A three-dimensional reinforced sandwich composite material and its preparation method

Abstract

This invention discloses a method for preparing a three-dimensional reinforced sandwich composite material, comprising the following steps: S1, creating cross-shaped grooves on two corresponding sides of a cubic foam to obtain a foam sandwich structure; S2, sequentially winding fibers circumferentially along the Y, Z, and X axes of the cross-shaped grooves, perpendicular to the center of the plane containing the cross-shaped grooves; S3, filling the cross-shaped grooves with a cross-shaped foam filling layer; S4, attaching prepreg to the prisms of the H-shaped surface of the foam sandwich structure; S5, repeating steps S1-S4 until the cross-shaped grooves are filled to a plane, followed by heating and pressurizing for curing to obtain the three-dimensional reinforced sandwich composite material. The sandwich composite material board prepared by this invention can fully utilize the strength of carbon fibers, with a weight 1.71 times that of foam materials of the same volume, and longitudinal and transverse moduli both 37.64 times that of foam materials; furthermore, it reduces weight by 54.4% compared to CFRP, and its transverse modulus is 2.74 times that of CFRP.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding technology, specifically relating to a method for preparing three-dimensional reinforced sandwich composite materials by circumferential fiber winding and its molding process. Background Technology

[0002] Three-dimensional weaving can reinforce in three directions, but the weaving process is complex and the cost is high. Although laying fiber cloth on three sides can also achieve the effect of three-dimensional reinforcement, the fibers are not continuous and the strength is affected. At the same time, the fiber cloth also needs to be 2D woven, which will also increase the cost.

[0003] The winding process is divided into three main categories: circumferential winding, longitudinal winding, and spiral winding. Among them, spiral winding has a complex line shape and operating system, requiring specific program operation to complete, which greatly increases the cost of winding machines that can achieve spiral winding. Longitudinal winding is only suitable for molding products of specific shapes (such as spheres), with a narrow application range, and the cost of winding machines is also high.

[0004] Existing triaxial reinforced composite materials mostly use three-dimensional braided fibers as the reinforcing phase. However, three-dimensional braiding requires the preparation of expensive and complex three-dimensional braiding machines. At the same time, the three-dimensional braiding process causes significant wear on the fibers, resulting in a strength loss of more than 30%, which prevents them from achieving their higher strength. Summary of the Invention

[0005] The purpose of this invention is to provide a molding method for three-dimensional reinforced sandwich composite materials. It adopts a simple circumferential fiber winding process to achieve reinforcement in three directions, reducing the processing difficulty and cost of traditional three-dimensional reinforced fabrics, while obtaining ideal mechanical properties.

[0006] To achieve the above objectives, the present invention provides a method for preparing a three-dimensional reinforced sandwich composite material, comprising the following steps:

[0007] S1. A cross-shaped groove is made on the first and second surfaces of the cube-shaped foam, with the second surface located on the back of the first surface, to obtain a foam sandwich structure;

[0008] S2. Using the center lines of the two grooves perpendicular to the cross-shaped groove as the Y-axis and Z-axis respectively, first use the Y-axis as the winding axis to wind fibers circumferentially within the cross-shaped groove of the foam sandwich structure, then change the Z-axis as the winding axis to wind fibers circumferentially within the cross-shaped groove of the foam sandwich structure; using the vertical line of the center of the platform where the bottom of the cross-shaped groove is located as the X-axis, and using the X-axis as the winding axis, wind fibers around the outer periphery of the side of the platform.

[0009] S3. Fill the cross-shaped groove with a cross-shaped foam filling layer;

[0010] S4. Apply prepreg along the length of the H-shaped prism formed by the groove wall of the cross-shaped groove of the foam sandwich structure;

[0011] S5. Repeat steps S1-S4 until the cross-shaped groove is filled into a plane, and then heat and pressurize to solidify and form a three-dimensional reinforced sandwich composite material.

[0012] Preferably, the fiber in step S2 is a resin-impregnated fiber.

[0013] Preferably, in step S3, a square groove of the same width as the cross shape and a depth of one fiber layer thickness is provided at the center intersection of one cross-shaped surface of the cross-shaped foam filling layer; during filling, the side of the cross-shaped foam filling layer with the square groove faces inward.

[0014] Preferably, the prepreg in step S4 is a carbon fiber reinforced epoxy resin-based prepreg with a single layer in the middle and double layers at both ends.

[0015] Preferably, in step S4, when the prepreg is laid, the single layer is located on the platform, and the double layer is symmetrically attached to the corresponding prisms on both sides of the platform.

[0016] Preferably, the curing conditions in step S5 are 25-200℃ and 0.1-0.3MPa.

[0017] This invention provides a three-dimensional reinforced sandwich composite material, comprising a foam sandwich structure, wherein a first surface and a second surface of the foam sandwich structure are provided with cross-shaped grooves, and the second surface is located on the back side of the first surface; the cross-shaped grooves are filled by alternately laying wound fibers and filling cross-shaped foam filling layers until the grooves are filled, and prepreg is attached along the length direction of the H-shaped prism formed by the groove wall of the cross-shaped groove of the foam sandwich structure; and then the three-dimensional reinforced sandwich composite material is obtained by curing.

[0018] Preferably, the fiber is a resin-impregnated fiber, and the prepreg is a carbon fiber reinforced epoxy resin-based prepreg with a single layer in the middle and double layers at both ends; the single layer is attached to the platform, and the double layers are symmetrically attached to the corresponding prisms on both sides of the platform.

[0019] Preferably, the bottom of the cross-shaped groove is surrounded by fiber on the outer periphery of the platform side.

[0020] Preferably, a square groove of the same width as the cross shape and a depth of one fiber layer thickness is provided at the center intersection of one cross-shaped surface of the cross-shaped foam filling layer; when filling, the side of the cross-shaped foam filling layer with the square groove faces inward.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The continuous fiber, triaxially reinforced sandwich composite material plate prepared by this invention can fully utilize the strength of carbon fiber, and the molding process is simple and low in cost. The weight of the same volume is 1.71 times that of foam material, while the longitudinal modulus and transverse modulus are both 37.64 times that of foam material; and it is 54.4% lighter than CFRP, and the transverse modulus is 2.74 times that of CFRP. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the side structure of the foam sandwich of the present invention;

[0024] Figure 2 This is a schematic diagram of the front structure of the foam sandwich of the present invention;

[0025] Figure 3 This is a schematic diagram of the structure of the foam filling layer, a novel structural material of this invention;

[0026] Figure 4 This is a schematic diagram of the prepreg plane of the novel structural material of this invention;

[0027] Figure 5 This is a right view of the novel structural material foam sandwich structure of the present invention;

[0028] Figure 6 This is a front view of the novel structural material foam sandwich structure of this invention;

[0029] Figure 7 This is a top view of the novel structural material foam sandwich structure of this invention;

[0030] Figure 8 This is a schematic diagram of the prepreg and foam sandwich composite structure of the novel structural material of this invention;

[0031] Figure 9 This is a schematic diagram of the six-way interface of the present invention;

[0032] Figure 10 This is a statistical chart comparing the transverse and longitudinal moduli of the material prepared in this invention with those of foam and CFRP;

[0033] Figure 11 This is a schematic diagram of the finished product obtained by curing and molding the new structural material prepared according to the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but this does not limit the present invention in any way.

[0035] Unless otherwise specified, the instruments, reagents, and materials used in the following embodiments are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods used in the following embodiments are all conventional experimental methods and detection methods already available in the prior art.

[0036] As attached Figure 1-2 As shown, this is the foam core of the novel structural material of the present invention, as illustrated in the attached diagram. Figure 3 The image shows a foam filling layer. The foam core has cross-shaped grooves on both sides. The foam filling layer is a cross-shaped foam board with a single-layer thickness of t and a cross-sectional side length of l. Y , l Z .

[0037] As attached Figure 4 As shown, the lengths of the single-layer prepreg in the Y and Z directions are y and z, respectively. The prepreg is laid on the two corners of the "H"-shaped surface of the foam core. The length of the single-layer portion in the middle of the prepreg is l+2(N-1)(t+d), and the total length of the double-layer portion is L-(l+2(N-1)(t+d)). The prepreg is a carbon fiber reinforced epoxy resin-based prepreg, or a prepreg of other fibers and resins.

[0038] As attached Figure 5-7 As shown, the long side of the "H"-shaped surface of the foam core is L, and the short side lengths are z and y respectively. After the winding / sanding is completed, the dimensions of the three sides of the product are L, M, and K respectively.

[0039] Based on the required dimensions of the new structure, an N-layer winding is designed. When winding around the X-axis, the width of each layer is Cx = l + 2(N-1)(t+d), and when winding around the Y-axis, the width of each layer is C. Y =l Y When winding around the Z-axis, the width of each winding layer is C. Z =l Z Prepare N pieces of prepreg, each with a width of Q. Y+Z =y+z, single layer in the middle, double layers on both sides, the length of the single layer in the middle of each prepreg is Q. X1 = l + 2(N-1)(t + d), with the length of the double-layered section on both sides being Q. X2 =L-(l+2(N-1)(t+d)), when preparing the prepreg, first cut a piece of length Q. X1 +2Q X2 Width is Q Y+Z The single-layer prepreg is then cut into two pieces of length Q. X2 Width is Q Y+Z A single layer of prepreg is laid and attached to both ends of the first prepreg; N cross-shaped foam filler layers with a thickness of t are prepared, with a recessed depth of d in the middle rectangular area, and a width and single-sided length of l in the Y direction.Y And y+2Nd, the width and single-sided length in the Z direction are l respectively. Z The dimensional relationships of the winding layer, prepreg layer, and foam layer, and z+2Nd, are shown in Table 1:

[0040] Table 1. Dimensional Relationship of Wrapping Layer, Prepreg Layer, and Foam Layer

[0041]

[0042]

[0043] The specific method includes the following steps:

[0044] 0. As attached Figure 9 As shown, a foam sandwich structure is used as the mold, and a six-way interface is embedded in the center of the mold for screwing in six winding shafts in three directions;

[0045] 1. First, using the Y-axis as the winding axis, wind one layer circumferentially within the "+" groove of the foam sandwich structure. Y Resin-impregnated fibers of varying widths;

[0046] 2. Replace the Z-axis with the winding axis, and wind one layer circumferentially within the "+" groove of the foam sandwich structure. Z Resin-impregnated fibers of varying widths;

[0047] 3. Change X to the winding axis, at the middle position in the X direction (e.g.) Figure 8 (The area marked with dashed lines) is wrapped with one layer of resin-impregnated fibers, each layer being l wide.

[0048] 4. At this point, the six centers of the foam sandwich structure have been wrapped with two orthogonal layers of fiber with a thickness of 2d, while the other wrapped positions have one layer of fiber with a thickness of d.

[0049] 5. Place a layer of cross-shaped foam filling material into each of the cross-shaped grooves in the foam sandwich structure, as shown in the attached diagram. Figure 9 As shown, the foam filling layer has a concave surface in the middle that is close to the winding layer;

[0050] 6. The four cross sections of the "+" shaped foam filling layer are all 2d higher than the "+" shaped groove of the foam sandwich structure, and are in a planar state with the central winding surface of the foam sandwich structure;

[0051] 7. On all four edges of the "H"-shaped surface of the foam sandwich structure, apply a single layer of prepreg in the middle and double layers on both sides (e.g., Figure 8 (Striped section); a single layer is laid as a whole onto the middle platform of the foam sandwich structure, and double layers are respectively attached to the stacked prisms.

[0052] 8. Repeat steps 1-7 above N times;

[0053] 9. The "+" groove of the foam sandwich structure consists of 2N layers of winding layers and N layers of "+" foam filling layers;

[0054] 10. The “H” shaped surface of the foam sandwich structure consists of 2N layers of winding layers and N layers of prepreg;

[0055] 11. All six surfaces are planar, and several layers of composite material can be wrapped around the outer surface as needed;

[0056] 12. After winding, remove the six shafts. The fibers near the winding shafts merge into one under the action of winding tension. Then, heat and pressurize this three-dimensional sandwich material to solidify it into a block structure material.

[0057] The heating and pressurization are carried out in an autoclave, with the pressure ranging from 0.1 to 0.3 MPa, depending on the curing temperature of the resin (room temperature 25-200℃) and the temperature resistance of the foam.

[0058] Example 1

[0059] l = 10 mm, L y =10mm,L z =10mm,y=10mm,z=10mm,t=2mm,d=1mm,l z =10mm,l y =10mm, N=2, foam material density 0.4g / cm³ 3 The density of the composite material is 1.5 g / cm³. 3 .

[0060] Based on the dimensional relationships in Table 1, the following can be calculated:

[0061] L = l + N(t + d) = 16 mm

[0062] M = l z +2z=30mm

[0063] K = l y +2y=30mm

[0064] V 总 =L×M×K=14.4cm 3

[0065] Composite layer volume (including winding layer and prepreg layer): V1 = NMKd = 1.8cm 3 V2 = NLKd = 0.96cm 3 V3 = LMNd = 0.96cm 3 ,

[0066] V 复合材料 =V 1+V2 + V3 = 3.72cm 3

[0067] The volume of the foam material (including the foam sandwich structure and the foam filling layer) V 泡沫 =V 总 -V 复合材料 =10.68cm 3

[0068] Therefore, for the same volume, CFRP weighs 21.6g, foam material weighs 5.76g, and the new structural material of this invention weighs 9.85g. Tests show that CFRP has a longitudinal modulus of 100GPa and a transverse modulus of 9.6GPa, foam material has a longitudinal modulus of 0.7GPa and a transverse modulus of 0.7GPa, and the new structural material of this invention has a longitudinal modulus of 26.35GPa and a transverse modulus of 26.35GPa. It can be seen that the weight of the new structural material of this invention for the same volume is 1.71 times that of the foam material, while its longitudinal and transverse moduli are both 37.64 times that of the foam material; the new structural material is 54.4% lighter than CFRP, and its transverse modulus is 2.74 times that of CFRP.

[0069] As attached Figure 10 As shown in the horizontal and vertical modulus statistics of the present invention, it can be seen that although the vertical modulus of CFRP is high, its horizontal modulus is low, which is a typical anisotropic material. The new structure of the present invention has the same horizontal and vertical modulus, and has a lighter weight and higher modulus, which is a new structural form with promising applications.

[0070] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for preparing a three-dimensional reinforced sandwich composite material, characterized in that, The following steps are involved: S1. A cross-shaped groove is made on the first and second surfaces of the cube-shaped foam, with the second surface located on the back of the first surface, to obtain a foam sandwich structure; S2. Using the center lines of the two grooves perpendicular to the cross-shaped groove as the Y-axis and Z-axis respectively, first use the Y-axis as the winding axis to wind fibers circumferentially within the cross-shaped groove of the foam sandwich structure, then change the Z-axis as the winding axis to wind fibers circumferentially within the cross-shaped groove of the foam sandwich structure; using the vertical line of the center of the platform where the bottom of the cross-shaped groove is located as the X-axis, and using the X-axis as the winding axis, wind fibers around the outer periphery of the side of the platform. S3. Fill the cross-shaped groove with a cross-shaped foam filling layer; S4. Apply prepreg along the length of the H-shaped prism formed by the groove wall of the cross-shaped groove of the foam sandwich structure; S5. Repeat steps S1-S4 until the cross-shaped groove is filled into a plane, and then heat and pressurize to solidify and form a three-dimensional reinforced sandwich composite material. In step S3, a square groove of the same width as the cross shape and a depth of one fiber layer thickness is provided at the center intersection of one cross-shaped surface of the cross-shaped foam filling layer; during filling, the side of the cross-shaped foam filling layer with the square groove faces inward; The prepreg described in step S4 is a carbon fiber reinforced epoxy resin-based prepreg with a single layer in the middle and double layers at both ends.

2. The method for preparing the three-dimensional reinforced sandwich composite material according to claim 1, characterized in that, The fiber mentioned in step S2 is a resin-impregnated fiber.

3. The method for preparing the three-dimensional reinforced sandwich composite material according to claim 1, characterized in that, In step S4, when the prepreg is laid, the single layer is located on the platform, and the double layer is symmetrically attached to the corresponding prisms on both sides of the platform.

4. The method for preparing the three-dimensional reinforced sandwich composite material according to claim 1, characterized in that, The curing conditions described in step S5 are 25-200℃ and 0.1-0.3MPa.

5. A three-dimensional reinforced sandwich composite material prepared by any one of the preparation methods of claims 1-4, characterized in that, The product includes a foam sandwich structure, wherein the first and second surfaces of the foam sandwich structure are provided with cross-shaped grooves, and the second surface is located on the back side of the first surface; the cross-shaped grooves are filled by alternately laying wound fibers and filling cross-shaped foam filling layers until the grooves are filled, and prepreg is attached along the length direction of the H-shaped prism formed by the groove wall of the cross-shaped groove of the foam sandwich structure; and then the product is cured and molded to obtain a three-dimensional reinforced sandwich composite material.

6. The three-dimensional reinforced sandwich composite material according to claim 5, characterized in that, The fiber is a resin-impregnated fiber, and the prepreg is a carbon fiber reinforced epoxy resin-based prepreg with a single layer in the middle and double layers at both ends; the single layer is attached to the platform, and the double layers are symmetrically attached to the corresponding prisms on both sides of the platform.

7. The three-dimensional reinforced sandwich composite material according to claim 5, characterized in that, The bottom of the cross-shaped groove is surrounded by fiber on the outer periphery of the platform side.

8. The three-dimensional reinforced sandwich composite material according to claim 5, characterized in that, The center of one cross-shaped surface of the cross-shaped foam filling layer is provided with a square groove of the same width as the cross shape and a depth of 1 layer of fiber thickness; when filling, the side of the cross-shaped foam filling layer with the square groove faces inward.

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