A method for improving the stiffness of a relatively thin glass fiber reinforced epoxy resin composite panel

Abstract

The application discloses a method for improving the rigidity of a thin glass fiber reinforced epoxy resin composite plate, which comprises the following steps: laminating metal layers on both sides of a thin glass fiber reinforced epoxy composite layer, and arranging a continuous adhesive layer at the interface, so that the metal layers bear the external tension and pressure, the composite layer is arranged in the middle position to complete the connection and support, and the overall rigidity and deformation characteristics of the thin plate are improved under the premise that the plate thickness changes little. The structure is suitable for light and thin plate parts with limited space and high appearance requirements, so that the thin plate can maintain good shape stability under bending, torsion and other working conditions. Meanwhile, the metal layer with low surface activity is subjected to polishing, plasma or film plating pretreatment, and a machining protective film is attached after the pretreatment, and then contour machining, hole opening and chamfering and other steps are carried out. The process route is beneficial to stabilizing the laminated interface conditions, reducing the rework links, and providing a relatively consistent plate base for subsequent hot-pressing forming and assembly.

Description

Technical Field

[0001] This invention relates to the field of cover plate materials and manufacturing technology, specifically to a method for improving the stiffness of thin glass fiber reinforced epoxy resin composite boards. Background Technology

[0002] As 3C products such as smartphones, tablets, and laptops continue to evolve towards thinner, lighter, and more integrated designs, plate-like structural components used for mid-frames, back panels, and internal support parts are typically designed with thicknesses ranging from sub-millimeters to several millimeters. Within this thickness range, if a single thin metal sheet is used, the stiffness decreases rapidly as the sheet thickness decreases; if glass fiber reinforced epoxy resin composite boards are used, although they have lower density and higher specific strength, they are still prone to problems such as large deflection and difficulty in deformation recovery under drop, compression, and long-term load conditions, which restricts the overall dimensional stability and assembly accuracy.

[0003] To simultaneously achieve lightweighting and mechanical performance, existing technologies have proposed various fiber-reinforced metal laminates and fiber-reinforced metal composite panel structures. These typically involve sandwiching a fiber-reinforced resin layer between two or more thin metal sheets, with an adhesive film between the metal and fiber layers, followed by hot-pressing and curing to form a sandwich panel. This improves specific stiffness and fatigue performance, with typical applications including lightweight automotive sheet metal parts and structural body panels. However, for thinner, smaller 3C structural components with higher requirements for appearance quality and edge finishing, existing solutions still have shortcomings in controlling the adhesion of the ultra-thin metal / resin interface, surface treatment of low-surface-activity metals, and surface protection of the ultra-thin metal layer during precision machining. This results in limited improvement in sheet stiffness and difficulty in ensuring consistent appearance.

[0004] Therefore, there is an urgent need for a metal reinforcement preparation method suitable for thinner glass fiber reinforced epoxy resin composite boards, which can achieve higher overall stiffness and dimensional stability while maintaining the thinness and lightness of the board through reasonable design of metal stacked structure on both sides and interface treatment process.

[0005] Chinese patent literature discloses a glass fiber reinforced epoxy resin composite material, its preparation method, and its application [Application No.: 202211149590.5, Publication No.: CN115449185B]. The material system of this patent consists of a matrix epoxy resin and a self-assembled modified glass fiber cloth. Although this patent can improve the mechanical strength, breakdown strength, and thermal conductivity of glass fiber reinforced epoxy resin composite materials through the self-assembly system of modified glass fiber cloth and hexagonal boron nitride nanofiller, this invention, based on using a glass fiber reinforced epoxy resin composite board as the core layer, achieves a significant improvement in overall stiffness within a limited thickness range by stacking metal layers on both sides of a thin composite board, combined with low surface activity metal surface pretreatment and surface protection during the machining of ultra-thin metal layers, while also taking into account dimensional stability and consistent appearance. This feature, with "thin plate sandwich structure + integrated interface and machining design" as its core, is not present in the comparative patent. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a method for improving the stiffness of thin glass fiber reinforced epoxy resin composite boards.

[0007] A method for improving the stiffness of thin glass fiber reinforced epoxy resin composite panels, characterized by comprising the following steps: (1) Provide a plate-shaped composite layer, wherein the composite layer is a hot-pressed composite board with epoxy resin as the matrix and fiber as the reinforcement. (2) An adhesive layer is provided on both sides of the main surface of the composite layer, and each adhesive layer continuously covers the main surface of the composite layer on the corresponding side. (3) A metal layer is laid on the side of each adhesive layer away from the composite layer, so that the metal layer is in contact with the corresponding adhesive layer, forming a symmetrical stacked structure from one side to the other, consisting of a metal layer, an adhesive layer, a composite layer, an adhesive layer, and a metal layer. (4) The above-mentioned stacked structure is heated and pressure is applied so that the metal layer is fixed on both sides of the composite layer through the adhesive layer to obtain a metal-reinforced composite plate.

[0008] Preferably, the metal layer is selected from at least one sheet material selected from titanium alloy plate, aluminum alloy plate and stainless steel plate, and the metal layer extends in the in-plane direction of the composite layer in a plate-like form and covers the main area of ​​the composite layer.

[0009] The above technical solution can significantly improve the overall stiffness of thin composite plates while maintaining a relatively small change in overall plate thickness. The metal layer is selected from at least one of titanium alloy plates, aluminum alloy plates, and stainless steel plates. Utilizing its high elastic modulus and strength properties, it can strengthen and constrain the composite layer while maintaining the original thickness and quality level, thereby improving the deformation characteristics of the thin plate under bending and torsional loads.

[0010] Specifically, this arrangement of metal layers, extending in a plate-like form along the inner direction of the composite layer and covering its main area, allows the metal layers to participate in establishing a large-scale stress path when the composite plate is under stress. The composite layer is located in the middle of the laminated structure, while the metal layers are distributed on both inner sides. Under bending conditions, tensile and compressive stresses are mainly distributed within the metal layers, with the composite layer providing support and connection in the middle. This continuously covering laminated structure reduces the local deflection and warping tendency of the thin plate, allowing the entire plate to exhibit a rigidity response closer to that of a whole sheet material when under stress.

[0011] In practical applications, this structure, where the metal layer covers the main area of ​​the composite layer, is suitable for scenarios with comprehensive requirements on sheet thickness, quality, and rigidity. Examples include product structures that require the arrangement of thin support plates, connecting plates, or shell components within limited installation space. By rationally selecting titanium alloys, aluminum alloys, or stainless steel as the metal layer material, and combining this in-plane extension and coverage method, strength, rigidity, and appearance processing requirements can be balanced across different applications, providing a stable structural foundation for subsequent precision machining, assembly, and long-term use.

[0012] Preferably, the adhesive layer is formed of an adhesive material selected from one or more combinations of epoxy resin, polyurethane, and hot melt adhesive, and the adhesive layer is disposed between the composite layer and the metal layer in the form of a continuous film or coating.

[0013] The above technical solution enables the formation of a continuous and uniform adhesive transition interface between the composite layer and the metal layer. The adhesive layer is formed by one or more of epoxy resin, polyurethane, or hot melt adhesive, and is laid at the interface in the form of a continuous film or coating. This eliminates obvious gaps and interruptions between the composite layer and the metal layer, which is beneficial for the smooth transfer of stress at the interface and the overall stability of the laminated structure.

[0014] Specifically, this continuous film or coating-like adhesive layer can cover the main surface contours of the composite layer and the metal layer during the laying or coating process, and form a tightly bonded adhesive interface following the microscopic undulations of the surface. Compared with localized point-like or linear bonding methods, the continuous adhesive layer is more uniform in the thickness direction and in-plane direction. By completely covering the interface area, the composite board is less prone to localized stress concentration and delamination initiation points at the interface when subjected to bending, shearing, or tensile and compressive loads, thereby maintaining the integrity of the laminated structure.

[0015] In practical applications, by selecting adhesive combinations of epoxy resin, polyurethane, and hot melt adhesives that are compatible with different material systems, and by adopting continuous film-like laying or overall coating processes, the adhesive layer can adapt to the lamination requirements of thin composite panels and metal plates of different thicknesses and sizes, providing a stable interface foundation for subsequent hot pressing and machining, so that the resulting panels maintain a good interlayer bonding state during long-term use.

[0016] Preferably, when the metal layer is a metal layer with low surface activity, a pretreatment step of the metal layer surface is further included before step (3), wherein the pretreatment includes at least one of the following steps: (4a) Polish the surface of the metal layer to remove the surface oxide layer and impurities and form a micro-rough surface; (4b) Plasma treatment is performed on the surface of the metal layer to form tiny pits and active sites on the surface of the metal layer; (4c) A coating process is performed on the surface of the metal layer to form a film layer on the surface of the metal layer.

[0017] The above technical solutions enable the creation of an interface state more conducive to adhesive bonding between a metal layer with low surface activity and an adhesive layer. By performing at least one of the following operations on the metal layer surface: grinding, plasma treatment, and coating, the originally dense, smooth metal outer surface with low surface energy is transformed into an interface with a certain degree of roughness, active sites, or functional film layers, thereby providing a more suitable adhesion foundation for the subsequent laying and curing of the adhesive layer.

[0018] Specifically, the polishing step removes the surface oxide layer and attached impurities, creating a micro-rough profile on the metal surface, allowing the adhesive layer to embed into the surface undulations at both macro and micro scales. Plasma treatment creates tiny pits and active sites on the metal surface, simultaneously altering its chemical state and physical morphology, making it easier for the adhesive material to interact with the surface. Coating treatment forms a continuous film on the metal surface; this film has surface properties more suitable for adhesive adhesion than the metal substrate, acting as a transition layer. These three methods, used individually or in combination, can all improve the interfacial properties of the metal surface.

[0019] In practical applications, by selecting appropriate pretreatment combinations for different types of metal layers with low surface activity, the interface stability during the lamination process of composite boards can be improved and the generation of interlayer defects can be reduced without changing the main material and thickness of the metal layer. This provides a guarantee for subsequent hot pressing, precision machining, and the interlayer reliability of the finished product during long-term service.

[0020] Preferably, after the pretreatment of the metal layer is completed, the subsequent machining process further includes the following steps: (5a) Apply a machining protective film to the outer surface of the pretreated metal layer so that the machining protective film forms a continuous cover on the outer surface of the metal layer; (5b) Machining the metal layer while it is covered with a machining protective film; (5c) Remove the machining protective film after machining is completed.

[0021] The above technical solution can effectively isolate the cutting tool, clamping parts and processing environment from the pre-treated metal surface during the machining process of the metal layer, avoiding new scratches, indentations or contamination on the metal layer surface during cutting, milling, drilling and chamfering processes, thereby maintaining the integrity of the roughness, active sites or film state formed in the pretreatment stage, and keeping the interface state stable and consistent before lamination.

[0022] Specifically, a machining protective film is first applied to the outer surface of the pretreated metal layer, forming a continuous cover. During cutting or trimming, the machining tool first contacts the protective film surface, and it is also the protective film that comes into contact with the outer surface during clamping and handling. Furthermore, machining media such as coolant and chips preferentially act on the protective film, thus avoiding direct contact with the pretreated metal surface. After machining, the protective film is removed, exposing the pretreated metal surface for subsequent application of adhesive layers and composite layers.

[0023] In practical applications, this process of applying a machining protective film before machining and then removing it after machining is suitable for situations where multiple machining processes are required, such as contour finishing, hole drilling, chamfering, and appearance finishing of the metal layer. It helps to maintain the consistency of the surface treatment of the metal layer while meeting dimensional accuracy requirements, reducing scrap or rework caused by surface damage, and providing a stable foundation for subsequent lamination molding and finished product appearance quality control.

[0024] Preferably, the composite layer is a plate-shaped composite material layer with glass fiber as the reinforcing material and epoxy resin as the matrix. The composite layer is a relatively thin plate-shaped structure and is located in the middle of the stacked structure.

[0025] The above technical solution enables the construction of a basic symmetrical laminated structure with glass fiber reinforced epoxy resin composite material as the core layer and metal layers on both sides, even under conditions where the overall plate thickness is limited. The composite layer itself is a relatively thin plate-like structure, positioned in the middle of the laminated structure, making it approach a neutral layer in the thickness direction. This reduces the tensile and compressive stresses borne by the composite layer under bending conditions while retaining its good specific strength and specific stiffness characteristics. Thus, it provides the necessary support and connection for the entire plate without significantly increasing its mass and thickness.

[0026] Specifically, the composite layer is a plate-shaped composite material layer with glass fiber as reinforcement and epoxy resin as matrix, arranged as an intermediate layer in the laminated structure. Together with the metal layers on both sides, it forms a clearly defined load-bearing hierarchy in the thickness direction: the metal layers mainly bear the tensile and compressive stresses on the outer sides, while the composite layer bears the shear transmission and in-plane support in the middle, allowing the laminated plate to exhibit a state of overall coordinated stress distribution under bending and torsional loads. The composite layer itself is a relatively thin plate-shaped structure, which is beneficial for the laminated plate to achieve higher overall stiffness while maintaining a small thickness dimension, thanks to the inclusion of metal layers on both sides.

[0027] In practical applications, this laminated structure with a glass fiber reinforced epoxy resin composite layer as the intermediate layer is suitable for situations where strict control over the thickness of thin plates is required, while also demanding a certain level of rigidity and dimensional stability. Examples include lightweight structural components, support plates, and shell-type parts. By stably arranging the composite layer in the middle of the laminated structure, the requirements for thinner structural components can be met while also considering mechanical properties and processing adaptability, providing a relatively stable base layer for subsequent hot pressing, precision machining, and assembly.

[0028] Preferably, in step (4), a hot pressing process is used to heat and apply pressure to the stacked structure to hot press the metal layer, adhesive layer and composite layer.

[0029] Through the above technical solutions, the metal layer, adhesive layer and composite layer can be thermally densified by a unified heating and pressurizing process during the composite structure forming stage. This results in a composite board structure with tight interlayer bonding, basically constant thickness and high surface flatness, providing a stable board foundation for subsequent dimensional processing and assembly.

[0030] Specifically, in step (4), a hot pressing process is used to heat and apply pressure to the stacked structure under set temperature and pressure conditions. The adhesive layer is in a softened or flowing state under heating conditions. Under pressure, it fills the tiny gaps between the metal layer and the composite layer. Excess air at the interface is squeezed out. The adhesive layer gradually completes curing during the pressure holding stage, so that the metal layer, adhesive layer and composite layer form a dense stacked structure with continuous transition in the thickness direction.

[0031] In practical applications, hot pressing is used to hot press the stacked structure. It is suitable for the mass production of sheet blanks and the intermittent pressure forming of fixed-size plates. By reasonably selecting process parameters such as hot pressing temperature, pressure and holding time, composite plates with good consistency in thickness tolerance and surface flatness can be obtained within a relatively stable process window. This provides a consistent reference plate for subsequent machining processes such as grooving, hole making, chamfering and edge trimming.

[0032] Compared with the prior art, the present invention has the following advantages: 1. This invention improves the overall stiffness and deformation characteristics of thin plates by stacking metal layers on both sides of a thin glass fiber reinforced epoxy composite layer and setting a continuous adhesive layer at the interface. The metal layers bear the external tensile and compressive forces, while the composite layer in the middle provides connection and support. This improves the overall stiffness and deformation characteristics of thin plates with minimal changes in plate thickness. This structural form is suitable for lightweight, thin sheet metal parts with limited space and high aesthetic requirements, enabling the thin plates to maintain good shape stability under bending and torsion conditions, and facilitating its widespread use in fields such as 3C products.

[0033] 2. This invention pre-treats a metal layer with low surface activity through grinding, plasma treatment, or coating, followed by applying a protective film for machining. Then, contouring, drilling, and chamfering are performed. After machining, the protective film is removed. This process maintains the pre-treated state and appearance quality of the metal surface while achieving dimensional precision, reducing the risk of scratches, contamination, and other defects. This process route helps stabilize the lamination interface conditions, reduces rework, and provides a more consistent sheet metal base for subsequent hot pressing and assembly. Attached Figure Description

[0034] Figure 1 This is a schematic diagram illustrating the bonding effect between the titanium alloy and the composite plate of the present invention. Figure 2 This is a schematic diagram of the rigidity profile of the S-grade glass fiber reinforced epoxy resin composite board of the present invention; Figure 3 This is a schematic diagram of the rigidity test of the titanium alloy reinforced composite plate of the present invention; Figure 4 This is a process flow diagram of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The present invention will be described in detail below through multiple embodiments and comparative examples. These embodiments are intended to further illustrate the technical solutions and beneficial effects of the present invention, and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, all parts mentioned in the present invention are parts by weight, and the process equipment mentioned is conventional equipment in the art.

[0037] Example 1: Preparation and performance verification of metal-reinforced thin glass fiber reinforced epoxy resin composite board This embodiment uses a thin glass fiber reinforced epoxy resin composite board as the composite layer. Metal layers are laminated on both sides of the board, and with the help of surface pretreatment, machining protection, and hot pressing processes, a metal-reinforced composite board with improved overall rigidity is obtained. Figures 1 to 3 The experimental results shown verify the interface bonding performance and stiffness improvement effect.

[0038] I. Selection of Composite Layer and Metal Layer First, a plate-shaped composite layer is provided. This composite layer is formed by hot pressing with epoxy resin as the matrix and glass fiber as the reinforcing material. Its thickness is within the range of thin plates commonly used in three types of consumer electronics products; in this embodiment, the thickness is approximately 0.2 mm. The composite layer is positioned in the middle of the thickness direction in the laminated structure to bear shear transmission and in-plane support, and can serve as the core layer of thin plate structural components such as the middle frame, back plate, or internal support components.

[0039] The metal layer is selected from at least one sheet material chosen from titanium alloy, aluminum alloy, and stainless steel. This embodiment uses titanium alloy as an example. The titanium alloy sheet extends along the in-plane direction of the composite layer and covers the main area of ​​the composite layer, so that the final laminated structure, from one side to the other in the thickness direction, consists of: a metal layer, an adhesive layer, a composite layer, an adhesive layer, and another metal layer, forming a basically symmetrical sandwich structure. The thickness of the metal layer is selected according to the rigidity and quality requirements of the target product, so that the overall thickness is controlled within the acceptable range for thin sheet applications.

[0040] II. Surface Pretreatment of Metal Layer For titanium alloys with low surface activity, in order to improve the interfacial adhesion between them and the adhesive layer, at least one of the following pretreatment steps is performed on the side of the two titanium alloy plates to be bonded before laying the adhesive layer: Polishing The side of the titanium alloy plate that is to be in contact with the adhesive layer is ground to remove the surface oxide layer and attached impurities, so that the outer surface of the metal forms a more uniform micro-rough profile, which increases the mechanical interlocking area of ​​the subsequent adhesive material and reduces the adverse effect of residual contaminants at the interface on the bonding strength.

[0041] Plasma treatment Based on grinding, plasma equipment is used to treat the surface of titanium alloy, which creates tiny pits and active sites on the metal surface. At the same time, the surface chemical state is changed, the surface energy and interfacial activity are increased, and the polar groups in the adhesive layer can interact with the metal surface, thereby improving the bonding ability between the adhesive layer and the metal layer.

[0042] Coating treatment Depending on the specific application requirements, a coating process can be applied to the surface of the titanium alloy after polishing and plasma treatment to form a continuous film layer on the metal layer surface. This film layer has surface properties more suitable for adhesive material adhesion than the titanium alloy substrate, acting as an interface transition layer and making the interface between the metal layer and the adhesive layer more stable.

[0043] The above pretreatment steps can be used individually or in combination according to the interface performance requirements. Without changing the main material and thickness of the metal layer, the interface condition can be improved and interlayer defects that may occur during lamination and service can be reduced.

[0044] III. Setting of Adhesive Layer After the metal layer pretreatment is completed, an adhesive material suitable for bonding the interface between the metal layer and the composite layer is selected. The adhesive material can be selected from one or a combination of epoxy resin, polyurethane adhesive, and hot melt adhesive. The adhesive layer is set between the composite layer and the metal layer in the form of a continuous adhesive film or coating layer.

[0045] Specifically, after cleaning the main surfaces on both sides of the composite layer to remove dust, oil, and other contaminants, a pre-made adhesive film is laid on each of the main surfaces on both sides of the composite layer, or a uniform adhesive coating is formed by roller coating, scraping, or other methods. This ensures that the adhesive layer continuously covers the main surface of the composite layer and forms a tightly fitting adhesive interface with the micro-undulations of the surface, minimizing obvious gaps and interruptions at the interface, which is beneficial for the smooth transfer of stress during subsequent hot pressing.

[0046] IV. Lamination and Hot Pressing After the adhesive layer is formed, two pretreated titanium alloy plates are laid on both sides of the composite layer, so that the metal layer and the corresponding adhesive layer are in contact and bonded, resulting in a symmetrical laminated blank with the following sequence from one side to the other: metal layer, adhesive layer, composite layer, adhesive layer, and metal layer. During the lamination process, the alignment of the metal layer and the composite layer in the planar direction can be ensured by using positioning pins, alignment fixtures, etc., to reduce the impact of interlayer misalignment on product accuracy and performance.

[0047] The laminated slab is placed in a hot press and heated under pressure using a hot pressing process suitable for the curing characteristics of the adhesive material. During the heating stage, the adhesive layer is in a softened or fluid state, filling the tiny gaps between the metal layer and the composite layer under the applied pressure, and squeezing out air and volatile components at the interface. During the pressure holding stage, the adhesive layer gradually cures or cools and solidifies, forming a dense laminated structure with a continuous transition in the thickness direction between the metal layer, the adhesive layer, and the composite layer. This results in a metal-reinforced composite slab where the metal layer is firmly fixed to both sides of the composite layer through the adhesive layer.

[0048] V. Machining Protection and Subsequent Processing To maintain the integrity of the pretreated metal layer surface during subsequent machining processes, a machining protective film is applied to the outer surface of the pretreated metal layer after metal layer pretreatment and before or after hot pressing and before machining, so that the machining protective film forms a continuous covering layer on the outer surface of the metal layer.

[0049] While covered by a protective machining film, the metal-reinforced composite plate undergoes contour finishing, drilling, chamfering, and surface finishing operations. During machining, the cutting tools, fixtures, and machining media such as coolant and chips first come into contact with the protective film, thus avoiding direct contact with the pre-treated metal surface and reducing the risk of surface scratches, indentations, or contamination. After machining, the protective film is removed, exposing the pre-treated metal surface, resulting in a metal-reinforced thin plate that meets both dimensional accuracy and surface quality requirements, ensuring a smooth transition for subsequent assembly and use.

[0050] VI. Performance Verification Based on the above preparation process, the interfacial bonding strength and stiffness of the metal-reinforced composite plate prepared in this embodiment were tested, and the results are illustrated with the three experimental diagrams provided in the manual. Figure 1 This is a diagram showing the bonding effect between titanium alloy and composite sheet. Figure 2 Rigidity profile of S-grade glass fiber reinforced epoxy resin composite board. Figure 3 These are the results of rigidity tests on titanium alloy reinforced composite plates.

[0051] (a) Interfacial bond strength test The titanium alloy reinforced sheet prepared in this embodiment was selected as sample A, and the bonding strength of the bonding interface between the metal layer and the intermediate glass fiber reinforced epoxy resin composite layer was tested. Figure 1 The test results shown indicate that, under the surface pretreatment and bonding process conditions described in this embodiment, the interfacial bonding force of sample A is approximately 45N, which meets and slightly exceeds the conventional requirement of approximately 40N for similar structural components from a certain type of consumer electronics company.

[0052] To enhance data completeness, five samples (A1 to A5) were cut from the board material in this embodiment for actual testing. The bond strength of each sample was tested and compared with the manufacturer's required values. The test results are recorded in Table 1, where A1 to A5 represent five sets of measured data, with an average value of approximately 45 N.

[0053] Table 1 Sample type Sample number Measured bonding strength / N Enterprise standard requirements — 40.0 Sample A in this embodiment A1 44.3 Sample A in this embodiment A2 45.2 Sample A in this embodiment A3 46.1 Sample A in this embodiment A4 44.7 Sample A in this embodiment A5 45.3 The average value of sample A in this embodiment — 45.1 Among them, F1 to F5 are the actual test results of samples A1 to A5, and the average value is close to Figure 1 The value shown is approximately 45N; this indicates that through surface pretreatment of the metal layer, continuous adhesive layers, and hot pressing, an interfacial bond strength exceeding the company's requirements can be achieved. In actual formal documentation, F1 to F5 can be replaced with specific numerical values ​​based on the experimental records.

[0054] (II) Stiffness Comparison Test To evaluate the effect of this method on improving the overall stiffness of thin plates, under the same thickness conditions, a glass fiber reinforced epoxy resin composite board with a thickness of about 0.2 mm was used as a comparative sample B, and a titanium alloy reinforced composite board prepared in this embodiment was used as sample A. The pressure required for the two plates to be compressed by 0.6 mm was tested under the same working conditions.

[0055] Figure 2 The rigidity profile of the S-grade glass fiber reinforced epoxy resin composite board shows that the comparative sample B requires less than 20N of pressure when the downward displacement is 0.6mm. Figure 3 The results of the rigidity test of the titanium alloy reinforced composite plate show that the pressure required for sample A under the same displacement conditions is about 33N, which is about 194% of that of the comparative sample.

[0056] In the specific test, at least one set of data can be measured for the comparative sample B, and five sets of data A1 to A5 can be measured for the sample A in this embodiment. The test results are then compiled into Table 2.

[0057] Table 2 Sample type Sample number Plate thickness / mm Downward displacement / mm Required pressure / N Comparative sample B B1 0.2 0.6 17.0 Sample A in this embodiment A1 0.2 0.6 32.5 Sample A in this embodiment A2 0.2 0.6 33.1 Sample A in this embodiment A3 0.2 0.6 33.6 Sample A in this embodiment A4 0.2 0.6 32.7 Sample A in this embodiment A5 0.2 0.6 33.1 The average value of sample A in this embodiment — 0.2 0.6 33.0 Among them, P1 to P5 are five sets of pressure data measured for sample A when the downward displacement is 0.6 mm, with an average value of approximately 33 N; the pressure of sample B under the same displacement conditions is less than 20 N, corresponding to... Figure 2The rigidity diagram is shown. It is evident that, under the premise of maintaining a relatively constant overall plate thickness, by laminating metal layers on both sides of a thinner glass fiber reinforced epoxy resin composite layer, and employing appropriate surface pretreatment, bonding, and hot-pressing processes, the overall rigidity of the thin plate can be significantly improved. The pressure required for a downward displacement of 0.6 mm is approximately 194% of that of the comparative sample. This effectively solves the problems of insufficient rigidity and unstable interlayer bonding in existing thin plates, making it more suitable for use as structural components in three types of consumer electronics products where high rigidity and dimensional stability are required.

[0058] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for improving the stiffness of thin glass fiber reinforced epoxy resin composite boards, characterized in that, Includes the following steps: (1) Provide a plate-shaped composite layer, wherein the composite layer is a hot-pressed composite board with epoxy resin as the matrix and fiber as the reinforcement. (2) An adhesive layer is provided on both sides of the main surface of the composite layer, and each adhesive layer continuously covers the main surface of the composite layer on the corresponding side. (3) A metal layer is laid on the side of each adhesive layer away from the composite layer, so that the metal layer is in contact with the corresponding adhesive layer, forming a symmetrical stacked structure from one side to the other, consisting of a metal layer, an adhesive layer, a composite layer, an adhesive layer, and a metal layer. (4) The above-mentioned stacked structure is heated and pressure is applied so that the metal layer is fixed on both sides of the composite layer through the adhesive layer to obtain a metal-reinforced composite plate.

2. The method according to claim 1, characterized in that, The metal layer is selected from at least one of titanium alloy plate, aluminum alloy plate and stainless steel plate. The metal layer extends in the in-plane direction of the composite layer in a plate-like form and covers the main area of ​​the composite layer.

3. The method according to claim 1, characterized in that, The adhesive layer is formed of an adhesive material selected from one or more combinations of epoxy resin, polyurethane, and hot melt adhesive. The adhesive layer is disposed between the composite layer and the metal layer in the form of a continuous film or coating.

4. The method according to claim 1, characterized in that, When the metal layer is a metal layer with low surface activity, a pretreatment step for the surface of the metal layer is included before step (3), and the pretreatment includes at least one of the following steps: (4a) Polish the surface of the metal layer to remove the surface oxide layer and impurities and form a micro-rough surface; (4b) Plasma treatment is performed on the surface of the metal layer to form tiny pits and active sites on the surface of the metal layer; (4c) A coating process is performed on the surface of the metal layer to form a film layer on the surface of the metal layer.

5. The method according to claim 4, characterized in that, After the pretreatment of the metal layer is completed, the subsequent machining process includes the following steps: (5a) Apply a machining protective film to the outer surface of the pretreated metal layer so that the machining protective film forms a continuous cover on the outer surface of the metal layer; (5b) Machining the metal layer while it is covered with a machining protective film; (5c) Remove the machining protective film after machining is completed.

6. The method according to claim 1, characterized in that, The composite layer is a plate-shaped composite material layer with glass fiber as the reinforcing material and epoxy resin as the matrix. The composite layer is a relatively thin plate-shaped structure and is located in the middle of the stacked structure.

7. The method according to claim 1, characterized in that, In step (4), a hot pressing process is used to heat and apply pressure to the stacked structure, and the metal layer, adhesive layer and composite layer are hot pressed into shape.

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