A carbon fiber composite T-joint and a method of making the same

Abstract

The application discloses a preparation method of a carbon fiber composite T-shaped joint. The method comprises the following steps: laying carbon fiber composite materials on surfaces of two L-shaped web molds and a skin web mold to obtain two L-shaped web preforms and a skin web preform; laying first carbon fiber pre-impregnated tows side by side and adjacently from surfaces of vertical sections of the L-shaped web preforms, and reserving backing paper on the first carbon fiber pre-impregnated tows when laying reaches surfaces of flat sections; adhering the vertical sections of the L-shaped web preforms, and simultaneously forming a triangular filling area; and flattening the triangular filling area to obtain a T-shaped structure preform; forming an interlocking area on the T-shaped structure preform; and combining the T-shaped structure preform and the skin web preform by using the interlocking area to form the carbon fiber composite T-shaped joint. The method is simple and efficient, and the carbon fiber composite T-shaped joint prepared by the method has high interlayer fracture toughness. The application further provides a carbon fiber composite T-shaped joint.

Description

Technical Field

[0001] This invention belongs to the field of composite material joints, specifically relating to a carbon fiber composite material T-joint and its preparation method. Background Technology

[0002] Carbon fiber composites are inorganic high-performance fibers with a carbon content of over 90%, which are transformed from organic fibers through a series of heat treatments. They are a new material with excellent mechanical properties, possessing the inherent characteristics of carbon materials, while also having the softness and processability of textile fibers. They are a new generation of reinforcing fibers.

[0003] Carbon fiber composites are widely used in aerospace, automotive, shipbuilding, and wind turbine blades due to their superior specific strength, specific stiffness, specific modulus, and fatigue resistance. They are also used as high-performance engineering materials for enhancing structural performance and achieving lightweight design in primary and secondary T-joints that transfer complex loads between orthogonal structural members.

[0004] Carbon fiber composite laminates, achieved using carbon fiber prepreg layup technology, are a typical application. However, in actual working conditions, delamination is the main failure mode of carbon fiber composite laminates under lateral bending, circumferential torsion, and combined loads, caused by interlaminar shear stress. In particular, delamination and debonding at the component joint of carbon fiber composite T-joints severely limit the performance of the structure.

[0005] Research on the anti-delamination properties of carbon fiber composites and the improvement of T-joint connection performance of carbon fiber composites is of great significance for ensuring the load-bearing capacity of materials and optimizing the service life of structures. Currently, relevant research both domestically and internationally has made some progress, with the thickness-direction reinforcement technology and its application in carbon fiber composite laminates showing significant improvement effects becoming the mainstream development direction.

[0006] Chinese patent CN114683587A discloses a carbon fiber composite T-joint and its manufacturing and repair methods, specifically relating to the field of composite material joint technology. The manufacturing method involves manually laying carbon fiber prepreg and mixing it with shape memory alloy wires, shaping it, and then curing it in a temperature chamber. Due to the superelasticity of the shape memory alloy wires, the damaged component has a certain degree of recovery ability. When repair adhesive is added and repaired at high temperature, the shape memory property of the wires allows the component to return to its pre-stretch shape and extrudes excess adhesive. The carbon fiber composite T-joint repaired using this process can recover 80%-90% of its pre-damage tensile strength.

[0007] The aforementioned patents meet the practical repair needs, shorten the repair cycle, and transform the component replacement repair method into a restorative repair method, thus saving repair costs. However, the introduction of heterogeneous materials such as adhesives in these patents increases the weight of the components and has a certain impact on the bonding ability against delamination and debonding.

[0008] Therefore, there is an urgent need to design a method for preparing carbon fiber composite T-joints with high interlaminar fracture toughness. Summary of the Invention

[0009] The purpose of this application is to provide a carbon fiber composite T-joint and its preparation method. Through this application, a carbon fiber composite T-joint with high interlaminar fracture toughness can be prepared.

[0010] To achieve the above objectives, the technical methods adopted in the embodiments of this application are as follows:

[0011] On one hand, embodiments of this application provide a method for preparing a carbon fiber composite T-joint, comprising:

[0012] (1) Two L-shaped web preforms are obtained by laying carbon fiber composite material on the surface of two L-shaped web molds respectively, and a skin web preform is obtained by laying carbon fiber composite material on the surface of skin web mold.

[0013] (2) The L-shaped web preform includes a straight section, a chamfered section and a vertical section in sequence. Starting from the surface of the vertical section of the L-shaped web preform, the first carbon fiber prepreg bundles are laid side by side and adjacent to each other. When laid to the surface of the straight section, the backing paper on the first carbon fiber prepreg bundles is retained at intervals. The backing paper faces the straight section of the L-shaped web preform.

[0014] (3) The vertical segments of the two L-shaped web preforms obtained in step (2) are attached together. At the same time, the chamfered segments of the two L-shaped web preforms obtained in step (2) form a triangular filling area. The triangular filling area is filled with carbon fiber composite material to obtain a T-shaped structure preform. The straight segments of the two L-shaped web preforms obtained in step (2) and the filled triangular area are used to construct the straight area of ​​the T-shaped structure preform.

[0015] (4) Lay a second carbon fiber prepreg bundle on the surface of the flat area to form a first carbon fiber prepreg bundle laying area. The first carbon fiber prepreg bundle laying area includes a peeling area and a laying sub-area. The peeling area is composed of the flat section surface of the L-shaped web preform exposed after peeling off the first carbon fiber prepreg bundle with the backing paper.

[0016] (5) Lay a third carbon fiber prepreg bundle on the surface of the uncovered area and the laying sub-area to form a second carbon fiber prepreg bundle laying area. Remove the backing paper retained by the first carbon fiber prepreg bundle and weave it with the third carbon fiber prepreg bundle to form a laying interlocking area. The laying angle of the third carbon fiber prepreg bundle is different from that of the first carbon fiber prepreg bundle.

[0017] (6) The skin web preform is bonded to the first carbon fiber prepreg bundle laying area and the layup interlocking area to obtain a carbon fiber composite material T-joint.

[0018] Furthermore, a third carbon fiber prepreg bundle is laid on the surface of the uncovered area and the laying sub-area. The laying method is to lay them side by side and adjacent to each other. The laying angle of the third carbon fiber prepreg bundle is 45°-135° different from the laying angle of the first carbon fiber prepreg bundle.

[0019] Furthermore, the dimensions of the second carbon fiber prepreg tow laying area are the same as the dimensions of the straight area of ​​the T-shaped preform.

[0020] Furthermore, a second carbon fiber prepreg bundle is laid on the surface of the flat area to form a first carbon fiber prepreg bundle laying area. The laying method is to lay them side by side and adjacent to each other. The laying angle of the second carbon fiber prepreg bundle is the same as the laying angle of the first carbon fiber prepreg bundle on the surface of the flat area.

[0021] Furthermore, the dimensions of the first carbon fiber prepreg tow laying area are the same as the surface dimensions of the skin web preform.

[0022] Furthermore, the specific steps for laying carbon fiber composite material on the surface of the L-shaped web mold or the skin web mold are as follows:

[0023] L-shaped web preforms or skin web preforms are obtained by laying carbon fiber prepreg bundles side by side and adjacent to each other or by directly laying multiple layers of carbon fiber prepreg on the surface of L-shaped web molds or skin web molds.

[0024] Furthermore, before aligning and bonding the vertical segments of the two L-shaped web preforms obtained in step (2), remove the backing paper from the surfaces of the vertical segments and chamfered segments of the two L-shaped web preforms obtained in step (2).

[0025] Furthermore, the specific steps for using carbon fiber composite materials to fill the triangular filling area are as follows:

[0026] The triangular filling area is filled by prepreg of carbon fiber, so that the triangular filling area and the straight sections of the two L-shaped web prefabricated bodies form a plane, thereby obtaining a T-shaped structure prefabricated body.

[0027] Furthermore, after the first carbon fiber prepreg tow retains the backing paper and is interwoven with the third carbon fiber prepreg tow to form an interlocking area, the backing paper is removed.

[0028] On the other hand, this application provides a carbon fiber composite T-joint, which is prepared using the aforementioned method for preparing carbon fiber composite T-joints.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This application utilizes a carbon fiber prepreg tow layup method to create an interlocking bonding area in the bonding region between the T-shaped preform and the skin web preform. Compared with existing technologies such as Z-pinning, through-layer stitching, or interlayer adhesive films in carbon fiber composite engineering applications, this application does not damage the fiber and resin matrix, does not introduce heterogeneous materials, and does not increase the weight of the final carbon fiber composite T-joint. The preparation method is simple, efficient, and has no additional manufacturing costs, thus achieving a reasonable cost. Furthermore, the interlocking structure in the prepared carbon fiber composite T-joint exhibits high interlayer fracture toughness, thereby enhancing the delamination loss suppression effect, improving the anti-delamination and debonding connection ability, and achieving the goal of optimizing structural performance. Attached Figure Description

[0031] Figure 1 A flowchart illustrating the preparation method of the carbon fiber composite T-joint provided in the embodiments of this application;

[0032] Figure 2 This is a schematic diagram of the preparation method of the carbon fiber composite T-joint provided in the embodiments of this application;

[0033] Figure 3 This is a schematic diagram of the interlayer interlocking structure of the carbon fiber composite T-joint provided in the embodiments of this application;

[0034] Figure 4 The maximum failure load and mechanical property response results of the interlayer interlocking structure of the carbon fiber composite T-joint provided in the preferred embodiment of this application are shown in the figure.

[0035] Figure 5 The figure shows the interlaminar delamination behavior and interlaminar fracture toughness mechanical property response results of the interlaminar interlocking structure of the carbon fiber composite T-joint provided in the preferred embodiment of this application.

[0036] The components include: L-shaped web mold 100, L-shaped web preform 200, straight section of L-shaped web preform 210, chamfered section of L-shaped web preform 220, vertical section of L-shaped web preform 230, first carbon fiber prepreg tow 300, backing paper of first carbon fiber prepreg tow 310, triangular filling area 400, second carbon fiber prepreg tow 500, first carbon fiber prepreg tow laying area 600, peeling area 610, laying sub-area 620, third carbon fiber prepreg tow 700, second carbon fiber prepreg tow laying area 800, interlocking layup area 900, skin web mold 1000, and skin web preform 1100. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only a part and not all of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort or improvement are within the scope of protection of the present invention.

[0038] To achieve the goal of preparing carbon fiber composite T-joints with high interlaminar fracture toughness, this application employs a layup method to deposit a ply-interlocking structure with high interlaminar fracture toughness between the skin web and the stiffeners of the T-joint. This enhances the delamination loss suppression effect and improves the anti-delamination and debonding bonding ability of the prepared carbon fiber composite T-joint, thereby optimizing the structural performance. This application provides a method for preparing a carbon fiber composite T-joint, such as... Figure 1 , Figure 2 As shown, it includes:

[0039] S100, such as Figure 2 As shown in a and b, carbon fiber composite material is laid on the surface of two L-shaped web molds 100 to obtain L-shaped web preforms 200, and carbon fiber composite material is laid on the surface of skin web mold 1000 to obtain skin web preforms 1100.

[0040] In one specific embodiment, the specific steps for preparing the L-shaped web preform 200 of this application are as follows: L-shaped web preforms are obtained by laying carbon fiber prepreg bundles side-by-side and adjacent to each other, or by directly laying a layer of carbon fiber prepreg on the surface of the L-shaped web mold. The preparation steps for preparing the skin web preform 900 on the surface of the skin web mold 800 are the same as those for preparing the L-shaped web preform 200.

[0041] S200, a first carbon fiber prepreg tow 300 is laid on the surface of the L-shaped web preform 200, such as... Figure 2 As shown in b and c, the specific steps are as follows:

[0042] The L-shaped web preform 200 includes a straight section 210, a chamfered section 220, and a vertical section 230. Starting from the surface of the vertical section 230 of the L-shaped web preform, the first carbon fiber prepreg bundles 300 are laid side by side at a 45° laying angle. When laying from the chamfered section 220 to the straight section 210, the backing paper 310 of the first carbon fiber prepreg bundles is retained at intervals. The first carbon fiber prepreg bundles 300 without retaining the backing paper are laid to the surface of the straight section 210, and the retained backing paper 310 faces the surface of the straight section 210 of the L-shaped web preform.

[0043] S300, the vertical segments 230 of the two L-shaped web prefabricated bodies obtained in step S200 are joined together to obtain a T-shaped prefabricated body, such as... Figure 2 As shown in d and e, the specific steps are as follows:

[0044] The vertical segments 230 of the two L-shaped web preforms obtained in step S200 are bonded together, that is, the vertical segments 230 on which the first carbon fiber prepreg bundle 300 is laid are bonded together. Before bonding, the backing paper of the vertical segments 230 and the chamfered segments 220 of the two L-shaped web preforms obtained in step S200 is removed. At the same time, the chamfered segments 220 of the two L-shaped web preforms obtained in step S200 form a triangular filling area 400. The triangular filling area 400 is filled with carbon fiber composite material to obtain a T-shaped structure preform. The straight segments 210 of the two L-shaped web preforms obtained in step S200 and the filled triangular area 400 are used to construct the straight area of ​​the T-shaped structure preform.

[0045] In one specific embodiment, the specific steps for using carbon fiber composite material to fill the triangular filling area are as follows: the triangular filling area is filled by carbon fiber prepreg bundles, so that the triangular filling area and the straight sections 210 of the two L-shaped web preforms form a plane, thereby obtaining a T-shaped structure preform.

[0046] S400, such as Figure 2 As shown in f, second carbon fiber prepreg bundles 500 are laid side-by-side and adjacent to each other on the flat surface of the T-shaped precast structure to form a first carbon fiber prepreg bundle laying area 600. The adjacent laying allows for partial overlap between adjacent second carbon fiber prepreg bundles. The first carbon fiber prepreg bundle laying area 600 covers the flat area 210 and extends along the x-direction. The dimensions of the first carbon fiber prepreg bundle laying area 600 are the same as the dimensions of the surface of the skin web precast body 1100. The first carbon fiber prepreg bundle 300 and the second carbon fiber prepreg bundle 500 are laid at the same angle, and the second carbon fiber prepreg bundle 500 and the first carbon fiber prepreg bundle 300 overlap along the laying path.

[0047] The first carbon fiber prepreg tow laying area 600 provided in this embodiment of the invention is divided into a peeling area 610 and a laying sub-area 620, such as... Figure 2 As shown in g, the first carbon fiber prepreg bundle 500 with the backing paper is peeled off from the surface of the L-shaped web preform 200, thereby exposing a portion of the L-shaped web preform 200. The exposed portion of the L-shaped web preform 200 constitutes the peeling area 610. The laying sub-area 620 is composed of the second carbon fiber prepreg bundle 500 laid on the leveling triangular area, and the second carbon fiber prepreg bundle 500 laid on the surface of the first carbon fiber prepreg bundle 300 provided in step S200, which is laid on the surface of the straight section 210.

[0048] S500, such as Figure 2 As shown in g and h, the interlocked region is constructed, and the specific steps are as follows:

[0049] In this embodiment of the application, a third carbon fiber prepreg bundle 700 is laid on the surface of the exposed L-shaped web preform 200 and the surface of the laying area 620 to form a second carbon fiber prepreg bundle laying area 800. The size of the second carbon fiber prepreg bundle laying area 800 is the same as the size of the straight area of ​​the T-shaped structure preform. The laying angle difference between the third carbon fiber prepreg bundle 700 and the second carbon fiber prepreg bundle 500 is 45°.

[0050] like Figure 3 As shown, during the laying of the third carbon fiber prepreg bundle, the first carbon fiber prepreg bundle 300 and the third carbon fiber prepreg bundle 700, with the backing paper 310 retained, are interwoven and laid on the surface of the straight section 210. Then, the backing paper 310 retained by the first carbon fiber prepreg bundle is removed, forming the interlocking area 900. The interlocking of the interlayer envelope structure formed by the third carbon fiber prepreg bundle 700, the first carbon fiber prepreg bundle 300, and the second carbon fiber prepreg bundle 500 has high interlayer fracture toughness, thereby enhancing the delamination loss suppression effect, improving the anti-delamination and debonding connection ability, and achieving the purpose of optimizing structural performance.

[0051] In a preferred embodiment, in the interlocking area 900, the thickness of the first carbon fiber prepreg tow 300 is 1 mm, the thickness of the second carbon fiber prepreg tow 500 is 1 mm, and the thickness of the third carbon fiber prepreg tow 700 is 0.125 mm. The mechanical properties of the interlocking area 900 formed by the above thickness combination are as follows: Figure 3 ,like Figure 4 , Figure 5 As shown, the 2mm cross-layer envelope structure can achieve a maximum delamination failure load increase of over 400% and a type I interlaminar fracture toughness increase of approximately 1800% for standard unidirectional laminated specimens.

[0052] In a preferred embodiment, in the interlocking area 900, the thickness of the first carbon fiber prepreg tow 300 is 0.5 mm, the thickness of the second carbon fiber prepreg tow 500 is 0.5 mm, and the thickness of the third carbon fiber prepreg tow 700 is 0.125 mm. The mechanical properties of the interlocking area 900 formed by the above thickness combination are as follows: Figure 3 ,like Figure 4 , Figure 5 As shown, a 1mm cross-layer envelope structure can achieve nearly 400% of the maximum delamination failure load and approximately 1200% of the type I interlaminar fracture toughness for standard unidirectional laminated specimens.

[0053] S600, such as Figure 2 As shown in i, the skin web preform 1100 obtained in step S100 is bonded to the first carbon fiber prepreg bundle laying area 600 and the laying interlocking area 900 to obtain a carbon fiber composite material T-joint.

[0054] The carbon fiber composite T-joint provided in this application has a simple layup process. Through the design of the layup logic and method of the prepreg carbon fiber bundles, a layup interlocking binding effect along the thickness direction can be formed at the target lamination position, thereby achieving the enhancement effect of improving interlaminar fracture toughness and inhibiting delamination damage at the target lamination position. For cross-layer envelope laminated specimens with 2mm and 1mm configuration thicknesses, compared with standard unidirectional laminated specimens, there is an improvement of approximately 1800% and 1200% in Type I interlaminar fracture toughness, respectively, and an enhancement of approximately 400% in maximum resistance to delamination failure load. This invention relies on the designability of layup, possesses layup feasibility, and fully utilizes the advantages of carbon fiber tensile properties. Without damaging the fiber and resin matrix, introducing heterogeneous materials, or increasing the weight of the component, a cross-layer envelope laminated configuration is implemented at the target lamination position of the rib and skin joint of the carbon fiber composite T-joint, thereby improving the connection ability against delamination and debonding, and achieving the purpose of optimizing structural performance.

[0055] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a carbon fiber composite T-joint, characterized in that, include: (1) Two L-shaped web preforms are obtained by laying carbon fiber composite material on the surface of two L-shaped web molds respectively, and a skin web preform is obtained by laying carbon fiber composite material on the surface of skin web mold. (2) The L-shaped web preform includes a straight section, a chamfered section and a vertical section in sequence. Starting from the surface of the vertical section of the L-shaped web preform, the first carbon fiber prepreg bundles are laid side by side and adjacent to each other. When laid to the surface of the straight section, the backing paper on the first carbon fiber prepreg bundles is retained at intervals. The backing paper faces the straight section of the L-shaped web preform. (3) The vertical segments of the two L-shaped web preforms obtained in step (2) are attached together. At the same time, the chamfered segments of the two L-shaped web preforms obtained in step (2) form a triangular filling area. The triangular filling area is filled with carbon fiber composite material to obtain a T-shaped structure preform. The straight segments of the two L-shaped web preforms obtained in step (2) and the filled triangular area are used to construct the straight area of ​​the T-shaped structure preform. (4) Lay a second carbon fiber prepreg bundle on the surface of the flat area to form a first carbon fiber prepreg bundle laying area. The first carbon fiber prepreg bundle laying area consists of a peeling area and a laying sub-area. The peeling area consists of the surface of the flat section of the L-shaped web preform exposed after peeling off the first carbon fiber prepreg bundle with the backing paper. (5) A third carbon fiber prepreg bundle is laid on the surface of the uncovered area and the laying sub-area to form a second carbon fiber prepreg bundle laying area. During the laying of the third carbon fiber prepreg bundle, the first carbon fiber prepreg bundle with the backing paper retained is woven together with the third carbon fiber prepreg bundle to form a layer interlocking area. The laying angle of the third carbon fiber prepreg bundle is different from that of the first carbon fiber prepreg bundle. (6) The skin web preform is bonded to the first carbon fiber prepreg bundle laying area and the layup interlocking area to obtain a carbon fiber composite material T-joint.

2. The method for preparing a carbon fiber composite T-joint according to claim 1, characterized in that, The third carbon fiber prepreg bundle is laid on the surface of the uncovered area and the laying sub-area. The laying method is to lay them side by side and adjacent to each other. The laying angle of the third carbon fiber prepreg bundle is 45°-135° different from the laying angle of the first carbon fiber prepreg bundle.

3. The method for preparing a carbon fiber composite T-joint according to claim 1, characterized in that, The dimensions of the second carbon fiber prepreg bundle laying area are the same as the dimensions of the straight area of ​​the T-shaped preform.

4. The method for preparing a carbon fiber composite T-joint according to claim 1, characterized in that, A second carbon fiber prepreg bundle is laid on the surface of the flat area to form a first carbon fiber prepreg bundle laying area. The laying method is to lay them side by side and adjacent to each other. The laying angle of the second carbon fiber prepreg bundle is the same as the laying angle of the first carbon fiber prepreg bundle on the surface of the flat area. The laying path of the second carbon fiber prepreg bundle overlaps with the laying path of the first carbon fiber prepreg bundle on the surface of the flat area.

5. The method for preparing a carbon fiber composite T-joint according to claim 1, characterized in that, The dimensions of the first carbon fiber prepreg bundle laying area are the same as the surface dimensions of the skin web preform.

6. The method for preparing a carbon fiber composite T-joint according to claim 1, characterized in that, The specific steps for laying carbon fiber composite material on the surface of L-shaped web mold or skin web mold are as follows: L-shaped web preforms or skin web preforms are obtained by laying carbon fiber prepreg bundles side by side and adjacent to each other or by directly laying multiple layers of carbon fiber prepreg on the surface of L-shaped web molds or skin web molds.

7. The method for preparing a carbon fiber composite T-joint according to claim 1, characterized in that, Before aligning and bonding the vertical sections of the two L-shaped web preforms obtained in step (2), remove the backing paper from the surfaces of the vertical sections and chamfered sections of the two L-shaped web preforms obtained in step (2).

8. The method for preparing a carbon fiber composite T-joint according to claim 1, characterized in that, The specific steps for using carbon fiber composite materials to fill the triangular infill areas are as follows: The triangular filling area is filled by prepreg of carbon fiber, so that the triangular filling area and the straight sections of the two L-shaped web prefabricated bodies form a plane, thereby obtaining a T-shaped structure prefabricated body.

9. The method for preparing a carbon fiber composite T-joint according to claim 1, characterized in that, After the first carbon fiber prepreg bundle with the retained backing paper is woven together with the third carbon fiber prepreg bundle to form an interlocking area, the backing paper of the first carbon fiber prepreg bundle is removed.

10. A carbon fiber composite T-joint, characterized in that, The carbon fiber composite T-joint was prepared using the preparation method described in any one of claims 1-9.

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