toughening effect was the best.

[0052] To verify that the toughening layer 70 with a surface density of 2020 mg / m 2 has the best toughening effect, the results of differential scanning calorimetry (DSC) analysis of toughening layers 70 with different surface densities in this case are shown in the attached Figure 8 as follows:

[0053] It can be seen from the heating and cooling curves that the toughening layer 70 shows an obvious melting peak near 220°C and a crystallization exothermic peak is detected near 180°C. Through the calculation of the key parameters of the DSC curve, it is found that the toughening layer 70 with different surface densities has little change in terms of glass transition temperature, melting temperature, crystallization temperature and crystallinity, indicating that the toughening layer 70 exhibits excellent thermal stability under various surface density conditions; the thermal stability of the toughening layer 70 is crucial for the preparation of CFRP plates. Since the forming temperature of the hot pressing process of CFRP plates is 168°C, the toughening layer 70 can maintain the stability of its physical and chemical properties at this temperature, avoiding the occurrence of degradation or other thermal failure phenomena, thus ensuring that it fully plays its strengthening role during the forming process. This thermal stability not only improves the preparation quality of CFRP plates, but also optimizes their overall performance, providing a reliable guarantee for practical applications.

[0054] Under microscopic damage detection, referring to Figure 9 , before toughening (the leftmost one), bare carbon fibers can be clearly seen on the cross-section, some carbon fibers are broken, and the surface of the carbon fibers is smooth, indicating that the interfacial bonding between the carbon fibers and the resin is weak, and crack propagation mainly occurs along the fiber-resin interface. In the cross-sections after toughening (the second, third and fourth from the right), the carbon fibers are covered by resin and PA fibers, and almost no bare carbon fibers can be seen, indicating that the addition of the toughening layer 70 significantly enhances the interfacial bonding between the resin and the carbon fibers, and the crack propagation path transfers from the fiber-resin interface to the interlayer resin region. Further observing the PA fibers, it is found that some PA fibers remain intact, some are broken, and some PA fibers are pulled out, leaving a fibrous depression area on the resin surface. This indicates that the toughening layer 70 forms an effective bridging effect in the interlayer resin, which can prevent crack propagation. When the crack propagates, it is necessary to pull out or break the PA fibers between the resins, and this process dissipates a large amount of energy, thus significantly improving the interlayer fracture toughness of the material.

[0055] Furthermore, referring to Figure 10, This figure shows the SEM images of the cross-section of the CFRP plate toughened by the toughening layer 70 with different areal densities (from left to right, the densities are 15 g / m2, 20 g / m2, 30 g / m2, and 40 g / m2 respectively). As the areal density of the toughening layer 70 increases, the number of PA fibers in the image significantly increases. When the areal density is 15 g / m2 and 20 g / m2, the PA fibers on the cross-section surface are complete, plump, and evenly distributed; while when the areal density increases to 30 g / m2 and 40 g / m2, the PA fibers show signs of extrusion deformation. This is because the number of PA fibers between layers increases, and the fibers squeeze each other, causing some fibers to deform during the hot pressing process. At the same time, the increase in PA fibers between layers occupies the space of the resin, resulting in some resin being extruded, which weakens the interlayer strength to a certain extent. Therefore, the increase in the areal density of the toughening layer 70 does not linearly increase the interlayer fracture toughness, but there is an optimal value. Beyond this value, the toughening effect may tend to saturate or even decrease.

[0056] Refer to Figure 11 , By observing the bonding details between PA fibers and resin, it can be found that an interactive bonding effect is formed between PA fibers and resin. The toughening layer 70 is a porous structure material composed of multiple layers of randomly intertwined PA fibers. When the toughening layer 70 is added to the interlayer of the CFRP plate, the resin flows and fills the pores of the PA fibers during the curing process and binds tightly with the PA fibers. At the same time, the same PA fiber shuttles between different resin layers, forming a three-dimensional interactive bonding effect with the resin. This structure significantly enhances the bridging effect, thereby improving the interlayer fracture toughness. As the areal density of the toughening layer 70 increases, the number of PA fiber layers increases, further enhancing the interactive bonding effect between PA fibers and resin. Therefore, the interlayer fracture toughness increases significantly with the increase in the areal density of the toughening layer 70, but when the areal density is too high, fiber extrusion and resin loss may cause the toughening effect to tend to saturate.

[0057] Exhibit Figure 12 (Three-dimensional height map), The interlayer fracture surface of the CFRP plate toughened by the toughening layer 70 with different areal densities was observed by a white light interferometer. The results show that after adding the toughening layer 70, PA fibers are clearly visible on the fracture surface, and the undulation degree of the cross-section significantly increases, indicating that the crack propagation path is more complex. The following table lists the calculated roughness parameters. Compared with the non-toughened specimen, both Sa and Sq increase after adding the toughening layer 70, and as the areal density of the toughening layer 70 increases, Sa and Sq further increase. This phenomenon indicates that the addition of the toughening layer 70 significantly increases the tortuosity of the crack propagation path, thereby enhancing the interlayer fracture toughness. And the following table is the cross-section roughness of the CFRP plate toughened by the interlayer toughening layer 70;

[0058] Group Control PA-15 PA-20 PA-30 PA-40 Sa (μm) 5.26 20.15 24.52 25.60 27.15 Sq (μm) 6.28 30.15 35.10 34.89 38.43

[0059] In summary, with the increase of areal density, resin loss occurs during the hot pressing process. There is an optimal areal density that maximizes the interlaminar fracture toughness. In this experiment, the areal density of 20 g / m2 is the optimal areal density, which maximizes the interlaminar fracture toughness. The toughening layer 70 in the interlayer significantly improves the energy dissipation capacity through the interaction between PA fibers and resin, making the crack propagation path more complex and significantly increasing the fracture surface roughness. The microscopic morphology analysis further verifies the energy dissipation mechanism formed by the toughening material in the interlayer, delaying the crack propagation and enhancing the interlaminar fracture toughness.

[0060] Furthermore, based on the research results of the toughening effect of the above CFRP plates, applying the optimal parameters, the areal density of the toughening layer 70 in the interlayer is 20 g / m2, and a static tensile test is carried out. At the same time, two other toughening methods (matrix carbon nanotube toughening and interlayer carbon nanotube toughening) are set for comparison. Specifically, the carbon nanotube concentration of the matrix carbon nanotube toughening is 0.8 wt%, and the areal density of the carbon nanotubes of the interlayer carbon nanotube toughening is 18 mg / m 2 , the effects of different toughening methods on the tensile properties of CFRP hoop cables are studied, and the failure modes and microscopic toughening mechanisms are analyzed. The load-displacement curve of the static tensile test of the CFRP hoop cable is as Figure 13 shown. In the initial stage of loading, the load increases linearly with displacement, and the interlayer performance of the hoop cable is good without delamination failure. When the load reaches a certain value, it enters the delamination initiation stage, and the load value drops suddenly, indicating that the hoop cable begins to have interlayer failure. At this time, the slope of the curve remains the same as before delamination, indicating that the hoop cable only has interlayer failure without in-layer failure, and the stiffness remains unchanged. As the load continues to increase, the hoop cable enters the delamination propagation stage. With the expansion of delamination, the hoop cable has in-layer failure, and finally the whole cable undergoes brittle failure and loses its load-bearing capacity. By calculating the delamination strength and ultimate strength of the CFRP hoop cable, as Figure 14 shown, it is found that the average delamination strength and ultimate strength of the hoop cable under matrix carbon nanotube toughening and interlayer carbon nanotube toughening both decrease. Specifically, the average delamination strength of the hoop cable under matrix carbon nanotube toughening decreases by 16%, and the average ultimate strength decreases by 6%. The average delamination strength of the hoop cable under interlayer carbon nanotube toughening decreases by 12%, and the average ultimate strength decreases by 2%. In contrast, the average delamination strength and ultimate strength of the hoop cable under the toughening of the interlayer toughening layer 70 increase by 13% and 7% respectively. This shows that adding carbon nanotubes to the matrix and interlayer will both lead to a decrease in the interlayer performance of the hoop cable, while adding the toughening layer 70 to the interlayer can effectively improve the interlayer performance.

[0061] Furthermore, referring to Figure 15, the failure mode of the specimens further verified the above conclusions. After the brittle failure occurred locally in the annular cables without toughening, toughened with matrix carbon nanotubes, and toughened with interlayer carbon nanotubes, overall failure occurred. After failure, the annular cables were in strip shapes. It was observed that the width of most strips of the annular cables without toughening after failure was 2 - 5 mm, and the width of a few strips was less than 2 mm; while the width of the strips of the annular cables toughened with matrix carbon nanotubes and interlayer carbon nanotubes after failure was less than 2 mm, indicating that after adding carbon nanotubes to the matrix or interlayer, the integrity of the annular cables decreased. After adding the toughening layer 70 to the interlayer, only local brittle failure occurred in the annular cables, and the other parts of the annular cables remained intact with a width still of 12 mm, and the integrity was significantly improved. Refer to Figure 16 , observe the fracture positions of the annular cables before and after toughening with the interlayer toughening layer 70. Among them, (a) - (c) are the detailed diagrams of the fracture positions of the annular cables before toughening, and the fracture positions are at the intersection of the straight and curved parts. (d) - (f) are the detailed diagrams of the fracture positions of the annular cables after toughening, and the fracture positions are transferred to the lap joint of the straight line segments.

[0062] To further verify the toughening effect of the toughening layer 70, refer to the following table:

[0063]

[0064]

[0065] The above table lists the delamination strength (f d ) and ultimate strength (f u ) of all valid specimens. By calculating the ratio of the delamination strength to the ultimate strength (f d / f u ), it was found that f d / f u decreased under toughening with matrix carbon nanotubes and interlayer carbon nanotubes, while f d / f u increased under toughening with the interlayer toughening layer 70. It should be noted that the f d / f u of the Strap - PA - 2 specimen reached 100%, indicating that no delamination occurred in the annular cable before failure. This result shows that by optimizing the manufacturing process of the CFRP annular cable toughened with the interlayer toughening layer 70, it is expected to completely avoid the delamination problem of the CFRP annular cable, providing an important reference for the performance optimization of the annular cable.

[0066] Furthermore, the SEM images of the cross - sections of the CFRP annular cables before and after toughening with the interlayer toughening layer 70 are as Figure 17As shown, before toughening, carbon fibers were exposed on the fracture surface, and some carbon fibers were fractured. A small amount of resin remained on the surface of the carbon fibers, indicating a weak interfacial bond between the carbon fibers and the resin. The crack propagation mainly occurred along the fiber-resin interface. Further observation revealed that the arrangement direction of the residual resin was approximately 45° to the fiber direction, indicating that the interlaminar failure behavior of the CFRP hoop cable was a mixed mode of opening type (type I) and sliding shear type (type II). In the cross-section after toughening, the addition of the toughening layer 70 significantly enhanced the interfacial bonding between the resin and the carbon fibers, and the crack propagation path shifted from the fiber-resin interface to the interlaminar resin region. Consistent with the cross-section results of the CFRP plate, the PA fibers formed an effective bridging effect in the interlaminar resin. When the crack propagated, it was necessary to pull out or break the PA fibers between the resins, and this process dissipated a large amount of energy, thus significantly improving the interlaminar fracture toughness of the material. Further, referring to Figure 18 , an interactive bonding effect was formed between the A fibers and the resin. The multi-layer irregular fiber structure of the toughening layer 70 allowed the resin to fill its pores during the curing process and tightly bond with the PA fibers. The same PA fiber shuttled between different resin layers, forming a three-dimensional interactive bonding network, significantly enhancing the bridging effect, and thus improving the interlaminar fracture toughness. This phenomenon was consistent with the toughening results of the CFRP plate, indicating that the toughening mechanism of the toughening layer 70 in the CFRP hoop cable was the same as that in the CFRP plate, further verifying the effectiveness of the toughening layer 70 in the interlaminar toughening of the CFRP hoop cable.

[0067] Referring to Figure 19 , it is the SEM morphology diagram of the fracture of the CFRP hoop cable. Before toughening, the interval between layers at the fracture was large, the interlaminar bonding effect was poor, and obvious separation occurred between layers, indicating that the hoop cable was prone to delamination failure during the loading process. After toughening, the first, second, and third layers of fibers were still tightly bonded after the failure of the hoop cable, and there was no obvious separation between layers, indicating that the toughening layer 70 played a significant strengthening role between layers. The toughening layer 70 formed a three-dimensional interactive bonding network with the resin through its multi-layer irregular fiber structure, enhancing the interlaminar bonding force. At the same time, the crack propagation was delayed through the fiber bridging effect, significantly improving the integrity and delamination resistance of the hoop cable. Observing the longitudinal crack formed after the failure of the toughened specimen, the SEM image is as Figure 20 shown. In the longitudinal crack, a large number of PA fibers perpendicular to the crack direction can be seen connecting the hoop cables at both ends of the crack. This phenomenon indicates that the toughening layer 70 can not only improve the interlaminar bonding effect but also enhance the bonding strength perpendicular to the carbon fiber direction within the layer, improving the integrity of the hoop cable from multiple dimensions.

[0068] Referring to Figure 21(Three-dimensional height map). The interlaminar fracture surfaces of the CFRP hoop cable before and after toughening of the interlayer toughening layer 70 were observed by a white light interferometer. The results showed that PA fibers were clearly visible on the fracture surface after toughening, the degree of undulation of the cross-section increased significantly, and the crack propagation path became more complex. The following table lists the calculated roughness parameters. Compared with the specimens without toughening, both Sa and Sq increased significantly after adding the toughening layer 70. This phenomenon indicates that the introduction of the toughening layer 70 significantly increases the complexity of the crack propagation path, thereby improving the interlaminar fracture toughness.

[0069] Group Strap-Control Strap-PA Sa (μm) 12.78 20.45 Sq (μm) 15.15 28.58

[0070] In summary, through microstructure analysis, the toughening effect of the toughening layer 70 on the interlaminar fracture toughness of the CFRP hoop cable was systematically studied. The results show that the introduction of the toughening layer 70 significantly enhances the interfacial bonding between the resin and carbon fibers, forms a multi-layer random fiber structure, and constructs a three-dimensional interactive bonding network with the resin and carbon fibers. This structure not only increases the complexity of the crack propagation path but also dissipates a large amount of energy through fiber bridging, thereby significantly improving the interlaminar fracture toughness of the material. In addition, the toughened CFRP hoop cable shows higher in-plane bonding strength in longitudinal cracks, further improving the overall performance. The observation results of the white light interferometer show that the degree of undulation of the fracture surface after toughening increases significantly, and the roughness parameters (Sa and Sq) increase significantly, further verifying the effect of the toughening layer 70 on complicating the crack propagation path. At the same time, through the research and experimental verification of this case, the carbon fiber reinforced composite (CFRP) hoop toughened with polyamide (PA) non-woven fabric shows significant beneficial effects in terms of mechanical properties and interlaminar fracture toughness.

[0071] The following are the main advantages and data support for the toughening of the toughening layer 70:

[0072] (1) Significant improvement in interlaminar fracture toughness:

[0073] Through double cantilever beam test (DCB) and end notched flexure test (ENF), the CFRP hoop toughened with the toughening layer 70 has significant improvements in mode I and mode II interlaminar fracture toughness (G IC and G ⅡC ). When the areal density of the toughening layer 70 is 20 g / m2, G IC increases from 273.9 J / m 2 to 962.4 J / m 2 , an increase of 251%; G ⅡC increases from 758.4 J / m 2 to 2038.6 J / m 2 , an increase of 169%. This indicates that the toughening layer 70 forms an effective bridging effect between layers, significantly delaying the crack propagation;

[0074] (2) Improvement in impact resistance:

[0075] The introduction of the toughening layer 70 significantly enhances the impact resistance of the CFRP band. Especially during the crack propagation process, the bridging effect of the PA fibers effectively delays the crack propagation and improves the overall toughness of the material;

[0076] (3) Enhancement of interlaminar bonding strength:

[0077] Through microstructure analysis, the toughening layer 70 forms a three-dimensional interactive bonding network with the resin and carbon fibers, significantly enhancing the interlaminar bonding strength. The toughened CFRP band shows higher in-plane bonding strength in longitudinal cracks, further improving the overall performance;

[0078] (4) Optimization of static tensile properties:

[0079] In the static tensile test, the CFRP band toughened by the toughening layer 70 shows higher delamination strength and ultimate strength. Compared with the untoughened band, the delamination strength of the PA-toughened band is increased by 13%, and the ultimate strength is increased by 7%. It is worth noting that no delamination occurs in the PA-toughened band before failure, indicating that by optimizing the toughening process of the toughening layer 70, the delamination problem of the CFRP band can be completely avoided;

[0080] (5) Thermal stability and process adaptability:

[0081] The toughening layer 70 shows excellent thermal stability during the hot pressing process of the CFRP band, ensuring that it will not degrade or suffer other thermal failure phenomena during the high-temperature forming process, thus guaranteeing the preparation quality and overall performance of the CFRP band.

[0082] In summary, the CFRP band toughened by the toughening layer 70 shows significant improvements in interlaminar fracture toughness, impact resistance, interlaminar bonding strength, and static tensile properties. The introduction of the toughening layer 70 not only optimizes the mechanical properties of the CFRP band but also provides higher reliability and durability for its applications in aerospace, bridge engineering, and other fields.

[0083] A mold for manufacturing a CFRP belt, comprising a substrate 10, a positioning block 100 arranged on the top of the substrate 10, positioning members 20 symmetrically arranged on the top of the substrate 10 and on the adjacent side of the positioning block 100, a positioning groove 200 formed on the positioning member 20, and a plurality of positioning bolts 30 symmetrically arranged on the top of the substrate 10; a mold made of an upper mold 40 and a lower mold 50 is inserted into the middle of the positioning groove 200, wherein an annular belt body 60 is sleeved on the lower mold 50, and a release agent is coated on the inner surface of the mold to prevent the annular belt body 60 from adhering to the mold; it also includes a heating device and a pressure device (existing structure), wherein the heating device is used to provide a constant temperature of 168 °C during the forming process of the annular belt body 60, and the pressure device is used to apply uniform pressure during the hot pressing forming process to ensure the tight bonding between the toughening layer 70 and the annular belt body 60.

[0084] A preparation method for manufacturing a CFRP belt, comprising the following steps:

[0085] S1. Prepare a carbon fiber prepreg to ensure that the fiber direction is consistent with the length direction of the annular belt body 30;

[0086] S2. Lay a polyamide non-woven fabric on the inner side of the annular belt body 60 as the toughening layer 70, with a surface density of 15 g / m2 - 40 g / m 2 ;

[0087] S3. Place the laid annular belt body 60 and toughening layer 70 into the mold, and through the hot pressing forming process, directly bond the paired toughening layer 70 and the annular belt body 60 by using the epoxy resin on the surface of the prepreg;

[0088] S4. Through the heating device, cure the annular belt body 60 and the toughening layer 70 at a forming temperature of 168 °C to ensure the thermal stability of the toughening layer 70;

[0089] S5. Demold after cooling to obtain the final CFRP belt.

[0090] The pressure applied by the pressure device is 0.5 - 1.0 MPa, and the heating and curing time of the heating device is 60 - 90 minutes.

[0091] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A CFRP belt toughened with PA non-woven fabric, characterized in that, Comprising An annular belt body (60) made of a carbon fiber prepreg tape, wherein the fiber direction of the carbon fiber prepreg tape is consistent with the length direction of the annular belt body (60); A toughening layer (70) disposed on the inner side in the axial direction of the annular belt body (60), and the toughening layer (70) is composed of a thermoplastic polymer non-woven fabric; Wherein, the toughening layer (70) is directly bonded to the annular belt body (60) through an adhesive.

2. The CFRP belt toughened by PA non-woven fabric according to claim 1, wherein The thermoplastic polymer non-woven fabric is a polyamide non-woven fabric.

3. The CFRP belt toughened with PA non-woven fabric according to claim 1, wherein The areal density of the toughening layer (70) is 15 g / m2 - 40 g / m2.

4. A CFRP belt toughened with PA non-woven fabric according to claim 1, characterized in that The adhesive is an epoxy resin, a thermoplastic adhesive or a nano-material enhanced adhesive.

5. A CFRP belt toughened with PA non-woven fabric according to claim 4, characterized in that, The adhesive is an epoxy resin.

6. A mold for manufacturing the CFRP belt according to any one of claims 1-5, characterized in that, Comprising a substrate (10), a positioning block (100) disposed on the top of the substrate (10), positioning members (20) symmetrically disposed on the top of the substrate (10) and adjacent to one side of the positioning block (100), a positioning groove (200) formed on the positioning members (20), and a plurality of positioning bolts (30) symmetrically disposed on the top of the substrate (10).

7. The mold according to claim 6, characterized in that, A mold made of an upper mold (40) and a lower mold (50) is inserted into the middle of the positioning groove (200), wherein the annular belt body (60) is sleeved on the lower mold (50), and a release agent is coated on the inner surface of the mold to prevent the annular belt body (60) from adhering to the mold.

8. The mold according to claim 6, characterized in that, Further comprising a heating device and a pressure device, wherein the heating device is used to provide a constant temperature of 168 °C during the forming process of the annular belt body (60), and the pressure device is used to apply a uniform pressure during the hot pressing forming process to ensure the tight bonding between the toughening layer (70) and the annular belt body (60).

9. A preparation method for manufacturing the CFRP belt according to any one of claims 1-6, characterized in that, Comprising the following steps: S1. Prepare a carbon fiber prepreg tape to ensure that the fiber direction is consistent with the length direction of the annular belt body (60); S2. Lay a polyamide non-woven fabric on the inner side of the annular belt body (60) as the toughening layer (70), with an areal density of 15 g / m2 - 40 g / m2; S3. Place the laid annular belt body (60) and the toughening layer (70) into a mold, and directly bond the toughening layer (70) to the annular belt body (60) by using the epoxy resin on the surface of the prepreg through a hot pressing forming process; S4. Cure the annular belt body (60) and the toughening layer (70) at a forming temperature of 168 °C through the heating device to ensure the thermal stability of the toughening layer (70); S5. Demold after cooling to obtain the final CFRP annular belt.

10. The method according to claim 9, characterized in that, The pressure applied by the pressure device is 0.5 - 1.0 MPa, and the heating and curing time of the heating device is 60 - 90 minutes.

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