Carbon fiber composite material flat plate joint and preparation method thereof

Abstract

The present invention discloses a carbon fiber composite flat plate joint and a preparation method thereof. The preparation method includes utilizing different directions and angles of carbon fiber prepreg tows to be laid so as to bundle and interlock the flat plate joint preform with the web preform. The present application changes the enveloping method so as to bundle the carbon fiber tows in the flat plate joint, thereby improving the impact impedance and damage tolerance of the carbon fiber composite flat plate joint. At the same time, the preparation method of the present application does not introduce heterogeneous materials, and the carbon fiber composite flat plate joint is integrally formed without additional preparation processes. It only utilizes carbon fiber tows at different angles for enveloping to achieve bonding and interlocking between the tows, significantly improving the impact resistance and post-impact participation performance of the carbon fiber composite flat plate joint, thereby achieving the purpose of optimizing structural performance.

Description

Technical Field

[0001] The invention belongs to the field of composite material joints, and particularly relates to a carbon fiber composite material flat plate joint and a preparation method thereof. Background Art

[0002] Carbon fiber composites are becoming a high-quality alternative to traditional metal materials due to their superior physical and mechanical properties, such as high specific strength, high specific stiffness, excellent fatigue resistance, and superior structural designability. Composite plate joints, as a typical thin-walled aircraft structure, inherit the advantages of thin-walled structures: light weight, large internal effective volume, high torsional stability, and high buckling strength. Furthermore, composite plate joints can be formed using an integral molding process, significantly reducing the number of fasteners and achieving high structural efficiency. However, in plate joints, the stiffener and web are joined using co-curing or high-strength adhesives, which determines the structural strength of the joint. This also results in weak impact resistance. When subjected to impact loads, such as those during aircraft manufacturing, assembly, transportation, and service, these impacts can affect the aircraft's continued serviceability. These impacts, such as from dropped tools, runway sand and gravel splashes, and even bird strikes during flight, can easily lead to delamination, matrix cracking, and fiber breakage. These damage severely impact mechanical properties, resulting in a reduction in residual performance after impact, such as a 40%-60% decrease in compressive strength.

[0003] Research into carbon fiber composite materials' progress in resisting interlaminar delamination and improving the connection performance of flat plate joints is crucial for ensuring the material's load-bearing capacity and optimizing the service performance of structures. Currently, research in this field has achieved certain results both domestically and internationally. Research focusing on technologies and applications that enhance the through-thickness performance of carbon fiber composite laminates has become a mainstream development trend, demonstrating significant improvements.

[0004] Reference [1] Jiahe Ma, Qiang Xu, Weidong Zhu, Yinglin Ke, Translaminarenveloping ply for CFRP interlaminar toughening, Composites Part B: Engineering, 250(2023)110464, discloses a carbon fiber composite interlaminar toughening and a manufacturing method thereof, specifically relating to the technical field of interlaminar toughening of composite materials. The manufacturing method comprises manually laying carbon fiber prepregs and bundling and locking the prepregs with an envelope layer, and then curing and molding them in an autoclave. The carbon fiber prepreg tows in the envelope layer are used to envelop and lock the remaining prepreg tows, thereby improving the anti-delamination ability of the laminate.

[0005] Chinese patent publication number CN116330712A discloses a carbon fiber composite T-joint and its preparation method, specifically in the field of composite joint technology. The manufacturing method is to use a layer of carbon fiber prepreg in different directions at the T-joint to connect the T-joint to the web, and then use an autoclave to cure and shape it.

[0006] The aforementioned literature and patents meet the practical requirements for interlaminar toughening and improve the interlaminar fracture toughness of carbon fiber laminates and T-joints. However, the impact of these joint preparation methods on the impact resistance and damage tolerance of flat joints is unclear.

[0007] Therefore, there is an urgent need to design a method for preparing carbon fiber composite flat plate joints with high impact resistance and damage tolerance. Summary of the Invention

[0008] The invention provides a method for preparing a carbon fiber composite material flat plate joint. The carbon fiber composite material flat plate joint prepared by the preparation method has high interlaminar fracture toughness.

[0009] A specific embodiment of the present invention provides a method for preparing a carbon fiber composite material flat plate joint, comprising:

[0010] S1. Laying first carbon fiber prepreg tows at intervals according to a first laying angle on the surface of the skin web preform to obtain a first carbon fiber prepreg tow array;

[0011] S2. Defining a stiffener region from a region corresponding to the skin web preform, and laying a second carbon fiber prepreg tow on the first carbon fiber prepreg tow array in the stiffener region at a first laying angle to form a second carbon fiber prepreg tow array;

[0012] S3, continuously laying a third carbon fiber prepreg tow on the first and second carbon fiber prepreg tow arrays and in the grooves between the first carbon fiber prepreg tow arrays at a second laying angle to form a third carbon fiber prepreg tow array;

[0013] S4, laying fourth carbon fiber prepreg tows in the grooves spaced apart by the first carbon fiber prepreg tow arrays at a first laying angle to obtain a fourth carbon fiber prepreg tow array;

[0014] S5. Lay the fifth carbon fiber prepreg tow on the fourth carbon fiber prepreg tow array in the stiffener area according to the first laying angle to obtain a stiffener interlocking structure, and attach the stiffener plate preform to the stiffener interlocking structure to obtain a carbon fiber composite material flat plate joint.

[0015] Preferably, the difference between the first laying angle and the second laying angle is 45° or -135°.

[0016] Preferably, the sum of the heights of the first and second carbon fiber prepreg tows is the same as the sum of the heights of the fourth and fifth carbon fiber prepreg tows.

[0017] Preferably, the height of the third carbon fiber prepreg tow is 45° or -135° of the height of the first carbon fiber prepreg tow.

[0018] Preferably, the reinforcement rib area is located in the middle of the area corresponding to the skin web preform.

[0019] Preferably, the first carbon fiber prepreg tows are laid on the surface of the skin web preform at odd horizontal intervals based on a first laying angle;

[0020] The fourth carbon fiber prepreg tows are laid in even rows based on the first laying angle in the grooves spaced apart by the first carbon fiber prepreg tow array in the corresponding area of ​​the skin web preform.

[0021] Preferably, the method for preparing the skin and web preform comprises: continuously laying carbon fiber prepreg tows or directly laying a layer of carbon fiber prepreg on the surface of the skin and web mold to obtain the skin and web preform.

[0022] Preferably, the area corresponding to the first carbon fiber prepreg tow array is the same size as the area corresponding to the skin web preform;

[0023] The area corresponding to the fourth carbon fiber prepreg tow array has the same size as the area corresponding to the skin and web preform.

[0024] A specific embodiment of the present invention further provides a carbon fiber composite material flat plate joint, which is prepared by the above-mentioned method for preparing a carbon fiber composite material flat plate joint.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This application utilizes the laying method and angle of carbon fiber prepreg tows in different directions to bundle and interlock the stiffener plate preform and the skin web preform. This application changes the enveloping method to bundle the carbon fiber tows in the flat joint, thereby improving the impact impedance and damage tolerance of the carbon fiber composite flat joint. At the same time, compared with the existing Z-pinning, film and other carbon fiber composite flat joint preparation technologies, this application does not introduce heterogeneous materials. At the same time, the carbon fiber composite flat joint is formed in one piece without additional preparation process. It only uses carbon fiber tows at different angles for enveloping to achieve the bonding and interlocking effect between the tows, significantly improving the impact resistance and post-impact participation performance of the carbon fiber composite flat joint, and achieving the purpose of optimizing structural performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flow chart of a method for preparing a carbon fiber composite flat plate joint provided in an embodiment of the present application;

[0028] Figure 2 A schematic diagram of a method for preparing a carbon fiber composite flat plate joint provided in an embodiment of the present application;

[0029] Figure 3 A schematic diagram of the interlayer envelope structure of a carbon fiber composite T-joint provided in an embodiment of the present application;

[0030] Figure 4 A CT scan of the internal damage of an interlayer envelope structure specimen of a carbon fiber composite flat plate joint provided in a preferred embodiment of the present application obtained under an impact energy of 30J;

[0031] Figure 5 A schematic diagram of the internal delamination area of ​​an interlayer envelope structure specimen of a carbon fiber composite flat plate joint provided in a preferred embodiment of the present application obtained under an impact energy of 30J;

[0032] Figure 6 The impact response diagram of the interlayer envelope structure specimen of the carbon fiber composite material flat plate joint provided in the preferred embodiment of the present application under 30J impact energy and the result diagram of the compressive strength after impact;

[0033] Figure 7 The impact response diagram of the interlayer envelope structure specimen of the carbon fiber composite material flat plate joint provided in the preferred embodiment of the present application under 15J impact energy and its post-impact bending strength result diagram.

[0034] Among them, there are a first carbon fiber prepreg tow 100, a second carbon fiber prepreg tow 200, a third prepreg tow 300, a fourth prepreg tow 400, a fifth prepreg tow 500, a flat plate interlocking structure 610, a stiffener interlocking structure 620, a skin web mold 700, a skin web preform 800, a stiffened plate mold 900, a stiffened plate preform 1000, and a carbon fiber composite material flat plate interlocking joint 1100. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts or improvements are within the scope of protection of the present invention.

[0036] In order to achieve the goal of preparing a carbon fiber composite material flat plate joint with high interlaminar fracture toughness, the specific embodiment of the present invention is to achieve the goal of preparing a carbon fiber composite material flat plate joint with high interlaminar fracture toughness, such as Figure 1 、 Figure 2 Shown, including:

[0037] S100, such as Figure 2 As shown in a, carbon fiber composite materials are laid on the surface of the skin and web mold 700 to obtain skin and web preforms 800.

[0038] Specifically, a skin web preform is obtained by seamlessly laying a carbon fiber prepreg tow or directly laying a layer of carbon fiber prepreg on the surface of a skin web mold.

[0039] S200, such as Figure 2 As shown in b, first carbon fiber prepreg tows 100 are laid at intervals according to a first laying angle on the surface of the skin web preform to obtain a first carbon fiber prepreg tow array.

[0040] Specifically, starting from the edge surface of the skin and web preform, the first carbon fiber prepreg tows 100 are horizontally laid at odd intervals at a laying angle of -45° and ending at the edge to obtain a first carbon fiber prepreg tow array. During the laying process, grooves are formed in the interval areas of the first carbon fiber prepreg tows 100.

[0041] S300, such as Figure 2 As shown in c, a reinforcement area is set from the area corresponding to the skin web preform 800, and a second carbon fiber prepreg tow 200 is laid on the first carbon fiber prepreg tow array in the reinforcement area according to a first laying angle to form a second carbon fiber prepreg tow array.

[0042] Specifically, after the first carbon fiber prepreg tow array is laid out, a reinforcement area is set in the first carbon fiber prepreg tow array. In a specific embodiment, the reinforcement area is set in the middle position of the area corresponding to the skin web preform. Setting the reinforcement area in the middle position is beneficial for various areas to share the impact force when impacted.

[0043] In a specific embodiment of the present invention, a second carbon fiber prepreg tow 200 is laid on the first carbon fiber prepreg tow array in the reinforcing rib area, so that the groove in the reinforcing rib area is deeper, thereby making the interlocking ability between the carbon fibers in the reinforcing rib area stronger.

[0044] S400, such as Figure 2As shown in d, the third carbon fiber prepreg tow 300 is continuously laid on the first and second carbon fiber prepreg tow arrays and in the grooves spaced apart by the first carbon fiber prepreg tow array according to the second laying angle to form a third carbon fiber prepreg tow array. It can be understood that the grooves spaced apart by the first carbon fiber prepreg tow array and the grooves spaced apart by the second carbon fiber prepreg tow array are the same grooves.

[0045] Specifically, the third carbon fiber prepreg tow 300 provided in the specific embodiment of the present invention is laid at a second laying angle. In one embodiment, the second laying angle is 90°. It is continuously laid in a mixed prepreg tow area constructed by the first carbon fiber prepreg tow array and the second carbon fiber prepreg tow array, and the grooves separated by the first carbon fiber prepreg tow array, thereby completely wrapping the mixed prepreg tow area. The difference in laying angles of the first carbon fiber prepreg tow 100 and the third carbon fiber prepreg tow 300 provided in the specific embodiment of the present invention is 45° or -135°.

[0046] S500, such as Figure 2 As shown in FIG. 5 , the fourth carbon fiber prepreg tow array is obtained by laying the fourth carbon fiber prepreg tow 400 in the grooves spaced apart by the first carbon fiber prepreg tow array according to the first laying angle.

[0047] Specifically, the specific embodiment of the present invention lays the fourth carbon fiber prepreg tow 400 in the grooves spaced apart by the first carbon fiber prepreg tow array in an even-numbered row according to the first laying angle, thereby forming a flat interlocking structure 610 in the area corresponding to the skin web preform 800.

[0048] S600, such as Figure 2 As shown in FIG. 5 , the fifth carbon fiber prepreg tow 500 is laid on the fourth carbon fiber prepreg tow array in the reinforcement area according to the first laying angle to obtain a reinforcement interlocking structure 620 .

[0049] Specifically, the specific embodiment of the present invention lays the fifth carbon fiber prepreg tow 500 on the fourth carbon fiber prepreg tow array in the rib area to enhance the flat interlocking structure 610 to form a rib interlocking structure 620. The interlocking of the cross-layer envelope structure formed by the flat interlocking structure 610 and the rib interlocking structure 620 provided by the specific embodiment of the present invention has a 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. The present invention only arranges the rib interlocking structure 620 in the rib area to reduce the cumbersome preparation process and shorten the preparation cycle. At the same time, the application of the rib interlocking structure 620 to the skin web area does not enhance the delamination suppression effect and cannot improve the impact resistance of the reinforced flat plate.

[0050] In a specific embodiment, the thickness of the first carbon fiber prepreg tow 100, the second carbon fiber prepreg tow 200, the fourth prepreg tow 400, and the fifth prepreg tow 500 are all 0.375 mm, and the thickness of the third prepreg tow 300 is 0.125 mm. The schematic diagram of the interlocking area 620 of the laid reinforcement ribs formed by the above thickness combination is shown in FIG. Figure 3 Its mechanical properties are shown in Figure 5 ,like Figure 6 , Figure 7 As shown in the figure, the 1mm cross-layer envelope structure can improve the residual ultimate compressive strength of the quasi-isotropically laminated carbon fiber composite flat plate joint with a total thickness of 6mm (skin web thickness 4mm + stiffener thickness 2mm) by about 30% under 30J impact energy, and increase the residual bending displacement by nearly 100% and the bending load by about 80% under 15J impact energy.

[0051] S700, such as Figure 2 As shown in FIG. 6 , the rib interlocking structure 620 is attached to the rib preform 1000 that has been laid on the rib mold 900 to obtain a carbon fiber composite material flat plate joint 1100 .

[0052] like Figure 3 As shown, by using the carbon fiber prepreg laying method of the present application, the envelope layer can be evenly, neatly and regularly distributed on the upper and lower sides of the ribs and webs, thereby combining and bundling the layers on the upper and lower sides in the thickness direction, thereby improving the impact impedance and damage tolerance of the flat plate joint.

[0053] like Figure 4 As shown in the figure, CT scans of the secondary bonded, co-cured, and cross-layer enveloped specimens subjected to a 30J impact energy clearly demonstrate the internal damage of the flat plate joint. Both the co-cured and secondary bonded specimens exhibited significant delamination at the stiffener-web interface. Protected by the envelope layer, the cross-layer enveloped specimens maintained structural integrity, with only minor cracks appearing above and below the envelope layer, thanks to the layer's interlocking effect on the laminated layers and the robust properties of its longitudinal fibers to resist the tensile, compressive, and shear stresses generated by the impact.

[0054] like Figure 5 As shown in the figure, under 30J energy impact, the internal damage delamination area diagram of the secondary bonded specimen, co-cured specimen and cross-layer envelope specimen clearly shows the degree of damage of the three types of flat plate joints. The delamination area of ​​the contact surface between the stiffener and the web of the cross-layer envelope specimen is reduced by 68.8% compared with the co-cured specimen and 58.8% compared with the secondary bonded specimen, while the total delamination area is reduced by 61.3% compared with the co-cured specimen and 58.5% compared with the secondary bonded specimen, thereby improving the impact impedance and damage tolerance of the flat plate joint and achieving the purpose of optimizing structural performance.

[0055] The laying and forming process of the carbon fiber composite flat plate joint provided in this application is simple. Through the design of the laying method of carbon fiber prepreg bundles at different angles, it can produce a binding and interlocking effect on the thickness direction ply of the contact surface between the stiffener and the web at the target lamination position, thereby achieving the enhanced effect of improving impact impedance and upgrading damage tolerance at the target lamination position, for the cross-layer envelope lamination specimen with a configuration thickness of 1mm compared with the standard lamination specimen.

[0056] like Figure 6 As shown, Figure 6 (a) Load-time curves of the specimens prepared by the three processes under 30J energy impact. It can be seen that the cross-layer envelope specimen did not reach the damage threshold load (MDTL) and maintained good integrity. Figure 6 (b) The energy-time curves of the test pieces prepared by the three processes under 30J energy impact. It can be seen that the energy absorption rate of the cross-layer envelope sample is much higher than that of the other two. Figure 6 (c) Load-displacement curves of the specimens prepared by the three processes under 30J impact energy. It can be seen that the maximum displacement and residual displacement of the cross-layer envelope specimen are much smaller than those of the other two, indicating that the cross-layer envelope test specimen still has relatively high stiffness after impact. Figure 6 (d) The load-displacement curves of the test specimens prepared by the three processes under compression test after 30J energy impact. It can be seen that the cross-layer envelope specimen has a higher maximum load and maximum displacement, and the residual ultimate compressive strength is increased by about 30% under 30J impact energy.

[0057] like Figure 7 As shown, Figure 7 (a) Load-time curves of the specimens prepared by the three processes under 15J impact energy. It can be seen that the cross-layer envelope specimen has a higher ultimate load and has stronger impact energy resistance. Figure 7 (b) The energy-time curves of the test pieces prepared by the three processes under 15J energy impact, from which it can be seen that the energy absorption rate of the cross-layer envelope sample is higher than that of the other two; Figure 7 (c) The load-displacement curves of the test specimens prepared by the three processes under 15J energy impact. It can be seen that the maximum displacement and residual displacement of the cross-layer envelope specimen are smaller than those of the other two, indicating that the cross-layer envelope test specimen still has relatively high stiffness after impact. Figure 7 (d) The load-displacement curves of the specimens prepared by the three processes under the bending test after 15J impact energy. It can be seen that the cross-layer envelope specimen has a higher maximum load and maximum displacement, and increases the residual bending displacement by nearly 100% and the bending load by about 80% under 15J impact energy.

[0058] The present invention is based on the designability of the layup of carbon fiber flat plate joints and has layup feasibility. It fully utilizes the fiber directional performance advantages of carbon fiber prepreg tows and implements a cross-layer envelope lamination configuration at the target lamination position of the rib and skin junction of the carbon fiber composite material flat plate joint without destroying the fiber and resin matrix, introducing foreign materials, or increasing the weight of the component, thereby improving the impact impedance and damage tolerance of the flat plate joint and achieving the purpose of optimizing structural performance.

[0059] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a carbon fiber composite material flat plate joint, characterized in that: include: S1. Laying first carbon fiber prepreg tows at intervals according to a first laying angle on the surface of the skin web preform to obtain a first carbon fiber prepreg tow array; S2. Defining a stiffener region from a region corresponding to the skin web preform, and laying a second carbon fiber prepreg tow on the first carbon fiber prepreg tow array in the stiffener region at a first laying angle to form a second carbon fiber prepreg tow array; S3, continuously laying a third carbon fiber prepreg tow on the first and second carbon fiber prepreg tow arrays and in the grooves between the first carbon fiber prepreg tow arrays at a second laying angle to form a third carbon fiber prepreg tow array; S4, laying fourth carbon fiber prepreg tows in the grooves spaced apart by the first carbon fiber prepreg tow arrays at a first laying angle to obtain a fourth carbon fiber prepreg tow array; S5. Lay the fifth carbon fiber prepreg tow on the fourth carbon fiber prepreg tow array in the stiffener area according to the first laying angle to obtain a stiffener interlocking structure, and attach the stiffener plate preform to the stiffener interlocking structure to obtain a carbon fiber composite material flat plate joint.

2. The method for preparing a carbon fiber composite material flat plate joint according to claim 1, characterized in that: The difference between the first laying angle and the second laying angle is 45° or -135°.

3. The method for preparing a carbon fiber composite material flat plate joint according to claim 1, characterized in that: The sum of the heights of the first and second carbon fiber prepreg tows is the same as the sum of the heights of the fourth and fifth carbon fiber prepreg tows.

4. The method for preparing a carbon fiber composite material flat plate joint according to claim 1, characterized in that: The height of the third carbon fiber prepreg tow is from one half to one half of the height of the first carbon fiber prepreg tow.

5. The method for preparing a carbon fiber composite material flat plate joint according to claim 1, characterized in that: The reinforcing rib area is located in the middle of the area corresponding to the skin web preform.

6. The method for preparing a carbon fiber composite material flat plate joint according to claim 1, characterized in that: The first carbon fiber prepreg tows are laid on the surface of the skin web preform at odd horizontal intervals based on a first laying angle; The fourth carbon fiber prepreg tows are laid in even rows based on the first laying angle in the grooves spaced apart by the first carbon fiber prepreg tow array in the corresponding area of ​​the skin web preform.

7. The method for preparing a carbon fiber composite material flat plate joint according to claim 1, characterized in that: The method for preparing the skin and web preform comprises: continuously laying carbon fiber prepreg tows or directly laying a layer of carbon fiber prepreg on the surface of the skin and web mold to obtain the skin and web preform.

8. The method for preparing a carbon fiber composite material flat plate joint according to claim 1, characterized in that: The area corresponding to the first carbon fiber prepreg tow array has the same size as the area corresponding to the skin web preform; The area corresponding to the fourth carbon fiber prepreg tow array has the same size as the area corresponding to the skin and web preform.

9. A carbon fiber composite material flat plate joint, characterized in that: The carbon fiber composite material flat plate joint is prepared by the preparation method of any one of claims 1 to 8.

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