A method for connecting layers of a composite material and a corresponding composite material

Abstract

The present invention relates to the technical field of composite material connection, and discloses a composite material interlayer connection method and a corresponding composite material. The composite material interlayer connection method includes three processes: making an inlay, making a bottom layer, and making a surface layer. The inlay includes a bottom layer insert and a surface layer insert. The bottom layer insert is embedded in the bottom layer, and the surface layer insert is embedded in the surface layer. The surface layer insert and the bottom layer insert are fixedly connected, and the inlay is used to realize the fixed connection between the surface layer and the bottom layer. The composite material produced by using the composite material interlayer connection method of the present invention has the characteristics of high connection strength, low process risk, designable connection strength, and low manufacturing cost.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material connection, and particularly relates to a method for connecting composite material layers and a corresponding composite material. Background Art

[0002] Composite multi-layer connection materials have many advantages such as enhancing structural strength and stiffness, optimizing material utilization rate, improving fatigue resistance, enhancing environmental resistance, flexible design, reducing weight, improving manufacturing accuracy, and multi-functional integration. As a result, the composite material multi-layer connection process has been widely applied in many fields such as aerospace, automotive manufacturing, and construction.

[0003] Currently, the main methods for connecting composite material layers include mechanical connection, bonding, Z-Pin connection, stitching connection, fusion welding, and hybrid connection. Mechanical connection such as bolt connection requires drilling holes on the surface of the composite material web, which destroys the structural integrity of the composite material and causes local stress concentration, reducing the connection efficiency; in special environments, metal connectors are prone to electrochemical corrosion, and corresponding anti-corrosion technical treatments need to be carried out on the connecting bolts. The bonding method often cannot effectively ensure the structural safety of composite material components under fatigue due to the bonding strength of the adhesive. The stitching connection has high requirements for the stitching material, equipment, process, etc. Fusion welding is a unique connection method for thermoplastic composite materials. Hybrid connection is the comprehensive use of multiple connection methods.

[0004] The Z-Pin connection technology draws on the method of discontinuous stitching in stitched composites, and directly embeds rigid short rods in the thickness direction of the prepreg or foam sandwich before curing. These short rods are called Z-Pins. The Z-Pin material can be metal (such as stainless steel, aluminum alloy, and titanium alloy, etc.) or non-metal (such as carbon fiber, glass fiber, and Kevlar, etc. fibers). Metal Z-Pins are commonly used in composite materials with high requirements for interlaminar shear performance, while non-metal Z-Pins are mainly used for the conventional toughening of materials.

[0005] The Z-Pin connection technology for composite material layers is of great significance in fields such as aerospace, automotive, shipbuilding, construction, and sports equipment that require high-strength and lightweight materials, providing a new and effective solution for the connection of composite materials. With the wide application of composite materials in various fields, the performance requirements for composite materials are also getting higher and higher. As an effective interlaminar reinforcement method, the Z-Pin technology has broad development prospects. However, in practical applications, the Z-Pin technology also faces some challenges, such as how to further improve the bonding strength between the Z-Pin and the composite material matrix, etc.

[0006] At present, the connection between the surface layer and the web of composite materials is generally through bolt connection. In this structure, the web is a metal frame structure, and the fixation of bolts is achieved by drilling and tapping on the surface of the metal frame structure. However, with the improvement of the application technology of composite materials and the urgent need for weight reduction of composite materials, the web is gradually transformed from a metal structure to a composite material structure. After the composite material frame web is formed, the core material is filled and processed to complete the production of the composite material bottom layer, and then the surface layer is formed on the surface of the bottom layer. In this structure, the connection between the composite material frame web and the surface layer is only through resin bonding, and the low connection strength easily leads to delamination and debonding between the composite material surface layer and the web, resulting in connection failure.

[0007] Chinese Patent CN111452395A discloses a curved composite material connection structure, forming method and rail vehicle. In this invention, a plurality of thickening sheets are arranged on the bonding surface of the composite material curved skin, and these thickening sheets are made to contact the outer surface of the connecting beam, and at the same time, an adhesive layer is filled between the two, thereby improving the firmness and sealing performance of the bonding and reducing the processing difficulty. This invention belongs to the composite material connection of the bonding method. Although it does not damage the structural integrity of the composite material, it is restricted by the bonding strength of the adhesive and cannot effectively guarantee the structural safety of the composite material component under fatigue action.

[0008] Chinese Patent CN104847595A discloses a Z-pin reinforced composite material wind turbine blade structure and its manufacturing method. This structure implants Z-pins at the joint of the main beam and the upper and lower blade shells to improve the connection strength and anti-fatigue performance. This invention solves the problem of low joint surface strength in the traditional bonding method, and significantly improves the overall performance of the wind turbine blade. However, this invention is a specific process and method for the manufacture of wind turbine blades, and uses a nail gun to shoot Z-Pins into points at high speed, which is more suitable for curved surface structures. The present invention is applicable to various composite material plate structures, and there are obvious differences from it in aspects such as the preparation of Z-Pins, the combination with the composite material matrix, and the process flow. Summary of the Invention

[0009] In view of this, the present invention aims to propose a composite material interlayer connection method and the corresponding composite material to further improve the bonding strength between the inlay and the composite material matrix, with the advantages of high connection reliability, low process risk, designable connection strength, free control of the inlay spacing, and low manufacturing cost.

[0010] To achieve the above object, the technical solution of the present invention is realized as follows:

[0011] A method for connecting layers of a composite material includes three processes: making an inlay, making a bottom layer, and making a surface layer. The inlay includes a bottom-layer insert and a surface-layer insert. The bottom-layer insert is embedded in the bottom layer, and the surface-layer insert is embedded in the surface layer. The surface-layer insert and the bottom-layer insert are fixedly connected, and the inlay is used to enhance the fixed connection between the surface layer and the bottom layer. Since the bottom-layer insert and the surface-layer insert are fixedly connected as a whole, the inlay actually forms a new Z-pin. This method innovates the Z-pin structure, significantly improving the overall load-bearing capacity and durability. At the same time, with a split design, it is possible to flexibly select a suitable inlay shape according to the materials and thicknesses of the surface layer and the bottom layer, providing convenience for actual production. Meanwhile, this also provides a variety of combinations of the bottom layer and the surface layer to meet various specific requirements.

[0012] Further, taking the surface of the bottom-layer insert extending in the length direction as the side surface, at least one of the side surfaces is recessed inward in the middle section. This setting provides a larger connection area and enhances the bonding strength with the matrix material.

[0013] Further, when making the inlay, the surface of the inlay is treated to improve the bonding strength. This includes: performing knurling, sandblasting, grooving, etc. on the surface to create regular raised or sunken patterns on the surface of the connecting piece, increasing the friction and contact area; performing geometric shape optimization such as threading and barbed design on the surface to further enhance the mechanical interlocking effect between the inlay and the matrix material.

[0014] Further, the treatment of the surface of the inlay is: a groove is opened in the bottom-layer insert perpendicular to the side surface. The shape of the groove can be various shapes, and a square groove is preferably selected considering the convenience of processing.

[0015] Further, the bottom layer includes a web, and the process of making the bottom layer includes: Step 1, connecting the bottom-layer insert to the web to form a web frame; Step 2, filling the web frame with a core material to form a core mold; Step 3, performing injection molding on the core mold to complete the production of the bottom layer. The built web frame is the main load-bearing component, and the core material plays a role in structural filling.

[0016] Further, the connection between the bottom-layer insert and the web can be achieved by integral molding or step-by-step molding. These are two schemes for connecting the bottom-layer insert and the web, and either one can be selected for use.

[0017] Further, the integral molding for connecting the web and the bottom-layer insert includes the following steps:

[0018] Step 1: Wind fiberglass yarn or prepreg in the direction perpendicular to the surface height of the bottom-layer insert. After filling the grooves on the surface of the bottom-layer insert, continue to wind fiberglass cloth or prepreg with different widths in the same direction on the surface of the bottom-layer insert until the depressions of the bottom-layer insert are filled;

[0019] Step 2: implant the bottom insert into the web preform;

[0020] Step 3: orthogonally lay the fiber fabric, lay the release fabric and the flow net in sequence, and complete the web forming through molding.

[0021] Through the integrated molding of the web and the bottom insert, the surface connection between the composite material and the bottom insert remains consistent in all directions. This design enables uniform stress distribution during loading, thus ensuring excellent connection strength.

[0022] Furthermore, the connection between the web and the bottom insert adopts step-by-step molding, including the following steps:

[0023] Step 1: roughen the fixing surface of the web and the bottom insert with sandpaper, and remove the dust on the surface of the web;

[0024] Step 2: sandblast the connection area between the bottom insert and the web, and bond and fix it with an adhesive;

[0025] Step 3: orthogonally lay the fiber fabric in the bonding area between the bottom insert and the web, with the bottom insert located between the fiber fabric and the web, then lay the release fabric and the flow net, and finally perform bag film sealing and vacuum-assisted molding to form the bottom insert-fixed composite material and complete the fixation of the bottom insert.

[0026] The step-by-step molding of the web and the bottom insert is another alternative for their connection, which can provide a suitable choice according to specific requirements.

[0027] Furthermore, the production of the surface layer includes the following steps:

[0028] Step 1: fixedly connect the surface insert and the bottom insert;

[0029] Step 2: lay the surface fiber fabric layer on the bottom surface;

[0030] Step 3: perform perfusion molding on the composite material surface layer to complete the connection between the composite material bottom layer and the surface layer.

[0031] Through the connection between the surface layer and the bottom layer, many advantages of multi-layer connection of composite materials can be realized.

[0032] Furthermore, when performing Step 2 to lay the surface fiber fabric layer on the bottom surface, the fiber fabric is perforated at the bottom insert, passes through the surface insert until the height of the fabric is the same as the upper surface of the surface insert; the subsequent laid fiber fabric is not perforated. This operation enables the close combination of the insert and the fiber fabric layer, achieving the effect of optimizing the internal stress distribution and improving the overall strength.

[0033] Furthermore, the opening pattern is a linear hole, and the opening directions of adjacent two layers of fabrics are perpendicular. Refining the opening direction enables the fabric to fit more closely with the inlay, improving the bonding strength between the inlay and the composite matrix.

[0034] Furthermore, a composite material is made by using the above-mentioned method for connecting composite material layers. The products produced by this method possess various advantages of multi-layer connection of composite materials and have prominent advantages in terms of structural strength and stiffness.

[0035] Compared with the prior art, the method for connecting composite material layers and the corresponding composite material according to the present invention have the following advantages:

[0036] 1. Significantly improve the interlayer strength: The present invention can significantly improve the interlayer fracture toughness and interlayer shear strength of the laminate, overcoming the shortcoming of the low interlayer shear strength of traditional bearing plates.

[0037] 2. Avoid stress concentration: The present invention does not damage the integrity of the composite material, can avoid the reduction of strength caused by stress concentration due to drilling in mechanical connection, reduce fatigue damage, and extend the service life.

[0038] 3. Improve reliability: Further improve the bonding strength between the inlay and the composite matrix, the inlay spacing can be freely controlled, and the connection reliability is high.

[0039] 4. Reduce costs: Select suitable materials according to the requirements of different layers to achieve the best configuration of materials. Compared with other methods, the cost is lower; at the same time, more precise manufacturing processes can be realized to ensure good bonding between layers and improve product quality.

[0040] 5. Wide application range: Different layers can integrate multiple functions, such as conductivity, heat insulation, sound absorption, etc.; the number of layers and material combinations can be flexibly adjusted according to specific application requirements, and the inlay spacing can also be freely controlled to meet diverse design requirements; the suitable inlay form can be flexibly selected according to the materials and thicknesses of the surface layer and the bottom layer, providing convenience for actual production.

[0041] 6. Strong environmental adaptability: Different material layers can provide different protection functions, and there are no problems such as electrochemical corrosion and moisture absorption in its products.

[0042] On the basis of not damaging the integrity of the composite material, the present invention optimizes the design of the inlay morphology, materials, etc., innovates the processing process steps, is an application innovation and practical expansion of the Z-Pin connection technology for composite material layers, and can be applied to the production of all-composite frame + surface structure products. Its products can be used for connecting the surface layer of large composite structures with the composite material skeleton, such as wind turbine blades, cruise ships, etc.

[0043] BRIEF DESCRIPTION OF THE DRAWINGS The drawings forming a part of this invention are used to provide a further understanding of the invention. The schematic embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. In the drawings:

[0044] Figure 1 is the connection diagram of the bottom layer and the surface layer according to Embodiment 1 of the present invention;

[0045] Figure 2 is the structural relationship diagram after the bottom layer insert is implanted into the web according to Embodiment 1 of the present invention;

[0046] Figure 3 is the structural relationship diagram after the bottom layer insert is implanted into the web according to Embodiment 2 of the present invention;

[0047] Figure 4 is the structural relationship diagram of the bottom layer after filling the core material according to Embodiment 2 of the present invention;

[0048] Figure 5 is the opening direction diagram of adjacent fabrics of the surface layer insert according to Embodiment 1 of the present invention;

[0049] Figure 6 The five views of the bottom layer insert according to Embodiment 2 of the present invention.

[0050] DESCRIPTION OF REFERENCE NUMERALS:

[0051] 1. Bottom layer insert; 2. Bottom layer insert fixing composite material; 3. Web; 4. Surface layer; 5. Surface layer insert; 6. Core material. DETAILED DESCRIPTION OF THE INVENTION

[0052] In order to make the technical means, objectives and effects of the present invention easy to understand, the embodiments of the present invention will be described in detail below with reference to specific drawings.

[0053] It should be noted that all the terms indicating directions and positions in the present invention, such as: "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", "top", "bottom", "lateral", "longitudinal", "center", etc., are only used to explain the relative positional relationship and connection situation between components in a certain specific state (as shown in the drawings), and are only for the convenience of describing the present invention, rather than requiring the present invention to be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention. In addition, the descriptions involving "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features.

[0054] In the description of the present invention, unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection; it may be a direct connection, or an indirect connection through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0056] Embodiment 1

[0057] A method for connecting composite material layers includes the following processes:

[0058] Process 1: Fabricate the inlay.

[0059] The inlay can be integral or split, and the material can be metal or non-metal.

[0060] The inlay of the present invention is columnar or rod-shaped, and the cross-sectional shape can be circular, polygonal, etc.; the inlay adopts a split design and is composed of a bottom inlay 1 and a surface inlay 5, and the surface inlay 5 is installed on the bottom inlay 1. Since the bottom inlay 1 and the surface inlay 5 are fixedly connected, the inlay actually forms a new Z-pin. This method innovates the Z-pin structure and significantly improves the overall load-bearing capacity and durability. At the same time, adopting a split design can flexibly select a suitable inlay form according to the materials and thicknesses of the surface layer 4 and the bottom layer, which provides convenience for actual production. In addition, this also provides a variety of combinations of the bottom layer and the surface layer 4 to meet various specific requirements.

[0061] The cross-sectional shape of the inlay affects the interfacial bonding strength between it and the composite material matrix. Good interfacial bonding is the key to ensuring that the inlay can effectively transfer loads and enhance the performance of the composite material. A circular or approximately circular cross-sectional shape may be more conducive to forming a uniform and dense interfacial bonding layer, thereby improving the bonding strength between the inlay and the composite material matrix. Compared with a circular cross-section, a polygonal cross-section can better bite with the matrix material, increasing the contact area and improving the anti-pull-out ability.

[0062] Preferably, the inlay material is metal; the surface inlay 5 is an M12 countersunk head bolt; asFigure 1 As shown, the size of the bottom insert 1 is 30mm×30mm×100mm (length×width×height), and the waist size is 20×20mm. Slots are cut in the direction perpendicular to the surface of the bottom insert 1, with a spacing of 30mm, and the cross-section of the slot is 2mm×2mm. The cross-section of the bottom insert 1 is square, and the side length is 3 times the diameter of the connecting bolt. The outer shape of the bottom insert 1 is machined.

[0063] Longer inserts can provide a larger connection area, thereby enhancing the connection strength between composite laminates. As the length increases, when subjected to external forces, the insert can better transfer the load to more matrix materials, reducing interfacial stress concentration. The setting of the bottom insert 1 with thicker ends and thinner middle is also to provide a larger connection area and enhance the bonding strength with the matrix material. The bottom insert 1 is selected with a square cross-section. On the one hand, it is for the convenience of insert processing; on the other hand, in the subsequent steps, fiberglass yarn prepreg is wound around its waist until the depression in the waist of the bottom insert 1 is filled, actually adjusting the interfacial bonding layer to be approximately circular, enhancing the connection strength.

[0064] The surface of the insert is treated to improve the connection strength, fixing effect, stress distribution, etc. It includes: performing knurling, sandblasting, slotting, etc. on the surface to create regular raised or sunken patterns on the surface of the connecting piece, increasing the friction and contact area; performing geometric shape optimization such as threads and barbed designs on the surface to further enhance the mechanical interlocking effect between the insert and the matrix material. The slot shape can be various shapes, and the preferred square slot is considered for the convenience of processing.

[0065] Process 2: Making the bottom layer. The bottom layer includes the web 3, including: First step, connecting the bottom insert 1 with the web 3 to form a web frame; Second step, filling the core material 6 in the web frame; Third step, core mold casting to complete the production of the bottom layer. The built web frame is the main load-bearing component, and the core material 6 plays a role in structural filling;

[0066] First step, connecting the bottom insert 1 with the web 3 to form a web frame:

[0067] The web 3 is a composite material. The connection between the bottom insert 1 and the web 3 is formed by integral molding or step-by-step molding. In Example 1, the connection between the web 3 and the bottom insert 1 is formed by integral molding, and in Example 2, the connection between the web 3 and the bottom insert 1 is formed by step-by-step molding.

[0068] Preferably, the integral molding of the bottom insert 1 and the web 3 includes the following steps:

[0069] Step 1: Treatment of the bottom insert 1. Wind fiberglass yarn with a width of 2 mm in the vertical height direction on the surface of the bottom insert 1. After filling the 2×2 mm grooves on the surface of the bottom insert 1, then continue to wind the surface of the bottom insert 1 with fiberglass cloth with a width of 5 mm in the same direction until the waist depression of the bottom insert 1 is filled. Winding with fiber fabrics or prepregs of different widths to fill the waist grooves and depressions of the bottom insert 1 is all for the purpose of increasing the connection strength between the composite material and the bottom insert 1.

[0070] Step 2: Insert the bottom insert 1 into the preform of the web 3. Insert the bottom insert 1 into the preform of the web 3, and the insertion structure is as Figure 2 shown. The preform of the web 3 is used to set the bottom insert 1 in a predetermined position and facilitate fixation.

[0071] Step 3: Orthogonally lay fiber fabrics, lay a release cloth and a flow net in sequence, and complete the forming of the web 3 through a forming process. The forming process includes at least one of vacuum-assisted forming, liquid forming, or resin transfer molding.

[0072] Preferably, lay 15 mm thick fiberglass fabric orthogonally on the mold surface, then put the bottom insert 1 wound with fiber fabric into the designated position, continue to lay 15 mm thick fiberglass fabric orthogonally, lay a release cloth and a flow net in sequence, and finally complete the forming of the web 3 through processes such as vacuum-assisted forming, liquid forming, or resin transfer molding.

[0073] Through integral forming, the surface connection between the composite material and the bottom insert 1 remains consistent in all directions. This setting makes the stress distribution uniform when the material is stressed, thus ensuring good connection strength.

[0074] The second step, fill the core material 6 into the web frame to form a core mold:

[0075] Provide support for the surface layer 4. According to the size of the web 3 frame, fill the core material 6 processed into a specific shape into the web frame, and the surface of the core material 6 is at the same height as the surface of the web 3. The specific shape refers to the contour shape matching the web frame, including but not limited to rectangle, rhombus, and irregular shape.

[0076] The third step, perform core mold infusion molding to complete the bottom layer production:

[0077] Use an adhesive to bond the core material 6 and the web 3, and then perform resin infusion into the bonding gap between the core material 6 and the web 3 through vacuum-assisted forming. Finally, machine process the surfaces of the web 3 and the core material 6 into a specified shape to complete the forming of the composite material bottom layer.

[0078] Process 3: Manufacture the surface layer 4.

[0079] Step 1: Fix the bottom insert 1 and the surface insert 5 in a connected manner. The length, shape, connection method, etc. of the surface insert 5 can be flexibly selected according to needs, taking into account performance and cost.

[0080] Preferably, drill holes on the upper surface of the bottom insert 1. The diameter of the drilled holes is smaller than the diameter of the bolts. Tap the bolt holes with a tap that matches the bolts, check whether there is interference between the bolts and the bolt holes, and clean the iron filings in the bolt holes. Uniformly apply thread glue on the stud surface of the bolts, implant the embedded bolts, and the embedded bolts protrude from the bottom insert 1 by a certain height. After the thread glue cures, check the fixing effect of the bolts to determine whether the bolts are firmly bonded and fixed. The height of the bolts is 2 / 3 of the thickness of the surface layer 4.

[0081] Preferably, the embedded bolts are M12 countersunk bolts, and the height protruding from the bottom insert 1 is 12 mm.

[0082] The combination of the bottom insert 1 + bolts is considered in view of the general availability of the surface insert 5, taking into account the economic cost. The height of the bolts can be flexibly adjusted according to the needs of the thickness of the surface layer 4.

[0083] Step 2: Lay the surface fiber fabric on the bottom surface. The fiber fabric is perforated at the bottom insert 1, passes through the surface insert 5 until the fabric is at the same height as the upper surface of the surface insert 5. After completing the perforation and laying of the fabric, trim the protruding fabric flat at the embedded bolts, and continue to lay the fiber fabric. The subsequent fiber fabric is not perforated. This operation enables the inlay to be closely combined with the fiber fabric layup, achieving the effect of optimizing the internal stress distribution and improving the overall strength.

[0084] Preferably, the shape of the opening is a slotted hole, and the opening directions of adjacent two layers of fabric are perpendicular. The bolts protrude through the slotted holes, as Figure 5 shown. Refining the opening direction enables the fabric to fit more closely with the inlay, improving the bonding strength between the inlay and the composite matrix.

[0085] Preferably, the thickness of the web 3 is 30 mm, and the material is a glass fiber reinforced vinyl resin composite material; the thickness of the surface layer 4 is 18 mm, and the material is a carbon fiber reinforced vinyl resin composite material. The two are orthogonally laid up.

[0086] Step 3: Inject and mold the composite material surface layer 4 to complete the connection between the composite material bottom layer and the surface layer 4. The composite material surface layer 4 is formed by liquid molding or hot pressing and injection molding. Lay the release cloth and the flow guiding net, and perform bag film sealing and resin injection to complete the connection between the composite material bottom layer and the surface layer 4.

[0087] The composite material multi-layer connection material fabricated by the method of the present invention has the following advantages: significantly improving the structural strength and stiffness of the composite material, thereby enhancing the overall performance; selecting appropriate materials according to the requirements of different layers to achieve the optimal configuration of materials, reducing waste and lowering costs; effectively dispersing stress concentration, reducing fatigue damage, and extending the service life; different material layers can provide different protective functions, such as anti-corrosion, anti-ultraviolet, etc., enhancing the environmental resistance performance; being able to flexibly adjust the number of layers and material combinations according to specific application requirements to meet diverse design requirements; on the premise of ensuring structural strength, through reasonable design of the multi-layer structure, the overall weight can be effectively reduced; being able to achieve more precise manufacturing processes, ensuring good bonding between layers, and improving product quality; different layers can integrate multiple functions, such as conductivity, heat insulation, sound absorption, etc., enabling a single structure to have multiple functions.

[0088] Example 2

[0089] A method for connecting composite material layers includes the following processes:

[0090] Process 1: Fabricate the inlay.

[0091] Preferably, the size of the bottom inlay 1 is 30mm×30mm×300mm (length×width×height). The four side surfaces along the height direction include three inwardly concave surfaces and one flat surface. The waist cross-section of the bottom inlay 1 is an isosceles trapezoid, as Figure 6 shown. There are square slots on the three inwardly concave surfaces, and the flat side surface is used for bonding with the web 3 surface.

[0092] Process 2: Fabricate the bottom layer. The bottom layer includes a web, including: First step, connect the bottom inlay 1 with the web 3 to form a web frame; Second step, fill the core material 6 in the web frame; Third step, perform core mold casting to complete the fabrication of the bottom layer. As Figure 4 shown.

[0093] Among them, the connection between the bottom inlay 1 and the web 3 is carried out by step-by-step forming. The step-by-step forming of the web 3 and the bottom inlay 1 includes the following steps:

[0094] Step 1: Surface treatment of the web 3. Use sandpaper to roughen the fixed surface of the web 3 and the bottom inlay 1, and use anhydrous ethanol to remove the dust on the surface of the web 3. Through the above treatment, the surface adhesion is improved and the bonding strength is enhanced.

[0095] Step 2: Bond and fix the bottom inlay 1 and the web 3. First, sandblast the connection area between the bottom inlay 1 and the web 3 to increase the surface roughness, then coat the vinyl adhesive on the flat side area of the bottom inlay 1, and coat the vinyl adhesive at the specified position on the web 3. Next, bond the adhesive-coated surface of the bottom inlay 1 with the adhesive-coated area of the web 3, extrude the excess adhesive, and use a scraper to scrape the extruded adhesive flat.

[0096] Step 3: Connect the bottom insert 1 and the web 3 to form a fabric. First, orthogonally lay the fiber fabric on the bonding area between the bottom insert 1 and the web 3. The laying thickness is preferably 5 mm. The length of the laid fiber fabric is preferably greater than 200 mm, and the width is the same as the height of the bottom insert 1. The center of the length direction is aligned with the center of the bottom insert 1. The bottom insert 1 is located between the fiber fabric and the web 3. Then lay the release fabric and the flow guide net. Finally, perform bag film sealing and vacuum-assisted forming to form the bottom insert-fixed composite material 2 and complete the fixation of the bottom insert 1. The implantation structure is as Figure 3 shown.

[0097] The step-by-step forming of the web 3 and the bottom insert 1 is an alternative for their connection and can provide a more suitable choice according to specific requirements.

[0098] Process 3: The same as Process 3 in Embodiment 1.

[0099] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for connecting between layers of a composite material, characterized in that, The method comprises three steps of making an inlay, making a bottom layer, and making a surface layer (4); the inlay comprises a bottom layer inlay (1) and a surface layer inlay (5); the bottom layer inlay (1) is embedded in the bottom layer, the surface layer inlay (5) is embedded in the surface layer (4), the surface layer inlay (5) and the bottom layer inlay (1) are fixedly connected, and the inlay is used to achieve a fixed connection between the enhanced surface layer (4) and the bottom layer; the making of the surface layer (4) comprises the following steps: Step 1: The surface insert (5) is fixedly connected to the bottom insert (1); Step 2: Laying the surface fiber fabric on the bottom surface; Step 3: The composite material surface layer (4) is injection molded to complete the connection between the composite material bottom layer and the surface layer (4).

2. The method for connecting composite material layers according to claim 1, wherein The surfaces of the bottom layer insert (1) extending in the length direction are taken as side surfaces, and at least one of the side surfaces is concave inwardly in the middle section.

3. The method for connecting composite material layers according to claim 1, characterized in that, When making the inlay, the surface of the inlay is treated to improve the bonding strength.

4. The method for connecting composite material layers according to claim 3, characterized in that The surface of the inlay is processed by providing a groove perpendicular to the side surface of the bottom inlay (1).

5. The method for connecting composite material layers according to claim 4, characterized in that, The bottom layer comprises a web (3), and the manufacturing of the bottom layer comprises: a first step of connecting the bottom layer insert (1) to the web (3) to form a web frame; a second step of filling the web frame with a core material (6) to form a core mold; and a third step of performing injection molding of the core mold to complete the manufacturing of the bottom layer.

6. The method for connecting layers of a composite material according to claim 5, characterized in that, The bottom layer insert (1) and the web (3) are connected by integrated molding or step-by-step molding.

7. The method for connecting composite material layers according to claim 6, characterized in that, The web (3) and the bottom layer insert (1) are connected by integrated molding, comprising the following steps: Step 1: Winding glass fiber yarn or prepreg in a direction perpendicular to the surface of the bottom insert (1) to fill the groove on the surface of the bottom insert (1), and then continuing to wind glass fiber cloth or prepreg of different widths along the same direction on the surface of the bottom insert (1) until the depression of the bottom insert (1) is filled; Step 2: implanting the bottom insert (1) into the web preform; Step 3: orthogonally lay the fiber fabric, lay the release cloth and the guide net in sequence, and complete the molding of the web (3) through a molding process.

8. The method for connecting composite material layers according to claim 6, characterized in that, The connection between the web (3) and the bottom layer insert (1) is formed in steps, including the following steps: Step 1: Use sandpaper to roughen the fixing surface between the web (3) and the bottom insert (1), and remove dust from the surface of the web (3); Step 2: sandblasting the connection area between the bottom insert (1) and the web (3), and bonding and fixing them with adhesive; Step 3: The fiber fabric is orthogonally laid in the bonding area between the bottom insert (1) and the web (3), with the bottom insert (1) being located between the fiber fabric and the web (3), and then a release cloth and a guide net are laid, and finally the bag film is sealed and vacuum-assisted molding is performed to form a bottom insert fixed composite material (2), thereby completing the fixation of the bottom insert (1).

9. The method for connecting composite material layers according to claim 1, characterized in that, When performing step 2 to lay the surface fiber fabric on the bottom surface, a hole is opened in the surface fiber fabric at the bottom layer insert (1), and the surface insert (5) passes through the hole until the stacking height of the surface fiber fabric is consistent with the height of the surface insert (5) protruding from the bottom layer; the surface fiber fabric laid subsequently is no longer opened.

10. The method for connecting composite material layers according to claim 9, characterized in that, The opening shape is a straight hole, and the opening directions of two adjacent layers of fabric are perpendicular.

11. A composite material, characterized in that, The composite material is fabricated by using the composite material interlayer connection method according to any one of claims 1-10.

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