A method for integral molding of composite materials with variable Poisson's ratio

Abstract

This invention discloses a method for the integrated molding of variable Poisson's ratio composite materials, belonging to the field of materials science. The purpose of this invention is to address the current lack of research on the preparation of variable Poisson's ratio composite materials, and the complexity of the preparation process, which prevents integrated molding. The method includes: 1. Cutting and laying prepreg; 2. Preparing laminates; 3. Curing laminates; 4. Fixing laminates; 5. Stretching laminates; 6. Compressing laminates to obtain the variable Poisson's ratio composite material. The variable Poisson's ratio composite material prepared by this invention exhibits strong designability of topological dimensions, a simple method, and high preparation accuracy. The preparation process can be completed by machine, eliminating manual labor and making it simple and efficient. Using this method, integrated molding of materials can be achieved, and the Poisson's ratio can be determined according to requirements. This method enables the preparation of materials with different topological configurations or multiple sizes, demonstrating strong practicality and broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of materials, specifically relating to a method for integral molding of composite materials with variable Poisson's ratio. Background Technology

[0002] Composite sandwich structures, as a type of biomimetic structure, are widely used in aerospace, shipbuilding, and transportation engineering fields due to their ingenious topological configuration combined with the material's performance advantages, such as lightweight, high specific strength, high specific stiffness, corrosion resistance, and fatigue resistance. To further improve the mechanical properties of sandwich materials, many scholars have proposed strengthening methods, such as material strengthening, void filling, multi-level structures, and curved wall design. Among these, curved wall design simply modifies the straight walls of the traditional hexagonal honeycomb structure into curved walls, without introducing new materials, making it the simplest optimization method.

[0003] Poisson's ratio is an elastic constant reflecting the deformation of a material. It is generally believed that almost all materials have a positive Poisson's ratio. Only through structural design can a zero / negative Poisson's ratio be achieved. Negative Poisson's ratio structures exhibit anomalous tensile behavior, thus possessing unique properties different from ordinary materials, such as strong impact resistance and high energy absorption, making them suitable for collision avoidance devices in engineering. Furthermore, positive Poisson's ratio structures have good stability and out-of-plane strength, but they produce severe saddle-shaped deformation when bent, making them unsuitable for curved components in practical applications, such as satellite antennas, space telescopes, and load-bearing cylindrical structures. Zero / negative Poisson's ratio structures can better solve this problem. Therefore, variable Poisson's ratio materials are needed to meet different application scenarios. Currently, research on the preparation of variable Poisson's ratio composite materials is still scarce, and the preparation process is complex and cannot achieve integrated molding. Summary of the Invention

[0004] The purpose of this invention is to address the current lack of research on the preparation of variable Poisson's ratio composite materials, the complexity of the preparation process, and the inability to achieve integrated molding, and to provide a method for integrated molding of variable Poisson's ratio composite materials.

[0005] A method for integral molding of variable Poisson's ratio composite materials is specifically completed according to the following steps:

[0006] I. Cutting and laying of prepreg:

[0007] The ultra-thin unidirectional prepreg is cut according to the design dimensions along the fiber direction and perpendicular to the fiber direction. The cut prepreg is then laid out in a certain arrangement to obtain the laid-out prepreg.

[0008] II. Preparation of laminated plates:

[0009] ① On the prepreg, strips of release fabric are laid alternately in a regular pattern. The width of the strips of release fabric is the same as the width of the prepreg. The arrangement of the release fabric is as follows: starting at the boundary, the length of the release fabric on both sides is a+b, the length of the release fabric in the middle is 2a+b, and they are arranged at intervals of b to obtain the prepreg I with release fabric laid.

[0010] ② On the laid prepreg, strips of release fabric are laid alternately in a regular pattern. The width of the strips of release fabric is the same as the width of the prepreg. The arrangement of the release fabric is as follows: starting at a distance b from the boundary, the length of the release fabric is 2a+b, and they are arranged at intervals of b to obtain the prepreg II with the release fabric laid.

[0011] ③ Alternately stack prepreg I with release fabric and prepreg II with release fabric to obtain laminate;

[0012] 3. Curing of laminates:

[0013] Steel plates are placed on both sides of the laminate, and then cured using an autoclave forming process. The steel plates on both sides are then removed to obtain the cured laminate.

[0014] IV. Fixing the laminated board:

[0015] After curing, stretching dies are installed at intervals on both sides of the outermost layer of the laminate and then fixed.

[0016] V. Tensioning of laminated boards:

[0017] Two round rods are stretched evenly using a stretching machine and then cured and shaped to obtain a curved wall topological structure material.

[0018] VI. Compression of laminated boards:

[0019] Two plates are placed in a direction perpendicular to the stretching direction in step five. The two plates are then used to compress the two sides of the curved wall topology material to the desired shape, and then cured and shaped to obtain a variable Poisson's ratio composite material.

[0020] The present invention has the following beneficial effects:

[0021] I. This invention solves the practical application problems of existing composite materials, enabling structures to meet the needs of planar or curved components. It proposes a stable, reliable, integrally molded composite material preparation method with variable Poisson's ratio. Specifically, it uses unidirectional prepreg of composite materials to lay up and cure in a certain arrangement, and then performs tensile and compressive shaping as needed. The topological dimensions of the variable Poisson's ratio composite material prepared by this method are highly designable, the method is simple, and the preparation accuracy is high. The preparation process can be completed by machine without manual labor, which is simple and efficient.

[0022] Second, the method of this invention can realize the integrated molding of materials, determine the Poisson's ratio according to the requirements, and realize the preparation of materials with different topological configurations or multiple sizes in one method. It has strong practicality and broad application prospects. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the prepreg laying process in step one of Example 1;

[0024] Figure 2 This is a schematic diagram of the method for laying the release fabric on the prepreg in step two of Example 1 and the method for alternately stacking them to form a laminate;

[0025] Figure 3 This is a schematic diagram of the lamination fixing in step four of Example 1;

[0026] Figure 4 This is a schematic diagram of the compression of the laminate in step six of Example 1;

[0027] Figure 5 The positive Poisson's ratio composite material was prepared using the method of Example 1;

[0028] Figure 6 The negative Poisson's ratio composite material was prepared using the method of Example 1;

[0029] Figure 7 The image shows a comparison of the compressive strength of the positive and negative Poisson's ratio carbon fiber composites prepared in Example 1 with that of a metallic material (aluminum foil). Detailed Implementation

[0030] Specific Implementation Method 1: This implementation method describes a method for integral molding of variable Poisson's ratio composite materials, which is specifically completed according to the following steps:

[0031] I. Cutting and laying of prepreg:

[0032] The ultra-thin unidirectional prepreg is cut according to the design dimensions along the fiber direction and perpendicular to the fiber direction. The cut prepreg is then laid out in a certain arrangement to obtain the laid-out prepreg.

[0033] II. Preparation of laminated plates:

[0034] ① On the prepreg, strips of release fabric are laid alternately in a regular pattern. The width of the strips of release fabric is the same as the width of the prepreg. The arrangement of the release fabric is as follows: starting at the boundary, the length of the release fabric on both sides is a+b, the length of the release fabric in the middle is 2a+b, and they are arranged at intervals of b to obtain the prepreg I with release fabric laid.

[0035] ② On the laid prepreg, strips of release fabric are laid alternately in a regular pattern. The width of the strips of release fabric is the same as the width of the prepreg. The arrangement of the release fabric is as follows: starting at a distance b from the boundary, the length of the release fabric is 2a+b, and they are arranged at intervals of b to obtain the prepreg II with the release fabric laid.

[0036] ③ Alternately stack prepreg I with release fabric and prepreg II with release fabric to obtain laminate;

[0037] 3. Curing of laminates:

[0038] Steel plates are placed on both sides of the laminate, and then cured using an autoclave forming process. The steel plates on both sides are then removed to obtain the cured laminate.

[0039] IV. Fixing the laminated board:

[0040] After curing, stretching dies are installed at intervals on both sides of the outermost layer of the laminate and then fixed.

[0041] V. Tensioning of laminated boards:

[0042] Two round rods are stretched evenly using a stretching machine and then cured and shaped to obtain a curved wall topological structure material.

[0043] VI. Compression of laminated boards:

[0044] Two plates are placed in a direction perpendicular to the stretching direction in step five. The two plates are then used to compress the two sides of the curved wall topology material to the desired shape, and then cured and shaped to obtain a variable Poisson's ratio composite material.

[0045] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the ultra-thin unidirectional prepreg mentioned in step one is made by impregnating unidirectional continuous fibers with resin as the matrix; the thickness of the ultra-thin unidirectional prepreg is 0.01–0.03 mm, and the mass fraction of resin in the ultra-thin unidirectional prepreg is 40%–50%; the fibers are carbon fiber, aramid fiber, or glass fiber; and the resin is epoxy resin. Other steps are the same as in Specific Implementation Method One.

[0046] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the arrangement of the prepreg in step one is [0° s / 90° / 0° s The sequence is as follows: 90° represents the long side cut along the fiber direction, 0° represents the long side cut perpendicular to the fiber direction, and s represents any number of layers, one or more. Other steps are the same as in specific implementation method one or two.

[0047] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the release cloth mentioned in step two is polytetrafluoroethylene (PTFE). The other steps are the same as in Specific Implementation Methods One to Three.

[0048] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: in steps 2① and 2, the value range of 'a' is b≤a≤4b, and the value range of 'b' is b≥2mm; in step 2③, the number of layers of prepreg I and prepreg II laid with release fabric in the laminate is the same, both being m layers, where m is the number of unit cells in the stacking direction of the laminate, and m≥1. Other steps are the same as in Specific Implementation Methods One to Four.

[0049] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the curing process in step three uses an autoclave molding process. Specifically, it is completed as follows: A laminated board with steel plates on both sides is wrapped with breathable felt and placed in a sealed bag. The sealed bag is then placed in an autoclave for vacuum heating and pressurization. The heating and pressurization parameters are: 0.1 MPa pressure at 80℃~85℃ for 30min~40min, followed by 0.3 MPa pressure at 130℃~135℃ for 90min~100min. After the process is completed, the pressure is released and the temperature drops to room temperature, thus completing the entire curing process. Other steps are the same as in Specific Implementation Methods One to Five.

[0050] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: the stretching die described in step four consists of two round rods and several sliders that can slide on the round rods; the bottom dimension of the sliders is the same as the dimension of the bonding area of ​​the laminate; the length of the round rods is greater than the length of the laminate, and the diameter d of the round rods is 0.5 to 0.7 of the height D of the sliders. Other steps are the same as in Specific Implementation Methods One through Six.

[0051] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the round rod is made of metal; the slider is also made of metal. The other steps are the same as in Specific Implementation Methods One to Seven.

[0052] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: the curing and shaping method described in step five is: placing the laminate and stretching die at a temperature of 160℃~190℃ for 1h~3h; the curing and shaping method described in step six is: placing the compressed curved wall topology material at a temperature of 160℃~190℃ for 1h~3h. Other steps are the same as in Specific Implementation Methods One to Eight.

[0053] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in that the variable Poisson's ratio composite material mentioned in step six is ​​a positive Poisson's ratio composite material, a zero Poisson's ratio composite material, or a negative Poisson's ratio composite material. The Poisson's ratio changes from positive to zero and then to negative as the degree of compression increases. The other steps are the same as in Specific Implementation Methods One through Nine.

[0054] The beneficial effects of the present invention are verified using the following embodiments:

[0055] Example 1: A method for integral molding of variable Poisson's ratio composite materials, specifically completed according to the following steps:

[0056] I. Cutting and laying of prepreg:

[0057] The ultrathin unidirectional prepreg is cut according to the design dimensions along the fiber direction and perpendicular to the fiber direction. The cut prepreg is then laid out in a specific pattern to obtain the laid-out prepreg. For example... Figure 1 The above;

[0058] In step one, the prepreg is arranged in the order of [0° / 90° / 0°], where 90° represents the long side cut along the fiber direction and 0° represents the long side cut perpendicular to the fiber direction.

[0059] The ultra-thin unidirectional prepreg mentioned in step one is made by impregnating unidirectional continuous fibers with resin as the matrix; the manufacturer is Shandong Lanke New Material Technology Co., Ltd., model 01000, and the fiber weight is 11g / m². 2 Thickness 0.015mm, resin mass fraction 50%;

[0060] II. Preparation of laminated plates:

[0061] ① On the prepreg, strips of release fabric are laid alternately in a regular pattern. The width of the strips of release fabric is the same as the width of the prepreg. The arrangement of the release fabric is as follows: starting at the boundary, the length of the release fabric on both sides is a+b, the length of the release fabric in the middle is 2a+b, and they are arranged at intervals of b to obtain the prepreg I with release fabric laid.

[0062] ② On the prepreg, strips of release fabric are laid alternately in a regular pattern. The width of the strips of release fabric is the same as the width of the prepreg. The arrangement of the release fabric is as follows: starting at a boundary distance b, the length of the release fabric is 2a+b, and they are arranged at intervals of b to obtain the prepreg II with the release fabric laid.

[0063] ③ Alternately stack prepreg I with release lining and prepreg II with release lining to obtain laminate, such as Figure 2 As shown;

[0064] The release cloth mentioned in step two is made of polytetrafluoroethylene, which can prevent the fibers from sticking together during high-temperature curing.

[0065] In steps 2① and 2, the value range of 'a' is a = 8 mm, and the value range of 'b' is b = 2 mm; in step 2③, the number of layers of prepreg I and prepreg II laid with release fabric in the laminate is the same, both being 5 layers.

[0066] 3. Curing of laminates:

[0067] Steel plates are placed on both sides of the laminate, and then cured using an autoclave forming process. The steel plates on both sides are then removed to obtain the cured laminate.

[0068] Step three involves using an autoclave molding process for curing, which is specifically completed according to the following steps:

[0069] Wrap the laminated board with steel plates on both sides with breathable felt, place it in a sealed bag, and then put the sealed bag into a thermostatic jar for vacuum heating and pressurization. The heating and pressurization parameters are: maintain 0.1 MPa pressure at 80℃ for 30 minutes, and then maintain 0.3 MPa pressure at 130℃ for 90 minutes. After the process is completed, release the pressure and let it drop to room temperature. The entire curing process is complete.

[0070] IV. Fixing the laminated board:

[0071] After the laminate has cured, stretching dies are installed and fixed at intervals on both sides of the outermost layer. Figure 3 As shown;

[0072] The stretching die described in step four consists of two round rods and several sliders that can slide on the round rods; the bottom dimension of the sliders is the same as the dimension of the bonding area of ​​the laminate; the length of the round rods is greater than the length of the laminate, and the diameter d of the round rods is 0.5 times the height D of the sliders;

[0073] The round rod is made of metal; the slider is made of metal.

[0074] V. Tensioning of laminated boards:

[0075] Two round rods are stretched evenly using a stretching machine and then cured and shaped to obtain a curved wall topological structure material.

[0076] The curing and shaping method described in step five is as follows: place the laminate and the stretching die at a temperature of 170°C for 1 hour;

[0077] VI. Compression of laminated boards:

[0078] Two plates are placed in a direction perpendicular to the stretching direction in step five. These two plates are then used to compress the two edges of the curved wall topology material to the desired shape, followed by curing and shaping to obtain a variable Poisson's ratio composite material, such as... Figure 4 As shown.

[0079] The curing and shaping method described in step six is ​​as follows: the compressed curved wall topology material is placed at a temperature of 170°C for 1 hour.

[0080] Figure 5 The positive Poisson's ratio composite material was prepared using the method of Example 1;

[0081] Figure 6 The negative Poisson's ratio composite material was prepared using the method of Example 1.

[0082] Comparison of the compressive strength of positive and negative Poisson's ratio carbon fiber composites prepared using this process with that of metallic materials (aluminum foil) Figure 7 As shown. In the low-density range, the compressive strength of the positive Poisson's ratio carbon fiber composite material prepared by this invention is nearly twice that of aluminum foil. In the medium-density range, the compressive strength of the negative Poisson's ratio carbon fiber composite material is higher than that of aluminum foil, demonstrating its performance advantages and broad application prospects in the field of ultra-lightweight and high-strength materials.

Claims

1. A method for integral molding of a variable Poisson's ratio composite material, characterized in that... The method is specifically implemented according to the following steps: I. Cutting and laying of prepreg: The ultra-thin unidirectional prepreg is cut according to the design dimensions along the fiber direction and perpendicular to the fiber direction. The cut prepreg is then laid out in a certain arrangement to obtain the laid-out prepreg. II. Preparation of laminated plates: ① On the prepreg, strips of release fabric are laid alternately in a regular pattern. The width of the strips of release fabric is the same as the width of the prepreg. The arrangement of the release fabric is as follows: starting at the boundary, the length of the release fabric on both sides is a+b, the length of the release fabric in the middle is 2a+b, and they are arranged at intervals of b to obtain the prepreg I with release fabric laid. ② On the laid prepreg, strips of release fabric are laid alternately in a regular pattern. The width of the strips of release fabric is the same as the width of the prepreg. The arrangement of the release fabric is as follows: starting at a distance b from the boundary, the length of the release fabric is 2a+b, and they are arranged at intervals of b to obtain the prepreg II with the release fabric laid. ③ Alternately stack prepreg I with release fabric and prepreg II with release fabric to obtain laminate; In steps 2, ① and ②, the range of values ​​for 'a' is b ≤ a ≤ 4b, and the range of values ​​for 'b' is b ≥ 2mm. In step 2③, the number of layers of prepreg I and prepreg II laid with release fabric in the laminate is the same, both being m layers, where m is the number of unit cells in the stacking direction of the laminate, and m≥1; 3. Curing of laminates: Steel plates are placed on both sides of the laminate, and then cured using an autoclave forming process. The steel plates on both sides are then removed to obtain the cured laminate. IV. Fixing the laminated board: After curing, stretching dies are installed at intervals on both sides of the outermost layer of the laminate and then fixed. V. Tensioning of laminated boards: Two round rods are stretched evenly using a stretching machine and then cured and shaped to obtain a curved wall topological structure material. VI. Compression of laminated boards: Two plates are placed in a direction perpendicular to the stretching direction in step five. The two plates are then used to compress the two sides of the curved wall topology material to the desired shape, and then cured and shaped to obtain a variable Poisson's ratio composite material.

2. The method for integral molding of a variable Poisson's ratio composite material according to claim 1, characterized in that... The ultra-thin unidirectional prepreg mentioned in step one is made by impregnating unidirectional continuous fibers with resin as the matrix; the thickness of the ultra-thin unidirectional prepreg is 0.01~0.03mm, and the mass fraction of resin in the ultra-thin unidirectional prepreg is 40%~50%; the fiber is carbon fiber, aramid fiber or glass fiber; and the resin is epoxy resin.

3. The method for integral molding of a variable Poisson's ratio composite material according to claim 1, characterized in that... The arrangement of the prepreg in step one is [0° s / 90° / 0° s The sequence is defined as follows: 90° represents the long side cut along the fiber direction, 0° represents the long side cut perpendicular to the fiber direction, and s represents any number of layers, one or more.

4. The method for integral molding of a variable Poisson's ratio composite material according to claim 1, characterized in that... The release cloth mentioned in step two is polytetrafluoroethylene.

5. The method for integral molding of a variable Poisson's ratio composite material according to claim 1, characterized in that... Step three involves using an autoclave molding process for curing, which is specifically completed as follows: A laminate with steel plates on both sides is wrapped with breathable felt and placed in a sealed bag. The sealed bag is then placed in an autoclave for vacuum heating and pressurization. The heating and pressurization parameters are: 0.1 MPa pressure at 80℃~85℃ for 30~40 minutes, followed by 0.3 MPa pressure at 130℃~135℃ for 90~100 minutes. After the process is completed, the pressure is released and the temperature drops to room temperature, thus completing the entire curing process.

6. The method for integral molding of a variable Poisson's ratio composite material according to claim 1, characterized in that... The stretching die described in step four consists of two round rods and several sliders that can slide on the round rods; the bottom dimension of the sliders is the same as the dimension of the bonding area of ​​the laminate; the length of the round rods is greater than the length of the laminate, and the diameter d of the round rods is 0.5 to 0.7 of the height D of the sliders.

7. The method for integral molding of a variable Poisson's ratio composite material according to claim 6, characterized in that... The round rod is made of metal; the slider is made of metal.

8. The method for integral molding of a variable Poisson's ratio composite material according to claim 1, characterized in that... The curing and shaping method described in step five is as follows: place the laminate and stretching die at a temperature of 160℃~190℃ for 1h~3h; the curing and shaping method described in step six is ​​as follows: place the compressed curved wall topology material at a temperature of 160℃~190℃ for 1h~3h.

9. The method for integral molding of a variable Poisson's ratio composite material according to claim 1, characterized in that... The variable Poisson's ratio composite material mentioned in step six is ​​a positive Poisson's ratio composite material, a zero Poisson's ratio composite material, or a negative Poisson's ratio composite material.

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