A method for preparing a sandwich structure composite material based on grid-reinforced foam

Abstract

The invention provides a method for preparing a sandwich structure composite material based on grid-reinforced foam, comprising the following steps: laying foam blocks at regular intervals on a mold according to a structural design, with adjacent foam blocks having the same spacing and being parallel to each other; flatly laying a cut first dry fiber cloth on the neatly laid foam blocks at regular intervals; laying foam blocks in reverse on the first dry fiber cloth and between adjacent foam blocks laid in the regular direction, and squeezing the foam blocks into the gaps between adjacent foam blocks laid in the regular direction from top to bottom; preparing a unidirectional grid structure reinforced foam board by adopting an LCM molding process; cutting the unidirectional grid structure reinforced foam board according to the structural design and perpendicular to the grid structure direction to obtain strip-shaped unidirectional grid structure reinforced foam blocks; repeating the above steps to prepare a bidirectional grid structure reinforced foam board; laying fiber cloth on the upper and lower surfaces of the unidirectional grid structure reinforced foam board or the bidirectional grid structure reinforced foam board, and preparing a sandwich structure composite material based on grid-reinforced foam by adopting an LCM molding process.

Description

Technical Field

[0001] The present invention relates to the field of sandwich structure composite material preparation methods, and in particular to a method for preparing a sandwich structure composite material based on grid-reinforced foam, namely, a unidirectional grid structure reinforced foam sandwich composite material and a bidirectional grid structure reinforced foam sandwich composite material. Background Art

[0002] Traditional foam sandwich composite materials are composed of upper and lower composite panels with high strength and large modulus and low-density foam sandwich materials with low strength and small modulus between the upper and lower panels. They have high specific strength, specific stiffness and excellent impact resistance. In addition, by selecting the type of foam, traditional foam sandwich composite materials can achieve good wave absorption, fire prevention, heat insulation, sound insulation, energy absorption and other functions. Therefore, traditional foam sandwich composite materials have become a typical structural and functional integrated material and have been widely used in rail transportation, high-speed trains, aerospace, shipbuilding and marine engineering and other fields. However, with the continuous improvement of the structural performance requirements of foam sandwich composite materials in engineering applications, traditional foam sandwich composite materials can no longer meet the needs. The composite grid structure is introduced into the core material foam of the traditional foam sandwich composite material to construct a new type of sandwich structure composite material-a sandwich structure composite material based on grid-reinforced foam, that is, a grid structure reinforced foam sandwich composite material, the main part of which is a traditional foam sandwich composite material, and the reinforcement part is a composite grid structure. Therefore, the grid structure reinforced foam sandwich composite material integrates the respective advantages of traditional foam sandwich composite materials and composite grid structures. It not only retains the advantages of traditional foam sandwich composite materials such as lower density, higher strength, higher modulus, impact resistance, and high energy absorption, but also gives full play to the excellent mechanical properties of composite grid structures such as high strength and high modulus. That is: under the premise of a slight increase in the overall density, the mechanical properties of the grid structure reinforced foam sandwich composite material such as flat compression, lateral pressure, bending, shear, and impact resistance are significantly improved.

[0003] Grid structure reinforced foam sandwich composite materials are divided into unidirectional grid structure reinforced foam sandwich composite materials and bidirectional grid structure reinforced foam sandwich composite materials. Unidirectional grid structure reinforced foam sandwich composite materials achieve 2D reinforcement effect in X / Z direction or Y / Z direction. Bidirectional grid structure reinforced foam sandwich composite materials are a typical grid structure reinforced foam sandwich composite materials, which achieve 3D reinforcement effect in three directions of X / Y / Z. Compared with unidirectional grid structure reinforced foam sandwich composite materials, bidirectional grid structure reinforced foam sandwich composite materials have better mechanical properties such as flat pressure, lateral pressure, bending, shearing, impact resistance, and instability resistance.

[0004] There are significant differences in the spatial structural forms between the unidirectional grid structure reinforced foam sandwich composite material and the bidirectional grid structure reinforced foam sandwich composite material. For the unidirectional grid structure reinforced foam sandwich composite material, due to the introduction of the composite grid structure, the foam core board that was originally a whole is divided into discrete foam core blocks. When preparing the preform of the unidirectional grid structure reinforced foam sandwich composite material, the biggest difficulty is that the grid structure uses dry fiber fabrics to intersperse between discrete foam core blocks in a wavy shape. The foam core blocks cannot be accurately laid and fixed at all, and the overall relative stability of the foam core blocks and the dry fiber cloth cannot be guaranteed. For the bidirectional grid structure reinforced foam sandwich composite material, the composite grid structure is distributed in the longitudinal and transverse directions of the surface and extends to the upper and lower panels in the thickness direction, presenting a criss-cross 3D mesh structure. The foam core board that was originally a whole in the traditional foam sandwich composite material is divided into a discrete foam core block by this mesh structure. There are two difficulties in preparing the sandwich preform of the bidirectional grid structure reinforced foam sandwich composite material. One is that it is difficult to accurately arrange and fix the huge number of foam blocks, and the other is that it is difficult to complete the laying of the dry fiber fabric for the grid structure in the vertical and horizontal directions. Whether it is a unidirectional grid structure reinforced foam sandwich composite material or a bidirectional grid structure reinforced foam sandwich composite material, they are faced with technical difficulties such as the difficulty of efficiently and accurately laying and fixing the discrete foam core blocks "cut" by the grid structure, the difficulty of accurately controlling the shape and thickness of the grid structure, and the difficulty of accurately controlling the size and stability of the preform, which leads to the inability to control the batch stability, quality consistency, dimensional accuracy, and apparent quality of the product.

[0005] Grid structure reinforced foam sandwich composite material is a new type of composite sandwich structure. There is currently no public, complete, low-cost, high-precision, and high-efficiency molding process solution. The invention patent "Lattice Reinforced Composite Sandwich Structure" with the authorization announcement number CN101067343B is prepared by cutting along the thickness direction of the core material and filling the gap position with resin or dry fiber cloth, and the lattice reinforced composite sandwich structure is prepared by vacuum infusion process, wherein the lattice is a resin cast body or a fiber reinforced composite material, and the fiber reinforced composite lattice reinforcement effect is much better than the resin cast body lattice. However, due to the soft texture of the dry fiber cloth, it is difficult to control the filling amount of the fiber cloth in the gap between the core materials, and the fiber cloth is very easy to accumulate and bend under vacuum pressure, resulting in the fiber volume fraction and quality consistency of the fiber reinforced composite lattice difficult to accurately control, which will greatly reduce the lattice reinforcement effect and even significantly increase the discreteness of the performance of the lattice reinforced composite sandwich structure. The invention patent "A bidirectional corrugated lattice reinforced composite sandwich structure" with the authorization announcement number CN109318541B, is a bidirectional corrugated lattice reinforced composite sandwich structure obtained by forming a bidirectional reinforced core material with a unidirectional corrugated plate and multiple lattices in the corrugations in the unidirectional corrugated plate, and then bonding the upper and lower panels. The bidirectional reinforced sandwich structure is a hollow structure, and the hollow part can be filled with foam, glass beads and other fillers. This preparation method firstly requires prefabricating the one-way corrugated board in advance; secondly, the lattice is obtained by processing the one-way corrugated board and is a discrete entity; thirdly, the lattice is fixed to the one-way corrugated board, the upper and lower panels and the bidirectional reinforced core material by resin bonding, which will bring the following problems: (1) The one-way corrugated board is a thin-walled structure. If the size is increased, it will inevitably lead to problems such as warping and deformation, so the process cannot be scaled up; (2) The lattice is a discrete entity, and it is a major technical challenge to achieve precise and uniform arrangement on the one-way corrugated board; (3) The lattice is fixed to the one-way corrugated board by resin bonding, and the number of lattices is large, which will inevitably lead to problems such as low preparation efficiency and uncontrollable quality consistency.

[0006] In addition, in the molding process of the prior art, either the manufacturing cost is low but the quality consistency is poor, or the quality consistency is good but the manufacturing cost is high, and there is a common problem of low molding efficiency. According to public information, Nanjing University of Technology in China has proposed an integrated overall molding process to prepare a bidirectional grid structure reinforced foam sandwich composite material, that is: first lay the lower panel, then wrap the glass fiber cloth on the six sides of the foam block by manual winding, and tie it with fiber bundles. Each foam block needs to be treated in this way, and then these foam blocks covered with glass fiber cloth are neatly arranged on the lower panel in sequence, and then the upper panel is laid, and finally the whole is formed by VARI (vacuum assisted resin infusion) process. Beijing Institute of Technology proposed a molding scheme for a bidirectional grid structure reinforced foam sandwich composite material based on the VARI process, that is: first, the foam is enhanced in one direction by manually laying the preform, and then the grid is reinforced and the foam is processed and the grid is reinforced twice in the vertical direction, and finally the upper and lower panels are laid and formed as a whole by the VARI process. Both of the above methods have successfully prepared grid structure reinforced foam sandwich composite materials. The advantages are simple operation, low preparation cost and low process risk. The disadvantages are that the thickness and shape of the grid structure, the spacing between foam blocks, and the stability of the prepared product batches, quality consistency, dimensional accuracy, and apparent quality cannot be controlled, and the molding process is difficult to scale up. At the same time, the probability of defects such as resin enrichment induced by the uneven spacing between adjacent foam blocks will increase significantly. At present, there are also laboratory-level unidirectional grid structure reinforced foam sandwich composite materials with grid structure cross-sections of rectangular, trapezoidal, triangular and other shapes prepared by VARTM (vacuum assisted resin transfer molding) molding process, which have good quality stability and small performance discreteness. However, the size of the VARTM mold must also be increased accordingly, increasing the complexity of the mold, which ultimately leads to a significant increase in the manufacturing cost based on the VARTM molding process and a significant increase in the difficulty of process scale-up. Summary of the invention

[0007] In view of this, the present invention aims to propose a preparation method of a sandwich structure composite material based on grid reinforced foam, namely, a unidirectional grid structure reinforced foam sandwich composite material and a bidirectional grid structure reinforced foam sandwich composite material, so as to solve the problems of high cost, low precision and efficiency of grid structure reinforced foam sandwich composite materials in the prior art.

[0008] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0009] A method for preparing a sandwich structure composite material based on grid-reinforced foam, specifically comprising the following steps:

[0010] (1) Positive placement and fixation of foam blocks. According to the structural design, the foam blocks are placed in the mold in a positive and spaced manner and fixed with positioning blocks / limiting blocks. The spacing between adjacent foam blocks is the same and they are parallel to each other.

[0011] (2) Laying the first dry fiber cloth. Lay the cut first dry fiber cloth evenly on the neatly laid foam blocks at regular intervals in the positive direction.

[0012] (3) Reverse laying of foam blocks: On the first dry fiber cloth, foam blocks are reversely laid between adjacent forward-laid foam blocks, and are squeezed from top to bottom into the gaps between adjacent forward-laid foam blocks.

[0013] (4) Preparation of unidirectional grid structure reinforced foam board. After the above unidirectional grid structure reinforced foam board preform is prepared, the unidirectional grid structure reinforced foam board is prepared by using typical LCM molding processes such as VARI, RTM, VARTM, etc. After the first dry fiber cloth is formed, the unidirectional grid structure is obtained.

[0014] (5) Surface treatment of one-way grid structure reinforced foam board: The surface of the one-way grid structure reinforced foam board is polished with 200-400 mesh sandpaper, then wiped clean with alcohol or acetone and dried.

[0015] (6) Processing of unidirectional grid structure reinforced foam board. The prepared unidirectional grid structure reinforced foam board is processed according to the structural design, that is, the unidirectional grid structure reinforced foam is cut perpendicular to the grid structure direction, thereby obtaining a strip-shaped unidirectional grid structure reinforced foam block.

[0016] (7) Forward laying and fixing of unidirectional grid structure reinforced foam blocks. According to the structural design, the unidirectional grid structure reinforced foam blocks are laid forward and spaced on the mold in sequence, and fixed with positioning blocks / limiting blocks. The spacing between adjacent unidirectional grid structure reinforced foam blocks is the same and they are parallel to each other.

[0017] (8) Laying the second dry fiber cloth. Lay the cut second dry fiber cloth evenly on the neatly laid unidirectional grid structure reinforced foam blocks in the forward direction.

[0018] (9) Reverse laying of unidirectional grid structure reinforced foam blocks: On the second dry fiber cloth, unidirectional grid structure reinforced foam blocks are reversely laid between adjacent forward-laid unidirectional grid structure reinforced foam blocks, and squeezed from top to bottom into the gaps between adjacent forward-laid unidirectional grid structure reinforced foam blocks.

[0019] (10) Preparation of bidirectional grid structure reinforced foam board. After the bidirectional grid structure reinforced foam board preform is prepared, a typical LCM molding process such as VARI, RTM, VARTM, etc. is used to prepare the bidirectional grid structure reinforced foam board, and the second dry fiber cloth is formed into a bidirectional grid structure.

[0020] (11) Surface treatment of the bidirectional grid structure reinforced foam board. The surface of the bidirectional grid structure reinforced foam board is polished with 200-400 mesh sandpaper, then wiped clean with alcohol or acetone and dried.

[0021] (12) Laying down the lower panel. Determine the number of layers of fiber fabric to be laid based on the target thickness of the lower panel and the selected fiber fabric type; determine the size of the cut fiber fabric based on the plane size of the grid-reinforced foam, i.e., the unidirectional grid structure reinforced foam board or the bidirectional grid structure reinforced foam board. The fiber fabric size is 5 mm to 100 mm larger than the plane size of the grid-reinforced foam. Then, lay the fiber fabric on the mold according to the laying design.

[0022] (13) Laying of grid-reinforced foam. Lay grid-reinforced foam on the lower panel.

[0023] (14) Laying of the upper panel. Determine the number of layers of fiber fabric required based on the target thickness of the upper panel and the selected fiber fabric type; cut the fiber fabric to the same size as the fiber fabric for the lower panel, and then lay the fiber fabric on the grid-reinforced foam according to the layup design.

[0024] (15) Integral molding: After the preform of the grid structure reinforced foam sandwich composite material is prepared, it is integrally molded by using a typical LCM molding process such as VARI, RTM, VARTM, etc.

[0025] For a unidirectional grid structure reinforced foam sandwich composite material, except for steps (6)-(11), the remaining steps are performed in sequence; for a bidirectional grid structure reinforced foam sandwich composite material, all the steps are performed in sequence.

[0026] The foam block is a foaming material such as polyvinyl chloride (PVC), polymethacrylimide (PMI), polyethylene terephthalate (PET), polyurethane (PU), polyimide (PI), etc., with a density of ≤400kg / m3 and a length of 200mm-4000mm; the cross-sectional geometric shape of the foam block 1 is determined according to demand and structural design, and simple geometric shapes such as rectangle, trapezoid, triangle, etc. can be selected, and other shapes can also be selected; compared with the design value, the cross-sectional dimension tolerance of the foam block is -0.5mm-0.5mm, and the spacing tolerance between adjacent foam blocks is -0.5mm-0.5mm; the number of foam blocks 1 is ≥2N+1 (1≤N≤100 and N is an integer).

[0027] The first dry fiber cloth and the second dry fiber cloth are dry fiber fabrics of glass fiber, carbon fiber, carbon / glass hybrid fiber, quartz fiber, Kevlar fiber, ultra-high molecular weight polyethylene fiber, PBO fiber, etc., with a surface density of ≥100g / m2. The fiber fabric types of the first dry fiber cloth and the second dry fiber cloth can be the same or different. The thickness of the first dry fiber cloth and the second dry fiber cloth are independent of each other, ranging from 0.1mm to 10mm.

[0028] The length of the one-way grid structure reinforced foam block is 200mm-4000mm, which is constrained by the size of the one-way grid structure reinforced foam board; the thickness of the one-way grid structure reinforced foam block is 0-10mm greater than the thickness of the one-way grid structure reinforced foam board; the cross-sectional geometry of the one-way grid structure reinforced foam block is determined according to demand and structural design, and simple geometric shapes such as rectangle, trapezoid, triangle, etc. can be selected, and other shapes can also be selected, which are independent of the foam block; compared with the design value, the cross-sectional dimension tolerance of the one-way grid structure reinforced foam block is -0.5mm-0.5mm; the number of one-way grid structure reinforced foam blocks is ≥2N+1 (1≤N≤100 and N is an integer), which is constrained by the size of the one-way grid structure reinforced foam board.

[0029] The fiber fabrics used for the lower panel and the upper panel are dry fiber fabrics such as glass fiber, carbon fiber, carbon / glass hybrid fiber, quartz fiber, Kevlar fiber, ultra-high molecular weight polyethylene fiber, PBO fiber, etc., with a surface density ≥100g / m2; the thickness, laying method, and type of fiber fabric used of the lower and upper panels are independent of each other.

[0030] The cross section of the positioning block / limiting block is the same as that of the foam block, and the cross section of the positioning block / limiting block is the same as that of the one-way grid structure reinforced foam block.

[0031] Compared with the prior art, the method for preparing the sandwich structure composite material based on grid-reinforced foam according to the present invention has the following advantages:

[0032] First, by compounding the foam block with the unidirectional grid structure, the unidirectional grid structure reinforced foam is precisely prepared; on the basis of the above, the unidirectional grid structure reinforced foam is processed in a direction perpendicular to the unidirectional grid structure, and the unidirectional grid structure reinforced foam preparation process is repeated to achieve the precise molding of the bidirectional grid structure reinforced foam. Second, the grid reinforced foam, i.e., the unidirectional grid structure reinforced foam board or the bidirectional grid structure reinforced foam board, can be prefabricated in batches, and can be cut, spliced, and bonded like ordinary foam core materials, meeting the low-cost and high-efficiency molding requirements of large-size grid structure reinforced foam sandwich composite materials. Third, the proposed scheme of first preparing the grid reinforced foam and then integrally molding the grid structure reinforced foam sandwich composite material not only effectively solves the technical difficulties faced in the precise molding of the grid reinforced foam, but also realizes the low-cost, high-precision, and high-efficiency molding of the grid structure reinforced foam sandwich composite material. Fourth, the auxiliary tooling for molding the unidirectional grid structure reinforced foam board and the bidirectional grid structure reinforced foam board can be reused and universal, and the latter can be obtained by repeating the preparation steps of the former, thereby greatly reducing the preparation cost and significantly improving the molding efficiency. Fifth, through precise control of the grid-reinforced foam, the problems of the difficulty in precisely controlling the size of the preform during the molding process of the grid-structure reinforced foam sandwich composite material, as well as the overall stability, quality consistency, and apparent quality of the product are fundamentally solved.

[0033] In addition, the preparation method of the present invention achieves low-cost, high-precision and high-efficiency preparation of grid structure reinforced foam sandwich composite materials by first molding the grid reinforced foam, that is, accurately molding the unidirectional / bidirectional grid structure reinforced foam, and then integrally molding the preform, that is, according to the technical solution of the conventional molding method of the composite sandwich structure in which the upper and lower panels and the grid reinforced foam are integrated, thereby solving the problem that there is no low-cost, high-precision and high-efficiency molding solution for grid structure reinforced foam sandwich composite materials so far. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A side view of the foam block or the one-way grid structure reinforced foam block according to the present invention;

[0035] Figure 2 An axial view of the foam block or the one-way grid structure reinforced foam block according to the present invention;

[0036] Figure 3 It is a schematic diagram of a method for preparing the unidirectional grid structure reinforced foam sandwich composite material of the present invention;

[0037] Figure 4 Schematic diagram of the cross section of the unidirectional grid structure reinforced foam block of the present invention, (a) a schematic diagram of the transverse cross section, (b) a schematic diagram of the longitudinal cross section;

[0038] Figure 5 A top view of the one-way grid structure reinforced foam block of the present invention;

[0039] Figure 6 It is a schematic diagram of a method for preparing a bidirectional grid structure reinforced foam sandwich composite material according to the present invention;

[0040] Figure 7 Schematic diagram of the cross section of the bidirectional grid structure reinforced foam block of the present invention, (a) a schematic diagram of the transverse cross section, (b) a schematic diagram of the longitudinal cross section;

[0041] Figure 8 This is a top view of the bidirectional grid structure reinforced foam block described in the present invention.

[0042] Description of reference numerals:

[0043] 1-foam block, 3-first dry fiber cloth, 4-unidirectional grid structure reinforced foam board, 5-unidirectional grid structure, 6-unidirectional grid structure reinforced foam block, 8-second dry fiber cloth, 9-bidirectional grid structure reinforced foam board, 10-bidirectional grid structure, 11-lower panel, 13-upper panel, 14-mold DETAILED DESCRIPTION

[0044] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the drawings. It should be noted that the positioning blocks or limit blocks in this embodiment are designed with reference to the positioning blocks or limit blocks in the inventor's prior 202011309934.5 and 202110699161.4.

[0045] Embodiment 1

[0046] like Figures 1 to 5 As shown, Example 1 is a method for preparing a unidirectional grid structure reinforced foam sandwich composite material.

[0047] The foam core material is 60kg / m3 PVC foam; the foam block 1 is 950mm long, 40mm wide, and 20mm high, with a number of 31, and the spacing between adjacent foam blocks 1 is 40.4mm; the dry fiber cloth 3 used in the unidirectional grid structure 5 is a twill carbon fiber fabric with a surface density of 198g / m2, with a number of 1 layer; the dry fiber cloth used in the lower panel 11 and the upper panel 13 is an E glass fiber lattice cloth with a surface density of 400g / m2, with a number of 8 layers. Therefore, the unidirectional grid structure reinforced foam board 4 is 1246mm long, 950mm wide, and 20mm high. In addition, the cross section of the positioning block / limiting block is the same as that of the foam block 1, with a number of 16 pairs of 32.

[0048] The preparation process of the unidirectional grid structure reinforced foam sandwich composite material described in Example 1 is as follows:

[0049] 1) Forward laying and fixing of foam blocks 1. According to the structural design, the foam blocks 1 are laid forward and spaced on the mold in sequence, and fixed with positioning blocks / limiting blocks. The spacing between adjacent foam blocks 1 is the same and they are parallel to each other.

[0050] 2) Laying the first dry fiber cloth 3. Lay the cut first dry fiber cloth 3 evenly on the neatly laid foam blocks 1 at regular intervals in the positive direction.

[0051] 3) Reverse laying of foam blocks 1: Reverse laying of foam blocks 1 on the first dry fiber cloth 3 between adjacent forward-laid foam blocks 1, and squeezing the foam blocks 1 from top to bottom into the gaps between adjacent forward-laid foam blocks 1.

[0052] 4) Preparation of unidirectional grid structure reinforced foam board 4. After the unidirectional grid structure reinforced foam board preform is prepared, the unidirectional grid structure reinforced foam board 4 is prepared by VARI molding process, and the first dry fiber cloth 3 is molded into a unidirectional grid structure 5.

[0053] 5) Surface treatment of the one-way grid structure reinforced foam board 4. The surface of the one-way grid structure reinforced foam board 4 is polished with 320-grit sandpaper, then wiped clean with alcohol or acetone and dried.

[0054] 6) Laying of the lower panel 11. The number of layers of fiber fabric to be laid is determined according to the target thickness of the lower panel 11 and the selected fiber fabric type; the size of the cut fiber fabric is determined according to the plane size of the unidirectional grid structure reinforced foam board 4, and the fiber fabric size is 20 mm larger than the plane size of the unidirectional grid structure reinforced foam board 4, and then the fiber fabric is laid on the mold according to the layer design.

[0055] 7) Laying of the one-way grid structure reinforced foam board 4. Lay the one-way grid structure reinforced foam board 4 on the lower panel 11.

[0056] 8) Laying of the upper panel 13. Determine the number of layers of fiber fabric to be laid according to the target thickness of the upper panel 13 and the selected fiber fabric type; the size of the cut fiber fabric is the same as that of the fiber fabric for the lower panel 11, and then lay the fiber fabric on the unidirectional grid structure reinforced foam board 4 according to the layer design.

[0057] 9) Integral molding: After the above-mentioned unidirectional grid structure reinforced foam sandwich composite material preform is prepared, it is integrally molded by using a VARI molding process.

[0058] Embodiment 2

[0059] Embodiment 2 involves the type and density of foam core material, structural parameters and quantity of foam block 1, number of layers of dry fiber cloth 3 for unidirectional grid structure 5, molding process of unidirectional grid structure reinforced foam board 4, type and number of layers of dry fiber cloth for lower panel 11 and upper panel 13, etc., which are the same as those of Embodiment 1. The difference is that the type of dry fiber cloth 3 for unidirectional grid structure 5 is satin high-strength glass fiber fabric with a surface density of 220 g / m2.

[0060] The preparation process and molding process of the unidirectional grid structure reinforced foam sandwich composite material described in Example 2 are the same as those in Example 1.

[0061] Embodiment 3

[0062] Embodiment 3 involves the same structural parameters and quantity of the foam block 1, the number of layers of dry fiber cloth 3 used in the unidirectional grid structure 5, the molding process of the unidirectional grid structure reinforced foam board 4, the type and number of layers of dry fiber cloth used in the lower panel 11 and the upper panel 13 as in Embodiment 1, except that the foam core material type is 110kg / m3 PMI foam.

[0063] The preparation process and molding process of the unidirectional grid structure reinforced foam sandwich composite material described in Example 3 are the same as those in Example 1.

[0064] Embodiment 4

[0065] Embodiment 4 involves the type and density of foam core material, the number of foam blocks 1, the type and number of layers of dry fiber cloth 3 for the one-way grid structure 5, the molding process of the one-way grid structure reinforced foam board 4, the type and number of layers of dry fiber cloth for the lower panel 11 and the upper panel 13, etc., which are the same as those of Embodiment 1. The difference lies in the structural parameters and number of foam blocks 1.

[0066] The cross section of the foam block 1 is an isosceles trapezoid, with an upper base of 20 mm, a lower base of 43.5 mm, a height of 20 mm, and a quantity of 25. Therefore, the one-way grid structure reinforced foam board 4 is 1200 mm long, 810 mm wide, and 20 mm high. Correspondingly, the cross section of the positioning block / limiting block is the same as that of the foam block 1, and the quantity is 13 pairs of 26.

[0067] The preparation process and molding process of the unidirectional grid structure reinforced foam sandwich composite material described in Example 4 are the same as those in Example 1.

[0068] Embodiment 5

[0069] like Figures 6 to 8 As shown, Example 5 is a preparation method for a bidirectional grid structure reinforced foam sandwich composite material

[0070] The foam core material is 60kg / m3 PVC foam; the foam block 1 is 950mm long, 40mm wide, and 20mm high, with a number of 31, and the spacing between adjacent foam blocks 1 is 40.4mm; the dry fiber cloth 3 used in the unidirectional grid structure 5 is a twill carbon fiber fabric with a surface density of 198g / m2, with a number of 1 layer; the dry fiber cloth used in the lower panel 11 and the upper panel 13 is an E glass fiber lattice cloth with a surface density of 400g / m2, with a number of 8 layers. Therefore, the unidirectional grid structure reinforced foam board 4 is 1246mm long, 950mm wide, and 20mm high. In addition, the cross section of the positioning block / limiting block is the same as that of the foam block 1, with a number of 16 pairs of 32.

[0071] Processing the one-way grid structure reinforced foam board 4 can obtain the one-way grid structure reinforced foam block 6, which has the dimensions of 1200 mm in length, 40.4 mm in width, 20 mm in height, and 21 in number. It can be seen that the two-way grid structure reinforced foam board 9 has the dimensions of 1200 mm in length, 844 mm in width, and 20 mm in height. Accordingly, the cross section of the positioning block / limiting block is the same as that of the one-way grid structure reinforced foam block 6, and the number is 11 pairs of 22.

[0072] 1) Forward laying and fixing of foam blocks 1. According to the structural design, the foam blocks 1 are laid forward and spaced on the mold in sequence, and fixed with positioning blocks / limiting blocks. The spacing between adjacent foam blocks 1 is the same and they are parallel to each other.

[0073] 2) Laying the dry fiber cloth 3. Lay the cut dry fiber cloth 3 evenly on the neatly laid foam blocks 1 at regular intervals in the positive direction.

[0074] 3) Reverse laying of foam blocks 1: Reverse laying of foam blocks 1 on the dry fiber cloth 3 between adjacent forward-laid foam blocks 1, and squeezing them from top to bottom into the gaps between adjacent forward-laid foam blocks 1.

[0075] 4) Preparation of unidirectional grid structure reinforced foam board 4. After the unidirectional grid structure reinforced foam board preform is prepared, the unidirectional grid structure reinforced foam board 4 is prepared by RTM molding process, and the dry fiber cloth 3 is formed into a unidirectional grid structure 5.

[0076] 5) Surface treatment of the one-way grid structure reinforced foam board 4. The surface of the one-way grid structure reinforced foam board 4 is polished with 320-grit sandpaper, then wiped clean with alcohol or acetone and dried.

[0077] 6) Processing of the one-way grid structure reinforced foam board 4. The prepared one-way grid structure reinforced foam board 4 is processed according to the structural design, that is, the one-way grid structure reinforced foam board 4 is cut perpendicular to the grid structure direction, thereby obtaining a strip-shaped one-way grid structure reinforced foam block 6.

[0078] 7) Forward laying and fixing of the unidirectional grid structure reinforced foam blocks 6. According to the structural design, the unidirectional grid structure reinforced foam blocks 6 are laid forward and spaced on the mold in sequence, and fixed with positioning blocks / limiting blocks. The spacing between adjacent unidirectional grid structure reinforced foam blocks 6 is the same and they are parallel to each other.

[0079] 8) Laying the dry fiber cloth 8. Lay the cut dry fiber cloth 8 evenly on the neatly laid unidirectional grid structure reinforced foam blocks 6 at regular intervals in the positive direction.

[0080] 9) Reverse laying of unidirectional grid structure reinforced foam blocks 6. On the dry fiber cloth 8, unidirectional grid structure reinforced foam blocks 6 are reversely laid between adjacent forward-laid unidirectional grid structure reinforced foam blocks 6, and squeezed from top to bottom into the gaps between adjacent forward-laid unidirectional grid structure reinforced foam blocks 6.

[0081] 10) Preparation of bidirectional grid structure reinforced foam board 9. After the bidirectional grid structure reinforced foam board preform is prepared, the bidirectional grid structure reinforced foam board 9 is prepared by RTM molding process, and the dry fiber cloth 8 is molded into a bidirectional grid structure 10.

[0082] 11) Surface treatment of the bidirectional grid structure reinforced foam board 9. The surface of the bidirectional grid structure reinforced foam board 9 is polished with 320-grit sandpaper, then wiped clean with alcohol or acetone and dried.

[0083] 12) Laying the lower panel 11. Determine the number of fiber fabric layers to be laid according to the target thickness of the lower panel 11 and the selected fiber fabric type; determine the size of the cut fiber fabric according to the plane size of the bidirectional grid structure reinforced foam board 9, which is 20 mm larger than the plane size of the bidirectional grid structure reinforced foam board 9, and then lay the fiber fabric on the mold according to the layer design.

[0084] 13) Laying the bidirectional grid structure reinforced foam board 9. Lay the bidirectional grid structure reinforced foam board 9 on the lower panel 11.

[0085] 14) Laying of the upper panel 13. Determine the number of layers of fiber fabric to be laid according to the target thickness of the upper panel 13 and the selected fiber fabric type; the size of the cut fiber fabric is the same as that of the fiber fabric for the lower panel 11, and then lay the fiber fabric on the bidirectional grid structure reinforced foam board 9 according to the laying design.

[0086] 15) Integral molding: After the grid structure reinforced foam sandwich composite material preform is prepared, it is integrally molded by RTM molding process.

[0087] Embodiment 6

[0088] Example 6 involves the type and density of foam core material, structural parameters and quantity of foam block 1, structural parameters and quantity of unidirectional grid structure reinforced foam block 6, type and number of layers of dry fiber cloth 3 for unidirectional grid structure 5, type of dry fiber cloth 8 for bidirectional grid structure 10, type and number of layers of dry fiber cloth for lower panel 11 and upper panel 13, etc., which are the same as Example 5, except that the number of layers of dry fiber cloth used in unidirectional grid structure 10 is 2.

[0089] The preparation process and molding technology of the bidirectional grid structure reinforced foam sandwich composite material described in Example 6 are the same as those in Example 5.

[0090] Embodiment 7

[0091] Example 7 involves the type and density of foam core materials, structural parameters and quantity of foam blocks 1, structural parameters and quantity of unidirectional grid structure reinforced foam blocks 6, types and number of layers of dry fiber cloth 3 for unidirectional grid structure 5 and dry fiber cloth 8 for unidirectional grid structure 10, types and number of layers of fiber cloth for upper panel 13, number of layers of fiber cloth for lower panel 11, etc., which are the same as those of Example 5. The difference is that the type of fiber cloth for lower panel 11 is T700 carbon fiber biaxial fabric with a surface density of 400g / m2.

[0092] The preparation process and molding technology of the bidirectional grid structure reinforced foam sandwich composite material described in Example 7 are the same as those in Example 5.

[0093] Embodiment 8

[0094] Embodiment 8 is the same as Embodiment 5 in terms of the type and density of foam core material, structural parameters and quantity of foam block 1, structural parameters and quantity of unidirectional grid structure reinforced foam block 6, types and number of layers of dry fiber cloth 3 for unidirectional grid structure 5 and dry fiber cloth 8 for bidirectional grid structure 10, types and number of layers of fiber cloth for upper panel 13, types of fiber cloth for lower panel 11, etc., except that the number of types of fiber cloth for lower panel 11 is 5 layers.

[0095] The preparation process and molding technology of the bidirectional grid structure reinforced foam sandwich composite material described in Example 8 are the same as those in Example 5.

[0096] Embodiment 9

[0097] Embodiment 9 is the same as Embodiment 5 in terms of the type and density of the foam core material, the structural parameters and quantity of the foam block 1, the type and number of layers of the dry fiber cloth 3 for the unidirectional grid structure 5 and the dry fiber cloth 8 for the bidirectional grid structure 10, the type and number of layers of the fiber cloth for the lower panel 11 and the upper panel 13, etc. The difference lies in the structural parameters and quantity of the unidirectional grid structure reinforced foam block 6.

[0098] As in Example 5, the one-way grid structure reinforced foam board 4 is 1246 mm long, 950 mm wide, and 20 mm high. The one-way grid structure reinforced foam board 4 is processed to obtain a one-way grid structure reinforced foam block 6, which is 1200 mm long and has an isosceles trapezoidal cross section. The upper base of the isosceles trapezoid is 20 mm, the lower base is 43.5 mm, and the height is 20 mm. The number is 25. Thus, a two-way grid structure reinforced foam board 9 can be obtained, and the size is 1200 mm long, 810 mm wide, and 20 mm high. Correspondingly, the cross section of the positioning block / limiting block is the same as that of the one-way grid structure reinforced foam block 6, and the number is 13 pairs of 26.

[0099] The preparation process and molding technology of the bidirectional grid structure reinforced foam sandwich composite material described in Example 9 are the same as those in Example 5.

[0100] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for preparing a sandwich structure composite material based on grid-reinforced foam, characterized in that: The specific steps include: (1) Place the foam blocks on the mold in a positive direction in accordance with the structural design and fix them with positioning blocks / limiting blocks. The spacing between adjacent foam blocks should be the same and they should be parallel to each other. (2) Lay the cut first dry fiber cloth evenly on the neatly spaced foam blocks laid in the forward direction; (3) placing a foam block in the reverse direction on the first dry fiber cloth and between adjacent foam blocks placed in the forward direction, and squeezing the foam block into the gap between adjacent foam blocks placed in the forward direction from top to bottom; (4) After the unidirectional grid structure reinforced foam board preform is prepared, the unidirectional grid structure reinforced foam board is prepared by LCM molding process, and the unidirectional grid structure is obtained after the first dry fiber cloth is formed; (5) The surface of the one-way grid structure reinforced foam board is polished with 200-400 mesh sandpaper, then wiped clean with alcohol or acetone and dried; (6) processing the prepared unidirectional grid structure reinforced foam board according to the structural design, that is, cutting the unidirectional grid structure reinforced foam board perpendicular to the grid structure direction, thereby obtaining a strip-shaped unidirectional grid structure reinforced foam block; (7) According to the structural design, the unidirectional grid structure reinforced foam blocks are laid out in the mold in a positive direction and fixed with positioning blocks / limiting blocks. The spacing between adjacent unidirectional grid structure reinforced foam blocks is the same and they are parallel to each other; (8) Laying the cut second dry fiber cloth evenly on the neatly laid unidirectional grid structure reinforced foam blocks at regular intervals in the positive direction; (9) placing a unidirectional grid structure reinforced foam block in the reverse direction on the second dry fiber cloth and between adjacent unidirectional grid structure reinforced foam blocks placed in the forward direction, and squeezing the unidirectional grid structure reinforced foam block into the gap between adjacent unidirectional grid structure reinforced foam blocks placed in the forward direction from top to bottom; (10) After the bidirectional grid structure reinforced foam board preform is prepared, the bidirectional grid structure reinforced foam board is prepared by LCM molding process, and the bidirectional grid structure is obtained after the second dry fiber cloth is formed; (11) The surface of the bidirectional grid structure reinforced foam board is polished with 200-400 mesh sandpaper, then wiped clean with alcohol or acetone and dried; (12) Determine the number of fiber fabric layers to be laid according to the target thickness of the lower panel and the selected fiber fabric type; determine the size of the cut fiber fabric according to the plane size of the grid-reinforced foam, i.e., the unidirectional grid structure reinforced foam board or the bidirectional grid structure reinforced foam board. The fiber fabric size is 5 mm to 100 mm larger than the plane size of the grid-reinforced foam. Then, lay the fiber fabric on the mold according to the layer design; (13) Lay grid-reinforced foam on the lower panel; (14) Determine the number of fiber fabric layers required based on the target thickness of the upper panel and the selected fiber fabric type; cut the fiber fabric to the same size as the fiber fabric for the lower panel, and then lay the fiber fabric on the grid reinforcement foam according to the layer design; (15) The preform is integrally formed by LCM molding process.

2. The preparation method according to claim 1, characterized in that: The foam block is at least one of polyvinyl chloride (PVC), polymethacrylimide (PMI), polyethylene terephthalate (PET), polyurethane (PU), and polyimide (PI). The foam block has a density of ≤400kg / m3 and a length of 200mm-4000mm.

3. The preparation method according to claim 1, characterized in that: The cross-sectional dimension tolerance of the foam blocks is within ±0.5 mm, and the spacing tolerance between adjacent foam blocks is within ±0.5 mm.

4. The preparation method according to claim 1, characterized in that: The number of the foam blocks is ≥2N+1, 1≤N≤100 and N is an integer.

5. The preparation method according to claim 1, characterized in that: The first dry fiber cloth and the second dry fiber cloth are at least one of glass fiber, carbon fiber, carbon / glass hybrid fiber, quartz fiber, Kevlar fiber, ultra-high molecular weight polyethylene fiber, and PBO fiber; the material selection of the first dry fiber cloth and the second dry fiber cloth is independent of each other.

6. The preparation method according to claim 1, characterized in that: The length of the unidirectional grid structure reinforced foam block is 200mm-4000mm.

7. The preparation method according to claim 1, characterized in that: The thickness of the one-way grid structure reinforced foam block is 0-10mm greater than the thickness of the one-way grid structure reinforced foam board.

8. The preparation method according to claim 1, characterized in that: The reinforcing fibers for the lower panel and the upper panel are at least one of glass fiber, carbon fiber, carbon / glass hybrid fiber, quartz fiber, Kevlar fiber, ultra-high molecular weight polyethylene fiber, and PBO fiber; the material selection of the fiber fabrics for the lower panel and the upper panel is independent of each other.

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