Preparation method of bistable composite material laminated plate with controllable mechanical property
By introducing initial curing curvature and finite element analysis, bistable composite laminates are prepared, which solves the problems of cumbersome and high cost of mechanical performance regulation in the prior art, and achieves simple and fast large-scale mechanical performance adjustment.
Patent Information
- Application Number
- CN202510268098.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-07
- Publication Date
- 2025-08-01
AI Technical Summary
In the prior art, the mechanical properties improvement method of bistable composite laminates is complicated, costly and has a small adjustment range, making it difficult to achieve simple and fast large-scale regulation.
By introducing the initial curing curvature, using orthogonal laminate laying and finite element analysis, a mold with initial curing curvature is prepared, and combined with the high-temperature and high-pressure curing process, the mechanical properties of the bistable composite laminate are adjusted.
It realizes simple and fast large-scale mechanical performance regulation, reduces manufacturing costs, avoids repeated trial and error in traditional methods, and improves preparation efficiency.
Smart Images
Figure CN120409084A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of composite material preparation, and relates to a method for preparing a bistable composite laminate with adjustable mechanical properties. Background Art
[0002] Composite materials are usually composed of two or more different types of components, namely matrix materials and reinforcing materials. The matrix material is the main component, while the reinforcing material is used to increase strength, hardness, and stiffness properties. The bistable composite laminate made therefrom can be affected by external stimuli (such as temperature, stress, electric field, or magnetic field) to achieve a switch from one state to another.
[0003] A bistable laminate refers to a composite laminate having two stable configurations. In 1981, Hyer MW from Virginia Tech first discovered that a cross-ply composite laminate would exhibit bistable characteristics after high-temperature curing. This characteristic is due to the anisotropy of the composite material, with different thermal expansion coefficients in different directions, resulting in large deformations in the laminate due to the action of internal residual thermal stresses after high-temperature curing, presenting two stable configurations, and the curvature directions of the two configurations being opposite.
[0004] Due to the difference in thermal expansion coefficients, an asymmetric bistable laminate can be maintained in any stable configuration without additional energy. When driven by external energy, the bistable laminate can break from one stable state to another, and this process can be achieved through various driving strategies.
[0005] The preparation and regulation of bistable composites is an active research field, and scientists and engineers are constantly seeking new methods and material combinations to meet the requirements of different applications. Currently, the structure mainly has the disadvantage of weak mechanical properties, such as structural bearing capacity, initial stiffness, etc. Currently, common improvement measures include adjusting the ply angle, modifying the geometric dimensions, and embedding metal layers, etc.
[0006] Although there are corresponding methods to improve the mechanical properties of bistable composite laminates, these methods are relatively cumbersome to prepare, have high costs, and have a small adjustment range, and are not suitable for large-scale adjustments and other disadvantages.
[0007] Therefore, how to simply and quickly prepare a bistable composite laminate and regulate its mechanical properties is an urgent problem to be solved. Summary of the Invention
[0008] The object of the present invention is to provide a preparation method of a bistable composite laminate with controllable mechanical properties. By introducing an initial curing curvature, the mechanical properties of the bistable composite laminate can be regulated. This method is simple to prepare and regulate, and can be adjusted within a wide range.
[0009] To achieve the above object, the present invention adopts the following technical solutions: A preparation method of a bistable composite laminate with controllable mechanical properties, wherein the bistable composite laminate is prepared by orthogonal laminate laying. The method comprises the following steps: Step 1: Based on the requirements of the properties of the bistable composite laminate, establish a steady-state analysis model of the bistable composite laminate; Step 2: Solve the design parameters of the bistable composite laminate through the steady-state analysis model; Step 3: Verify the mechanical properties of the bistable composite laminate through simulation; Step 4: Regulate the mechanical properties of the bistable composite laminate by introducing an initial curing curvature. Specifically: Prepare a mold with an initial curing curvature, and according to the above design parameters and in combination with using the mold, carry out a high-temperature and high-pressure curing process on the preliminarily laid laminate to obtain the bistable composite laminate; The mechanical properties of the bistable composite laminate can be regulated by changing the initial curing curvature.
[0010] Further, in the step 1, based on the requirements of the properties of the bistable composite laminate, including the number of steady states, steady-state configuration, sudden load, energy absorption, and geometric dimensions of the composite material of the bistable composite laminate, establish a mechanical model of the bistable composite laminate (i.e., the steady-state analysis model); The specific model of the bistable composite laminate is as follows: Based on the classical laminate theory, Hamilton theory and Rayleigh-Ritz method, establish a mechanical model of an orthogonal bistable composite laminate.
[0011] Further, in the step 2, according to the actual use situation, set the mechanical properties of the bistable laminate, and use the requirements of the properties of the bistable composite laminate (including the number of steady states, steady-state configuration, sudden load, energy absorption, and geometric dimensions of the composite material) as design parameters, and substitute them into the mechanical model of the bistable composite laminate for calculation to solve the design parameters of the structure.
[0012] Further, in the step 3, according to the parameters after design, establish a simulation three-dimensional model, and use the ABAQUS finite element analysis software to carry out simulation on the model for verification.
[0013] Further, in step 4, a metal mold with an initial curing curvature is prepared. During the high-temperature and high-pressure curing process of the laminate, an arc-shaped metal mold with an initial curing curvature is used. The fabricated composite material sample is placed into the mold to introduce an initial curing curvature to the laminate, and then cured and formed in an autoclave to obtain a bistable composite laminate. By changing the initial curing curvature, the stable configurations and mechanical properties of the bistable laminate can be changed.
[0014] Further, the obtaining of the bistable composite laminate specifically includes the following steps: S1: According to the designed dimensions of the bistable composite laminate, prepreg with a certain thickness is cut into appropriate sizes. S2: Before laying the laminate, the metal mold with an initial curing curvature used for laying is thoroughly cleaned with acetone solution to remove surface residues. Subsequently, a release agent is applied to the surface of the mold. S3: The laminate laid in an orthogonal manner is laid on the mold with an initial curing curvature. S4: The mold is placed into an autoclave, and the laminate is subjected to a high-temperature and high-pressure curing process at a predetermined temperature and pressure. S5: The autoclave is depressurized, and the sample is taken out of the mold and cooled at room temperature for a certain period of time to ensure that the laminate is completely cooled, thus obtaining the bistable composite laminate.
[0015] Further, to enable the laminate to have bistable characteristics, after curing is completed, the air compressor is first turned off, the autoclave is depressurized, and the laminate is taken out of the mold and cooled at room temperature. During the cooling process, the laminate deforms, and the bistable composite laminate can be obtained after cooling to room temperature.
[0016] The bistable composite laminate is prepared by laying an orthogonal laminate, that is, by using an asymmetric laying method. Its specific parameters are [0 / 90]n, where n is the ply parameter, 0 and 90 are the laying angles. Specifically, a certain number of carbon fiber layers are laid in the fiber direction of 0°, and the same number of carbon fiber layers are laid in the fiber direction of 90°. The coordinate system used is that the fiber laying direction of 0° is the x-axis, 90° is the y-axis, and the direction perpendicular to the xy plane is the Z-axis, with the coordinate origin being point o.
[0017] Further, the bistable composite is prepared by laying an orthogonal laminate. During the high-temperature curing and forming process, the temperature in the autoclave is adjusted to 180°C, the pressure is adjusted to 0.7 Mpa, and the curing time is set to 3 h.
[0018] Compared with the traditional methods for regulating the mechanical properties of laminates, the beneficial effects of the present invention are: During the preparation of the laminated plate, the mechanical properties of the laminated plate are adjusted by adjusting the initial curing curvature. Compared with the traditional process that relies on adjusting the material formula or complex post-treatment, this method focuses on modifying the curvature parameters in the initial laying stage, and can adjust the mechanical properties of the formed laminated plate in a large range. And because the finite element analysis of the mechanical model is required during the regulation process, the resource consumption of repeated trial and error in the traditional method is avoided, and the manufacturing cost is reduced. Description of the Drawings
[0019] Figure 1 It is a diagram defining the coordinate system of the bistable composite laminated plate; Figure 2 It is a diagram defining the laying method of the bistable composite laminated plate; Figure 3 It is a schematic diagram of the steady-state transformation of the bistable composite laminated plate; Figure 4 It is a flowchart of the finite element analysis of the bistable composite laminated plate; Figure 5 It is a flowchart of the preparation process of the bistable composite laminated plate; Figure 6 It is a schematic diagram of a mold with pre-curvature; Figure 7 It is a curve graph showing the influence of the initial curing curvature on the stiffness of the bistable composite laminated plate; Figure 8 It is a curve graph of the simulation and experimental load-displacement results of the bistable composite laminated plate. Detailed Implementation Manner
[0020] To make the objectives, technical routes and advantages of the present invention clearer, the following further describes the present invention in combination with the drawings in the specification and embodiments. It should be understood that the specific embodiments described herein are only for illustrative purposes of the present invention and are not limited to the present invention.
[0021] The bistable composite laminated plate of the present invention adopts an asymmetric laying, and its specific parameters are [0 / 90]n, where n is the laying parameter, 0 and 90 are the laying angles, as Figure 1 shown.
[0022] The coordinate system adopted by the bistable composite laminated plate of the present invention is that the fiber laying 0° is the x-axis, 90° is the y-axis, the one perpendicular to the xy plane is the Z-axis, and the coordinate origin is the o point, as Figure 2 shown.
[0023] The bistable composite laminate of the present invention is a carbon fiber laminate with an asymmetric layup. When it is prepared by the autoclave curing process, due to the difference in the coefficient of thermal expansion of the prepreg along the fiber direction and the direction perpendicular to the fiber direction, under the action of internal residual thermal stress, the cured laminate obtains a bistable laminate with two stable configurations during the cooling process. The configuration obtained after the laminate finishes cooling is defined as the first stable state of the bistable laminate, and the second stable state refers to another stable configuration after jumping from the first stable state under the action of the external environment, as Figure 3 shown.
[0024] As a carbon fiber composite laminate structure, the orthogonal bistable laminate of the present invention still applies the classical laminate theory. Based on the Hamilton theory and the Rayleigh-Ritz method, a mechanical model of the orthogonal bistable laminate is established.
[0025] The expression of the Hamilton principle is:
[0026] In the formula, L is the Lagrangian equation of the laminate, U is the potential energy of the laminate, and W represents the work done by the external environment on the laminate.
[0027] During the curing and stable state transition processes of the orthogonal bistable laminate of the present invention, large deformations will occur, which leads to the problem of non-convergence easily occurring during the simulation solution process. Therefore, the ABAQUS finite element software is selected to conduct the simulation analysis of the curing and stable state transition of the bistable laminate, as Figure 4As shown below. First, modeling: In the SOLIDWORKS software, use the surface tool to establish the geometric model of the laminated plate and import it into ABAQUS. In the Part module, first divide the geometric model into regions and set it as a Shell. Then, in the Property module, select the composite material laying option and assign the shell laying parameters according to the ply design of the laminated plate. Subsequently, for assembly: In the Assembly module, select Independent to introduce the shell structure and establish the assembly. Mesh the model with the material properties and boundary conditions set, select the S4R mesh type, and set the mesh density to 50×50, which can shorten the calculation time while ensuring accurate calculation. Finally, for static analysis: To simulate the curing and steady-state transition of the laminated plate, the finite element model is set with three analysis steps: Step1 is the thermal curing stage of the laminated plate. First, apply a temperature field of 150 °C to the laminated plate, and then cool it to 25 °C. At the same time, constrain the central axis of the laminated plate; Step2 is to simulate the process of the bistable laminated plate jumping from the first steady state to the second steady state under the action of an external force. First, change the constraint conditions of the laminated plate, change the central axis constraint to simply supported at four nodes, restrict the displacement in the z direction, and apply a displacement load at the center point of the laminated plate to drive the bistable laminated plate to jump; Step3 is to verify the existence of the bistable characteristic. Release the displacement load introduced in Step2. If the laminated plate has bistability, the steady-state configuration still exists after releasing the displacement load, otherwise the laminated plate returns to the initial cured state.
[0028] The experimental preparation process of the bistable composite laminated plate of the present invention is as Figure 5 shown, and the preparation of the orthogonal bistable laminated plate includes the following steps: Step 1: According to the design dimensions of the bistable composite laminated plate, cut the prepreg with a thickness of 0.1 mm (the prepreg is a fiber material pre-impregnated with resin, and the prepreg is the name of a single-layer material) into a size of 100 mm×100 mm. In this process, it is necessary to first place the refrigerated prepreg in a normal temperature environment to warm up, and wait until the condensed water completely disappears before cutting.
[0029] Step 2: Before laying the laminated plate, thoroughly clean the laying mold with acetone solution to remove surface residues. Subsequently, apply a release agent on the surface of the mold with an initial curvature.
[0030] Step 3: Lay it on the mold with a pre-curvature according to the ply of [0° / 90°]. The mold is as Figure 6 shown.
[0031] Step 4: Place the mold in an autoclave and heat the laminated plate at 180 °C under a pressure of 0.7 MPa for 3 hours.
[0032] Step 5: Release the pressure in the autoclave, take out the sample from the mold and cool it at room temperature (25 °C) for 10 minutes to ensure that the laminate is completely cooled. To endow the laminate with bistable characteristics, after the curing is completed, first turn off the air compressor, release the pressure in the autoclave, take out the laminate from the mold and cool it at room temperature. During the cooling process, the laminate deforms, and a bistable composite laminate can be obtained after cooling to room temperature.
[0033] The bistable composite laminate of the present invention can design the snap load and the extreme value of negative stiffness of the bistable composite laminate by adjusting the initial curing curvature, such as Figure 6 shown. Thereby, the strain energy difference can be adjusted.
[0034] For the bistable composite laminate of the present invention, the steady-state mutation load of laminates with different initial curing curvatures is calculated through a theoretical model. Comparing the experimental results with the finite element calculation results, the results are in good agreement, as Figure 7 shown, where k is the initial curing curvature in the figure, and the strain energy gradually increases with the change of the initial curing curvature.
[0035] It can be concluded from the results that by curing the bistable composite laminate using a mold with curvature, an orthotropic laminate with an initial curing curvature can be obtained.
[0036] Comparing the load-displacement curves obtained from the experiments and finite element analysis of the bistable composite laminate of the present invention, as Figure 8 shown, where FEA represents finite element analysis and EXP represents experimental measurement. The laminate with the curvature closest to the finite element analysis calculation value can be selected for the load-displacement experiment.
[0037] The present invention has the following beneficial effects: While maintaining the bistable characteristics, change the stable configuration, snap load and potential energy of the laminate; on the other hand, the thickness and size of the bistable laminate will not be affected by adjusting the initial curvature. During the preparation process of the laminate, by adjusting the initial curing curvature, the mechanical properties of the laminate can be adjusted. Compared with the traditional process that relies on material formula adjustment or complex post-treatment, this method focuses on modifying the curvature parameters in the initial layup stage, and can adjust the mechanical properties of the formed laminate in a large range. Since the finite element analysis of the mechanical model is required during the regulation process, it avoids the resource consumption of repeated trial and error in the traditional method and reduces the manufacturing cost.
[0038] The above content only represents the preferred embodiments of the present invention and should not be regarded as a limitation of the present invention. Any modification, substitution, or improvement of the present invention that conforms to the core idea and principles of the present invention should be regarded as being included within the scope of the patent protection of the present invention.
Claims
1. A preparation method of a bistable composite laminate with controllable mechanical properties, wherein the bistable composite laminate is prepared by laying an orthogonal laminate, and is characterized in that The method includes the following steps: Step 1: Based on the performance requirements of the bistable composite laminate, establish a steady-state analysis model of the bistable composite laminate; Step 2: Solve the design parameters of the bistable composite laminate through the steady-state analysis model; Step 3: Simulate and verify the mechanical properties of the bistable composite laminate; Step 4: Introduce the initial curing curvature to regulate the mechanical properties of the bistable composite laminate. Specifically: Prepare a mold with an initial curing curvature, and according to the above design parameters and in combination with using the mold, carry out a high-temperature and high-pressure curing process on the preliminarily laid laminate to obtain the bistable composite laminate; The mechanical properties of the bistable composite laminate can be regulated by changing the initial curing curvature.
2. The preparation method of a bistable composite laminate with controllable mechanical properties according to claim 1, characterized in that, In the said Step 1, based on the performance requirements of the bistable composite laminate, including the number of steady states, steady-state configuration, sudden load, energy absorption, and geometric dimensions of the composite material, establish a mechanical model of the bistable composite laminate; The mechanical model of the bistable composite laminate is specifically as follows: Based on the classical laminate theory, Hamilton theory, and Rayleigh-Ritz method, establish a mechanical model of the orthotropic bistable composite laminate.
3. The preparation method of a bistable composite laminate with controllable mechanical properties according to claim 2, characterized in that, In the said Step 2, according to the actual usage situation, set the mechanical properties of the bistable laminate, take the requirements of the bistable composite laminate performance as design parameters, and substitute them into the mechanical model of the bistable composite laminate for calculation to solve the design parameters of the structure.
4. The preparation method of a bistable composite laminate with controllable mechanical properties according to claim 3, characterized in that, In the said Step 3, according to the parameters after design completion, establish a simulation 3D model, and use the ABAQUS finite element analysis software to perform simulation on the model for verification.
5. The preparation method of a bistable composite laminate with controllable mechanical properties according to claim 4, characterized in that, The specific process of the said Step 3 is as follows: First, model. In the SOLIDWORKS software, use the surface tool to establish the geometric model of the laminate and import it into ABAQUS. In the Part module, first divide the geometric model into regions and set it as Shell; then in the Property module, select the composite material laying option and assign the shell laying parameters according to the laminate laying design. Subsequently, assemble. In the Assembly module, select Independent to introduce the shell structure and establish an assembly; mesh the model with the material properties and boundary conditions set, select the S4R mesh type, and set the mesh density to 50×50, which can shorten the calculation time while ensuring the calculation accuracy; Finally, for the static analysis, to simulate the curing and steady-state transition of the laminate, three analysis steps are set in the finite element model: Step 1 is the thermal curing stage of the laminate: First, apply a temperature field of 150 °C to the laminate, and then cool it to 25 °C. At the same time, constrain the central axis of the laminate; Step 2 is to simulate the process of the bistable laminate jumping from the first steady state to the second steady state under the action of an external force: First, change the constraint conditions of the laminate, change the central axis constraint to a four-node simply supported one, restrict the displacement in the z direction, and apply a displacement load at the center point of the laminate to drive the bistable laminate to jump; Step 3 is to verify the existence of the bistable characteristic. Release the displacement load introduced in Step 2. If the laminate has bistability, the steady-state configuration still exists after the displacement load is released. Otherwise, the laminate returns to the initial cured state.
6. The preparation method of a bistable composite laminate with controllable mechanical properties according to claim 1, characterized in that, In the said Step 4, prepare a metal mold with an initial curing curvature. For the high-temperature and high-pressure curing process of the laminate, use an arc-shaped metal mold with an initial curing curvature. Put the made composite material sample into the mold to introduce an initial curing curvature to the laminate, and cure it in an autoclave to obtain a bistable composite laminate. By changing the initial curing curvature, the steady-state configuration and mechanical properties of the bistable laminate can be changed.
7. The preparation method of a bistable composite laminate with controllable mechanical properties according to claim 6, characterized in that, The obtaining of the bistable composite laminate specifically includes the following steps: S1: Cut prepreg with a certain thickness into appropriate sizes according to the design dimensions of the bistable composite laminate; S2: Before laying the laminate, use acetone solution to thoroughly clean the metal mold with an initial curing curvature used for laying to remove surface residues; Subsequently, apply a release agent on the surface of the mold; S3: Lay the laminate laid in an orthogonal manner on the mold with an initial curing curvature; S4: Put the mold into an autoclave and carry out a high-temperature and high-pressure curing process on the laminate at a predetermined temperature and pressure; S5: Release the pressure of the autoclave, take out the sample from the mold and cool it at room temperature for a certain time to ensure that the laminate is completely cooled, and thus obtain a bistable composite laminate.
8. The preparation method of a bistable composite laminate with controllable mechanical properties according to claim 7, characterized in that, To make the laminate have bistable characteristics, after curing is completed, first turn off the air compressor, release the pressure of the autoclave, take out the laminate from the mold and cool it at room temperature. During the cooling process, the laminate deforms, and a bistable composite laminate can be obtained after cooling to room temperature.
9. The preparation method of a bistable composite laminate with controllable mechanical properties according to claim 1, characterized in that, The bistable composite laminate is prepared by laying an orthogonal laminate, that is, by using an asymmetric laying. Its specific parameter is [0 / 90]n, where n is the ply parameter, 0 and 90 are the laying angles. Specifically, a certain number of carbon fiber layers are laid in the fiber direction of 0°, and the same number of carbon fiber layers are laid in the fiber direction of 90°. The coordinate system used is that the fiber laying 0° is the x-axis, 90° is the y-axis, the one perpendicular to the xy plane is the Z-axis, and the coordinate origin is point o.
10. A method for preparing a bistable composite laminate with controllable mechanical properties according to claim 1, wherein the bistable composite is prepared by laying an orthogonal laminate, and is characterized in that In the said high-temperature curing and forming, the temperature of the autoclave is adjusted to 180 °C, the pressure is adjusted to 0.7 Mpa, and the curing time is set to 3 h.