Biomimetic lattice reinforced foam sandwich composite structures and methods of design and manufacture

Abstract

This invention discloses a biomimetic grid-reinforced foam sandwich composite material structure and its design and manufacturing method, relating to the field of composite material application and manufacturing technology. The biomimetic grid-reinforced foam sandwich composite material structure includes a composite material panel and an intermediate core layer. The composite material panel includes an upper panel and a lower panel; the intermediate core layer includes a composite material grid structure, foam filler, and embedded metal blocks. This invention uses a geometric topology optimization calculation method to obtain a composite material grid structure with the smallest volume that meets specified load-bearing requirements. This composite material grid structure simultaneously satisfies the requirements of lightest weight and excellent load-bearing performance.

Description

Technical Field

[0001] This invention relates to the field of composite material application and manufacturing technology, and in particular to a biomimetic grid-reinforced foam sandwich composite material structure and its design and manufacturing methods. Background Technology

[0002] With the rapid development of materials science and the aerospace industry, composite materials and composite foam sandwich structures have been widely used due to their advantages such as high specific strength, high specific stiffness, and designability. This invention addresses a composite foam sandwich structure used as a secondary load-bearing structural component in partition connection frames for cylindrical structures such as fuselage sections. Traditional composite foam sandwich structures employ a bottom panel, a woven foam core, and a top panel; however, this method results in weak load-bearing capacity in the foam sandwich area, making it difficult to assemble with other structures within this area. Simultaneously, with the rapid development of the aerospace industry, composite foam sandwich structures are required to integrate lightweight, high-temperature resistance, and structural load-bearing capacity, requirements that current composite foam sandwich structures struggle to meet.

[0003] To address the aforementioned issues, it is essential to provide a novel structural design for a biomimetic grid-reinforced foam sandwich composite material that integrates high-temperature resistance, lightweight load-bearing capacity, and a molding method matching this novel structure, as well as the resulting biomimetic grid-reinforced foam sandwich composite material structure. Summary of the Invention

[0004] The purpose of this invention is to provide a novel biomimetic grid-reinforced foam sandwich composite material structure and its design and manufacturing methods. This biomimetic grid-reinforced foam sandwich composite material structure can simultaneously meet the requirements of lightweight, high temperature resistance, and structural load-bearing capacity.

[0005] To achieve the above objectives, the solution adopted by the present invention is as follows:

[0006] The first aspect of this invention proposes a biomimetic grid-reinforced foam sandwich composite material structure, comprising a composite material panel and an intermediate core layer. The composite material panel includes an upper panel and a lower panel. The intermediate core layer includes a composite material grid structure, foam filler, and a metal embedded block. The foam filler is filled between the grids of the composite material grid structure, and the metal embedded block is filled at the center of the composite material grid structure. The composite material grid structure, foam filler, and metal embedded block are bonded together by adhesive film bonding and local reinforcement with prepreg. The intermediate core layer is located between the upper and lower panels of the composite material panel and is connected to the upper and lower panels by adhesive film bonding.

[0007] Preferably, both the composite material panel and the composite material grid structure are made of carbon fiber reinforced resin matrix composite material, wherein the carbon fiber is high-strength medium-modulus carbon fiber, including T700, T800, T1100, etc., or high-strength high-modulus carbon fiber, including M40J, M55J, etc.; the resin system is made of resin with high temperature resistance, including bismaleimide resin, cyano resin, polyimide, etc.

[0008] Preferably, the foam filler is a high-temperature resistant foam, including high-temperature resistant polymethacrylimide foam, polyimide foam, etc.

[0009] Preferably, the metal embedded block is made of titanium alloy.

[0010] Preferably, the molding material is made of high-temperature resistant adhesive film, such as J-188, J-242, J-271, J-385, J-415, etc.

[0011] A second aspect of this invention proposes a design method for a biomimetic grid-reinforced foam sandwich composite material structure, comprising the following steps:

[0012] 1) Establish a model of the intermediate core layer component, which includes the composite material region and the metal embedded block region and their geometric information;

[0013] 2) In the finite element software, the intermediate core layer component model is meshed;

[0014] 3) For the intermediate core component model, a composite material card is created, which contains the mechanical performance parameters of the composite material, and the composite material card is assigned to the composite material; and a metal material card is created, which contains the mechanical performance parameters of the composite material, and the metal material card is assigned to the metal embedded block; and a binding connection is established between the composite material region and the metal embedded block region.

[0015] 4) Establish the constraint boundary conditions and mechanical load conditions for the intermediate core layer component model. The constraint boundary conditions include the constraint location and constraint direction, and the mechanical load conditions include the loading location and loading force.

[0016] 5) Establish a calculation method to calculate the intermediate core layer component model and verify whether the intermediate core layer component model is set correctly;

[0017] 6) Establish a topology optimization task model and set the topology optimization algorithm; establish topology optimization response parameters, which include objective parameters and constraint functions; establish a topology optimization objective, selecting the objective parameters as the optimization objective; establish topology optimization constraints, selecting the constraint functions as the optimization constraints; establish topology optimization geometric constraints, which include frozen regions and demolding directions; verify the topology optimization task model to check whether the topology optimization task model is established correctly.

[0018] 7) Based on the topology optimization task model, perform topology optimization calculations on the intermediate core layer component model; through this topology optimization calculation, obtain the optimized composite material grid structure, which has the smallest volume and can meet the load-bearing requirements under the mechanical load conditions; and obtain the structural and material information of the foam filler and the metal embedded block;

[0019] 8) Based on the composite grid structure, foam filler and metal embedded block obtained in step 7), establish an intermediate core layer. The geometry of the foam filler is the geometry of the hollow position of the composite grid structure.

[0020] Preferably, the intermediate core layer component model is a quarter-size model of the actual intermediate core layer component.

[0021] Preferably, the finite element software is Abaqus software;

[0022] Preferably, the mesh is a shell element mesh, and the shell element is an S4R linear reduced integral element.

[0023] Preferably, the mechanical performance parameters include the elasticity model and Poisson's ratio.

[0024] Preferably, the calculation method is a solver setting.

[0025] Preferably, the topology optimization algorithm is a general optimization algorithm (based on sensitivity); the optimization objective is to minimize the volume; the optimization constraint is that the stress is less than the strength of the composite material; and the geometric constraint is the location of the composite material's perimeter.

[0026] A third aspect of this invention provides a method for manufacturing a biomimetic grid-reinforced foam sandwich composite material structure, comprising the following steps:

[0027] 1) Lay the prepreg of the lower panel of the composite material panel, and pre-compact it every four layers. After the prepreg is laid, put it in a hot autoclave for curing to obtain the lower panel preform; then grind the burrs off the obtained lower panel preform.

[0028] 2) Fabricating the intermediate core layer based on the data obtained from the design method includes: First, laying prepreg of the composite grid structure, pre-compacting every eight layers, and after the prepreg is laid, pressing and curing it in a press to obtain the composite grid structure; Second, machining the geometric shape of the foam filler using a machining operation machine; Third, covering the metal embedded block with a layer of adhesive film and a layer of carbon cloth prepreg on the surface bonded to the composite grid structure and composite panel, and placing it in the corresponding position of the composite grid structure; Finally, covering the foam filler with a layer of adhesive film and a layer of carbon cloth prepreg on the surface bonded to the composite grid structure and composite panel, and placing it in the corresponding position of the composite grid structure.

[0029] 3) Cover the surface of the central core layer with a layer of adhesive film and place it on the lower panel preform; lay the upper panel prepreg on the surface of the middle core layer, and pre-compact it every four layers;

[0030] 4) After the prepreg is laid in step 3), it is placed in a hot autoclave for curing to obtain a biomimetic grid-reinforced foam sandwich composite material structure.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects:

[0032] This invention provides a novel biomimetic grid-reinforced foam sandwich composite material structure integrating high-temperature resistance, lightweight load-bearing capacity, and structural integrity. The composite material panels of this structure primarily bear in-plane loads, while the core layer, reinforced by a composite grid structure, mainly bears bending, torsional, compressive, and shear loads, serving as the primary load-bearing component. The foam filler, tightly bonded to the composite grid and panels, primarily maintains shape and bears bending loads. Based on the characteristics of the sandwich structure, inserting a thicker, low-density, porous foam core between two high-strength panels can significantly increase the overall bending resistance of the structure with minimal impact on its weight. The core layer achieves localized reinforcement through pre-embedded metal components, providing a rigid substrate for the connection and assembly of other structural components. The pre-embedded metal blocks are made of titanium alloy, whose coefficient of thermal expansion is similar to that of the composite material, reducing the likelihood of debonding due to thermal expansion mismatch during the molding process.

[0033] This invention, during structural design, utilizes geometric topology optimization calculations to obtain a composite material grid structure with the smallest volume that meets specified load-bearing requirements. This composite material grid structure simultaneously satisfies the requirements of lightest weight and superior load-bearing performance. By combining carbon fiber composite panels, a composite material grid structure, high-temperature resistant lightweight woven foam, and embedded metal blocks in a specific manner through co-bonding, a new composite structure is formed. The high-strength fiber composite panel, high-temperature resistant lightweight woven foam, integrally reinforced composite material grid structure, and locally reinforced embedded metal blocks are connected by a high-temperature resistant structural adhesive film, improving the deformation coordination among the high-strength fiber composite panel, composite material grid structure, high-temperature resistant lightweight woven foam, and locally reinforced embedded metal blocks. This results in a novel biomimetic grid-reinforced foam sandwich composite material structure integrating lightweight, high-temperature resistance, and structural load-bearing capacity. Compared to traditional composite foam sandwich structures, this structure has the significant advantages of simultaneously possessing lightweight, high-temperature resistance, and structural load-bearing capacity. In addition, compared with traditional composite foam sandwich structure molding technology, this co-bonding step-by-step autoclave molding process, which is matched with the new biomimetic grid-reinforced foam sandwich composite material structure, solves the problems of loose quality of the lower panel, easy debonding of different material interfaces, and easy collapse of foam in traditional composite foam sandwich structures, while also ensuring the molding quality of the upper panel. Attached Figure Description

[0034] The accompanying drawings are provided for illustrative purposes only, and the proportions of the components in the drawings may not be consistent with the actual product.

[0035] Figure 1 This is a schematic diagram of the biomimetic grid-reinforced foam sandwich composite material structure in the embodiment.

[0036] Figure 2 This is a cross-sectional view of the biomimetic grid-reinforced foam sandwich composite material structure in the embodiment.

[0037] In the figure: 1: lower panel; 2: composite material grid structure; 3: continuous fiber reinforced resin matrix composite interface reinforcement layer; 4: metal embedded block; 5: upper panel.

[0038] Figure 3 This is a flowchart illustrating the design method of the biomimetic grid-reinforced foam sandwich composite material structure in the embodiments.

[0039] Figure 4 This is a schematic diagram of the optimization process of the intermediate core layer in the embodiment.

[0040] Figure 5 This is a flowchart illustrating the manufacturing method of the biomimetic grid-reinforced foam sandwich composite material structure in the embodiment. Detailed Implementation

[0041] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings.

[0042] This embodiment discloses a novel biomimetic grid-reinforced foam sandwich composite material structure, the structure of which is as follows: Figure 1 and Figure 2 As shown, the structure includes a composite material panel and an intermediate core layer. The composite material panel, being relatively thin, primarily bears in-plane loads and consists of an upper panel 2 and a lower panel 1. The intermediate core layer comprises a composite material grid structure 2, foam filler, and embedded metal blocks 4. The composite material grid structure 2, tightly bonded to the panel, primarily bears bending, torsional, compressive, and shear loads, serving as the main load-bearing component. The foam filler, tightly bonded to both the composite material grid 2 and the panel, primarily maintains shape and bears bending loads. The intermediate core layer achieves localized reinforcement through embedded metal blocks 4, thereby providing a rigid substrate for the connection and assembly of other structural components. The foam core material and the composite material panel are connected using adhesive film bonding, while the foam core material and the embedded metal blocks are bonded using adhesive film bonding and localized prepreg reinforcement (see [link to relevant documentation]). Figure 2 The continuous fiber-reinforced resin matrix composite interface reinforcement layer makes the adhesion stronger.

[0043] For material selection, titanium alloy is preferred for the metal embedded blocks. For the composite material fiber system, high-strength, high-strength, medium-modulus carbon fiber is preferred, including T700, T800, and T1100, or high-strength, high-modulus carbon fiber, including M40J and M55J. For the composite material resin system, bismaleimide resin, cyano resin, and polyimide are preferred. For the foam core material, high-temperature resistant foam is preferred, including high-temperature resistant polymethacrylamide foam and polyimide foam. For the structural adhesive mold, high-temperature resistant adhesive film, such as J-188, J-242, J-271, J-385, and J-415, is preferred.

[0044] This embodiment also discloses a design method for a biomimetic grid-reinforced foam sandwich composite material structure, the flowchart of which is shown below. Figure 3 As shown, it includes the following steps:

[0045] Step S101: Establish an intermediate core layer component model, perform calculations on the model, and verify the correctness of the model settings. The intermediate core layer component model includes a composite material region and a metal embedded block region, along with their geometric information. The intermediate core layer component model uses a quarter-scale model of the actual component. The specific process includes the following: In Abaqus finite element software, mesh the intermediate core layer component model using shell elements (S4R linear reduced integral elements). Establish a composite material card containing the composite material's mechanical property parameters (elasticity model, Poisson's ratio), and assign the composite material card to the composite material; the composite material is a carbon fiber reinforced resin matrix composite. Establish a metal material card containing the composite material's mechanical property parameters (elasticity model, Poisson's ratio), and assign the metal material card to the metal embedded block; the metal material is a titanium alloy. Establish a connection, which is a binding connection between the composite material region and the metal embedded block region. Establish constraint boundary conditions and mechanical load conditions for the intermediate core layer component model. The constraint boundary conditions include constraint location and constraint direction, and the mechanical load conditions include loading location and loading force. The mechanical load conditions represent the design bearing requirements that the intermediate core layer component must meet. Establish a calculation method, which is a solver setting. Perform calculations on the intermediate core layer component model to verify the correctness of the model settings.

[0046] Step S102: Establish a topology optimization task and set a topology optimization algorithm; the topology optimization algorithm is a general optimization algorithm (based on sensitivity). Establish topology optimization response parameters, which include objective parameters and constraint functions. Establish a topology optimization objective, selecting the objective parameters as the optimization objective; the optimization objective is to minimize volume. Establish topology optimization constraints, selecting the constraint functions as optimization constraints; the constraint condition is that the stress is less than the composite material strength. Establish topology optimization geometric constraints, including frozen areas, demolding directions, etc., which are the peripheral positions of the composite material. Verify the topology optimization model to check if the topology optimization model is established correctly; perform topology optimization calculations on the intermediate core layer component model; through topology optimization calculations, obtain the optimized composite material grid structure, which has the smallest volume and can meet the load-bearing requirements under the specified load conditions; and simultaneously obtain the structural and material information of the foam filler and the metal embedded block. The optimization process is as follows: Figure 4 As shown, the final geometry is obtained by topology optimization from the initial geometry.

[0047] Step S103: Establish an intermediate core layer, which includes the composite material grid structure obtained in step S102, foam filler, and metal embedded block. The geometry of the foam filler is the geometry of the hollow position in the composite material grid structure.

[0048] This embodiment also discloses a novel method for manufacturing a biomimetic grid-reinforced foam sandwich composite material structure, the flowchart of which is shown below. Figure 5 As shown, it includes the following steps:

[0049] 1) To fabricate the optimized composite material grid structure described in step S102, a prepreg of the composite material grid structure is laid. Pre-compaction is performed every 8 layers. After the prepreg is laid, it is placed in a press for pressure curing to obtain the composite material grid structure. The composite material used is T800 carbon fiber reinforced bismaleimide resin-based composite material.

[0050] 2) Molding of the composite material lower panel: The composite material lower panel prepreg is laid on the mold according to a certain layup ratio. Pre-compaction is performed every 4 layers until all prepreg is laid. The composite material is T800 carbon fiber reinforced bismaleimide resin-based composite material.

[0051] 3) Place the laid prepreg material of the lower panel into an autoclave for curing to obtain the lower panel preform;

[0052] 4) Demold and remove burrs from the obtained lower panel preform;

[0053] 5) Lay out the composite material grid structure described in step 1.

[0054] 6) To fabricate the foam filler described in step S103, the geometric shape of the foam filler is machined. A layer of adhesive film and a layer of carbon fiber prepreg are applied to the surface where the metal embedded block is bonded to the composite material grid structure and the composite material panel, and then it is placed in the corresponding position on the composite material grid structure. A layer of adhesive film and a layer of carbon fiber prepreg are applied to the surface where the foam filler is bonded to the composite material grid structure and the composite material panel, and then it is placed in the corresponding position on the composite material grid structure. The foam filler is selected from high-temperature resistant polymethacrylimide foam; the metal embedded block is selected from titanium alloy.

[0055] 7) Lay a layer of adhesive film on the surface of other lower panel prefabricated bodies where no intermediate core material is placed; the adhesive film is selected as high temperature resistant structural adhesive film J-188.

[0056] 8) Lay the top panel prepreg on the surface of the adhesive film described in step 7, and pre-compact it every 4 layers until the prepreg is fully laid;

[0057] 9) Place the completed lower panel preform, intermediate core material, and upper panel prepreg into a hot autoclave for curing to obtain a biomimetic grid-reinforced foam sandwich composite material structure.

[0058] Testing showed that the biomimetic grid-reinforced foam sandwich composite material structure designed and prepared in this embodiment has a bending stiffness of 1.17 × 10⁻⁶. 4 N·M 2 While maintaining rigidity, the weight of the entire structure was reduced from 4.98 kg to 2.07 kg, a reduction of 58.4%.

[0059] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention should be covered within the protection scope of the present invention, which is defined by the claims.

Claims

1. A design method for a biomimetic grid-reinforced foam sandwich composite material structure, characterized in that, The biomimetic grid-reinforced foam sandwich composite material structure includes a composite material panel and an intermediate core layer. The composite material panel includes an upper panel and a lower panel. The intermediate core layer includes a composite material grid structure, foam filler, and a metal embedded block. The foam filler is filled between the grids of the composite material grid structure, and the metal embedded block is filled at the center of the composite material grid structure. The composite material grid structure, foam filler, and metal embedded block are bonded together using adhesive film bonding and local reinforcement with prepreg. The intermediate core layer is located between the upper and lower panels of the composite material panel and is connected to the upper and lower panels using adhesive film bonding. The design method includes the following steps: 1) Establish a model of the intermediate core layer component, which includes the composite material region and the metal embedded block region and their geometric information; 2) In the finite element software, the intermediate core layer component model is meshed; the finite element software is Abaqus software; the mesh adopts shell element mesh, and the shell element is S4R linear reduced integral element; 3) For the intermediate core component model, a composite material card is created, which contains the mechanical performance parameters of the composite material, and the composite material card is assigned to the composite material; and a metal material card is created, which contains the mechanical performance parameters of the composite material, and the metal material card is assigned to the metal embedded block; and a binding connection is established between the composite material region and the metal embedded block region. 4) Establish the constraint boundary conditions and mechanical load conditions for the intermediate core layer component model. The constraint boundary conditions include the constraint location and constraint direction, and the mechanical load conditions include the loading location and loading force. 5) Establish a calculation method to calculate the intermediate core layer component model and verify whether the intermediate core layer component model is set correctly; 6) Establish a topology optimization task model and define a topology optimization algorithm; establish topology optimization response parameters, including objective parameters and constraint functions; establish a topology optimization objective, selecting the objective parameters as the optimization objective; establish topology optimization constraints, selecting the constraint functions as the optimization constraints; establish topology optimization geometric constraints, including frozen regions and demolding directions; verify that the topology optimization task model is correctly established; the topology optimization algorithm is a general optimization algorithm based on sensitivity; the optimization objective is minimum volume; the optimization constraint is stress less than the composite material strength; the geometric constraint is the perimeter of the composite material. 7) Based on the topology optimization task model, perform topology optimization calculations on the intermediate core layer component model; through this topology optimization calculation, obtain the optimized composite material grid structure, which has the smallest volume and can meet the load-bearing requirements under the mechanical load conditions; and obtain the structural and material information of the foam filler and the metal embedded block; 8) Based on the composite grid structure, foam filler and metal embedded block obtained in step 7), establish an intermediate core layer. The geometry of the foam filler is the geometry of the hollow position of the composite grid structure.

2. The design method as described in claim 1, characterized in that, The intermediate core component model is a quarter-sized model of the actual intermediate core component.

3. The design method as described in claim 1, characterized in that, The mechanical performance parameters include the elasticity model and Poisson's ratio.

4. The design method as described in claim 1, characterized in that, The calculation method is set by the solver.

5. The design method as described in claim 1, characterized in that, The manufacturing method of the biomimetic grid-reinforced foam sandwich composite material structure includes the following steps: 1) Lay the prepreg of the lower panel of the composite material panel, and pre-compact it every four layers. After the prepreg is laid, put it in a hot autoclave for curing to obtain the lower panel preform; then grind the burrs off the lower panel preform. 2) Fabricating an intermediate core layer based on the design method described in any one of claims 1 to 4, comprising: first, laying prepreg of the composite grid structure, pre-compacting every eight layers, and after the prepreg is laid, pressing and curing it in a press to obtain the composite grid structure; second, machining the geometric shape of the foam filler using a machining operation machine; third, covering the metal embedded block with a layer of adhesive film and a layer of carbon cloth prepreg bonded to the composite grid structure and composite panel, and placing it in the corresponding position of the composite grid structure; finally, covering the foam filler with a layer of adhesive film and a layer of carbon cloth prepreg bonded to the composite grid structure and composite panel, and placing it in the corresponding position of the composite grid structure; 3) Cover the surface of the central core layer with a layer of adhesive film and place it on the lower panel preform; lay the upper panel prepreg on the surface of the middle core layer, and pre-compact it every four layers; 4) After the prepreg is laid in step 3), it is placed in an autoclave for curing to obtain a biomimetic grid-reinforced foam sandwich composite material structure.

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