Carbon fiber composite material flat plate joint and preparation method thereof

Abstract

The invention discloses a carbon fiber composite flat plate joint and a preparation method thereof, and the preparation method comprises the step of binding and interlocking a flat plate joint prefabricated body and a web prefabricated body by utilizing laying modes and angles of carbon fiber prepreg tows in different directions. And the carbon fiber tows are bound in the flat plate joint, so that the impact resistance and the damage tolerance of the carbon fiber composite flat plate joint are improved. Meanwhile, according to the preparation method, heterogeneous materials are not introduced, meanwhile, the carbon fiber composite material flat plate connector is integrally formed, an additional preparation technology is not carried out, and only carbon fiber tows with different angles are utilized for enveloping, so that the combination and interlocking effects between the tows are achieved; the impact resistance and the participation performance after impact of the carbon fiber composite flat plate joint are remarkably improved, and the purpose of optimizing the structural performance is achieved.

Description

Technical Field

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

[0002] Carbon fiber composite materials have gradually become a high-quality substitute for traditional metal materials due to their excellent physical and mechanical properties, such as high specific strength, high specific stiffness, good fatigue resistance, and excellent structural designability. As a typical thin-walled structure of aircraft, composite flat plate joints inherit the advantages of thin-walled structures, such as light weight, large internal effective space, high torsional stability and buckling strength; in addition, composite flat plate joints can also adopt an integral molding process, which greatly reduces the number of fasteners and has a high structural efficiency. However, in the flat plate joint, the stiffening plate and the web are connected by co-curing or high-strength adhesives, which determines the structural strength of the flat plate joint. This also makes the flat plate joint weak in impact resistance. After being subjected to impact loads, such as during the manufacturing, assembly, transportation, and service of the aircraft, it is extremely susceptible to impact loads, thereby affecting the continued service of the aircraft, such as tool drops, sand and gravel splashing on the runway, and even bird strikes during flight. Flat plate joints are prone to damage such as delamination, matrix cracking, and fiber breakage, which seriously affects the mechanical properties and causes the residual performance to decrease after the impact, such as a 40%-60% decrease in compressive performance.

[0003] Research on the progress of carbon fiber composite materials in resisting interlayer delamination and improving the connection performance of flat joints is crucial to ensure the load-bearing capacity of materials and optimize the service performance of structures. At present, research in this field at home and abroad has achieved certain results, and research with the technology and application of enhancing the thickness direction performance of carbon fiber composite laminates as the prominent feature has become the mainstream development trend in this field, showing significant improvement effects.

[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 material 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 prepreg and bundling and locking the prepreg with an enveloping layer, and then curing and molding with an autoclave. The carbon fiber prepreg tows of the enveloping layer are used to envelop and lock the remaining prepreg tows, thereby improving the anti-delamination ability of the laminate.

[0005] A Chinese patent with publication number CN116330712A discloses a carbon fiber composite T-joint and a preparation method thereof, 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 with the web, and then use a hot autoclave to cure and shape it.

[0006] The above documents and patents meet the actual interlayer toughening requirements and improve the interlayer fracture toughness of carbon fiber laminates and T-joints. However, the effect of the above joint preparation method on the impact impedance and damage tolerance of the flat joint is unclear.

[0007] Therefore, there is an urgent need to design a method for preparing carbon fiber composite flat plate joints with higher 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 higher 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, setting a stiffener area from an area 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 area according to a first laying angle to form a second carbon fiber prepreg tow array;

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

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

[0014] S5. Lay a fifth carbon fiber prepreg tow on the fourth carbon fiber prepreg tow array in the stiffener area at a first laying angle to obtain a stiffener interlocking structure, and fit a stiffener plate preform on 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 carbon fiber prepreg tow and the second carbon fiber prepreg tow is the same as the sum of the heights of the fourth carbon fiber prepreg tow and the fifth carbon fiber prepreg tow.

[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 reinforcing 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-numbered horizontal intervals based on a first laying angle;

[0020] The fourth carbon fiber prepreg tows are laid in even-numbered rows based on the first laying angle in the grooves spaced apart by the first carbon fiber prepreg tow arrays 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 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 preparation method of the 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 methods and angles 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, adhesive 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 integrally formed without additional preparation processes. 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 material 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 material 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 material 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 material 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 obtained by 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;

[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 post-impact compressive strength;

[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 be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work or improvement 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 higher 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 higher interlaminar fracture toughness, such as Figure 1 , Figure 2 As 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, the 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 the 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, the first carbon fiber prepreg tows 100 are horizontally laid at odd-numbered rows with a laying angle of -45° starting from the edge surface of the skin and web preform and ending at the edge to obtain a first carbon fiber prepreg tow array. During the laying process, grooves are formed in the spacing areas of the first carbon fiber prepreg tows 100.

[0041] S300, such as Figure 2 As shown in c, a reinforcement rib 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 rib 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 rib area is set in the first carbon fiber prepreg tow array. In a specific embodiment, the reinforcement rib area is set in the middle position of the area corresponding to the skin web preform. Setting the reinforcement rib area in the middle position is beneficial to sharing the impact force among various areas 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, so as to completely wrap 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 e, 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 at a 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 at a 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 rib area according to the first laying angle to obtain the reinforcement rib 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 region to strengthen the flat plate interlocking structure 610 to form a rib interlocking structure 620. The interlocking of the cross-layer envelope structure formed by the flat plate interlocking structure 610 and the rib interlocking structure 620 provided in the specific embodiment of the present invention has a high interlaminar 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 region 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 region 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 reinforcing ribs formed by the above-mentioned thickness combination is shown in FIG. Figure 3 Its mechanical properties are shown in Figure 5 ,like Figure 6 , Figure 7 As shown, 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 g, the rib interlocking structure 620 is attached to the rib plate preform 1000 that has been laid on the rib plate 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 rib plate and the web, 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 joint.

[0053] like Figure 4 As shown in the figure, under 30J energy impact, the CT scans of the secondary bonded specimens, co-cured specimens and cross-layer envelope specimens clearly show the internal damage of the flat plate joints. It can be found that the co-cured specimens and the secondary bonded specimens have obvious stratification at the contact surface between the stiffener and the web. Under the protection of the envelope layer, the cross-layer envelope specimen combines and interlocks the layers, and uses the strong performance of the longitudinal fibers to resist the tensile, compressive and shear stresses generated by the impact, still maintaining the integrity of the structure, with only slight cracks appearing on the upper and lower sides of the envelope layer.

[0054] like Figure 5 As shown in the figure, under 30J energy impact, the internal damage delamination area diagram of the secondary bonding specimen, co-curing 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-curing specimen and 58.8% compared with the secondary bonding specimen, while the total delamination area is reduced by 61.3% compared with the co-curing specimen and 58.5% compared with the secondary bonding specimen, which improves the impact impedance and damage tolerance of the flat plate joint and achieves the purpose of optimizing the structural performance.

[0055] The laying and forming process of the carbon fiber composite flat plate joint provided in the present application is simple. Through the laying method design of carbon fiber prepreg bundles at different angles, it can produce a binding and interlocking effect on the thickness direction of the ply at the contact surface of the rib plate and the web at the target lamination position, thereby achieving the enhanced effect of improving the impact impedance and upgrading the 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) is the load-time curve of the test pieces prepared by 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) is the energy-time curve of the test pieces prepared by the three processes under 30J energy impact, from which 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) is the load-displacement curve of the test pieces prepared by the three processes under 30J energy impact. It can be seen that the maximum displacement and residual displacement of the cross-layer envelope specimen are much smaller than the other two, indicating that the cross-layer envelope test still has a relatively high stiffness after impact; Figure 6 (d) is the load-displacement curve of the test pieces prepared by the three processes under the 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) is the load-time curve of the test pieces prepared by three processes under 15J energy impact. It can be seen that the cross-layer envelope specimen has a higher ultimate load and has stronger impact resistance; Figure 7 (b) is the energy-time curve 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) is the load-displacement curve of the test pieces 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 the other two, indicating that the cross-layer envelope test still has a relatively high stiffness after impact; Figure 7 (d) is the load-displacement curve of the bending test of the test pieces prepared by the three processes 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 has the feasibility of laying out based on the designability of carbon fiber flat plate joints, gives full play to the fiber directional performance advantages of carbon fiber prepreg tows, and implements a cross-layer enveloping 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, and 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 the structural performance.

[0059] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. 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, setting a stiffener area from an area 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 area according to a first laying angle to form a second carbon fiber prepreg tow array; S3, continuously laying a third carbon fiber prepreg tow array on the first and second carbon fiber prepreg tow arrays and in the grooves spaced apart by the first carbon fiber prepreg tow array at a second laying angle to form a third carbon fiber prepreg tow array; S4, laying a fourth carbon fiber prepreg tow in the grooves spaced apart by the first carbon fiber prepreg tow array at a first laying angle to obtain a fourth carbon fiber prepreg tow array; S5. Lay a fifth carbon fiber prepreg tow on the fourth carbon fiber prepreg tow array in the stiffener area at a first laying angle to obtain a stiffener interlocking structure, and fit a stiffener plate preform on 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 carbon fiber prepreg tow and the second carbon fiber prepreg tow is the same as the sum of the heights of the fourth carbon fiber prepreg tow and the fifth carbon fiber prepreg tow.

4. The method for preparing a carbon fiber composite material flat plate joint according to claim 1 or 4, 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-numbered rows and horizontal intervals based on a first laying angle; The fourth carbon fiber prepreg tows are laid in even-numbered rows based on the first laying angle in the grooves spaced apart by the first carbon fiber prepreg tow arrays 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 web preform.

9. A carbon fiber composite material flat plate joint, characterized in that: The method is used to prepare a carbon fiber composite material flat plate joint according to any one of claims 1 to 8.

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