Electronic device shell based on fiber recycling secondary manufacturing and forming process thereof

Abstract

The application discloses an electronic device shell based on fiber recycling secondary manufacturing and a forming process thereof. The electronic device shell comprises a fiber reinforced composite plate and a plastic structural part combined with the fiber reinforced composite plate through an in-mold injection process. The composite plate comprises at least four fiber layers. The preset angle between the fiber laying directions of any two adjacent fiber layers is 0°, ±45° or 90°. The outermost two fiber layers are virgin fiber reinforced layers, and the fiber layer in the middle is a virgin fiber reinforced layer or a recycled fiber reinforced layer. The proportion of the recycled fiber reinforced layer is not less than 20%. The application realizes high reliable structural stability and controllable mechanical properties under the premise of ensuring the light and thin device through a novel solid plate and shell structure design. The application can be directly applied to the intelligent mobile electronic device shell structural part with strict requirements of light and thin, high strength, high reliability and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of composite material molding and electronic device structural component manufacturing technology, and relates to an electronic device housing, particularly to a multi-layer composite solid plate with recycled fibers as the main reinforcement and its housing, as well as a matching thermosetting / thermoplastic dual-route compression molding process. Background Technology

[0002] In recent years, intelligent mobile electronic devices, represented by AI terminals, foldable screen phones, and ultra-thin laptops, have been undergoing unprecedented rapid iteration, driving the continuous development of the entire information technology field. In this process, the market has placed increasingly stringent demands on devices for thinner and lighter designs, higher performance, and environmental adaptability, which has become the core driving force for innovation in the consumer electronics industry. To meet this critical need and effectively reduce device weight, the shell structure design of mobile electronic devices is constantly evolving towards lightweighting. High-performance composite materials, due to their excellent specific strength and specific modulus, have become the core technological focus for achieving this goal.

[0003] Currently, the application of lightweight composite materials in electronic devices is showing a diversified development trend, but each technical approach has certain limitations. For example, while composite structures using carbon fiber sheets and engineering plastics can achieve weight reduction and improved impact resistance through coating processes, the significant differences between carbon fiber and plastic in key physicochemical properties such as coefficient of thermal expansion, elastic modulus, and surface energy make them prone to insufficient interfacial bonding during processes like in-mold molding. This can lead to the plastic layer peeling off from the substrate and delaminating, severely affecting structural stability. Another example is titanium-aluminum gradient composites, which can significantly improve tensile strength by forming an intermetallic compound transition layer through processes like cumulative roll-over welding (ARB) or explosive welding. However, the difference in the coefficients of thermal expansion between the two metals can still trigger microcracks in extreme temperature environments ranging from -40°C to 85°C. This typically requires adding a transition layer of a certain thickness to resist thermal stress, which significantly restricts the design of ultra-thin and lightweight devices. Furthermore, while bio-based composites can significantly reduce material costs by replacing carbon fibers with a higher proportion of natural fibers, their flexural modulus is generally low (typically around 10-15 GPa, though some high-performance natural fiber composites can reach over 15 GPa). Their structural stability and impact resistance still cannot fully meet the stringent requirements of high-end foldable screens, high-performance laptops, and other devices. The latest development in prepreg technology for coated fibers, while optimizing electromagnetic shielding or thermal conductivity by depositing metal coatings on the carbon fiber surface, significantly increases material costs, and there are concerns about the long-term reliability of the interfacial bonding between the coating and the fiber matrix in practical applications.

[0004] In summary, while pursuing the ultimate thinness and lightness of electronic devices, existing technologies generally face key issues such as insufficient interface bonding, risk of microcracks, excessive costs, or insufficient performance, making it difficult to achieve an effective balance between structural stability, mechanical performance, manufacturing costs, and environmental recycling. Summary of the Invention

[0005] This invention provides an electronic device housing based on fiber recycling and secondary manufacturing, and its molding process. It aims to achieve high structural stability and controllable mechanical properties while ensuring the device is lightweight and thin, through a novel solid sheet material and housing structure design.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A fiber-reinforced composite board for electronic devices includes at least four fiber layers, wherein: the fiber laying directions of any two adjacent fiber layers have a preset angle of 0°, ±45° or 90°; all fiber layers are integrally cured into a solid structure by molding with a resin matrix; the two outermost fiber layers are virgin fiber reinforcement layers, and the fiber layer in the middle is either a virgin fiber reinforcement layer or a recycled fiber reinforcement layer, and the proportion of recycled fiber reinforcement layers is not less than 20%.

[0007] A method for preparing the above-mentioned fiber-reinforced composite board for electronic devices includes the following steps: Step 1: Prepreg preparation: Thermosetting prepregs are prepared by hot-melt method and frozen storage, or thermoplastic prepregs are prepared by melt impregnation method or film lamination method and stored at room temperature; Step 2, Cutting and Laying: In a cleanroom environment, lay each fiber layer according to the preset layup order; Step 3, Molding: Place the stacked blanks into a mold for molding and curing; Step 4, CNC precision machining: Machining the shape and structure of the formed sheet metal; Step 5: Clean and dry.

[0008] An electronic device housing based on recycled fiber secondary manufacturing includes the aforementioned fiber-reinforced composite sheet and a plastic structural component integrally formed with the fiber-reinforced composite sheet through an in-mold injection molding process.

[0009] A molding process for the above-mentioned electronic device housing based on fiber recycling and secondary manufacturing includes the following steps: The CNC-machined composite sheet is placed into the injection mold as an insert. The mold cavity is equipped with a double locking structure of V-shaped guide groove and dovetail groove. The insert and the injection molded part are firmly connected through mechanical interlocking. The injection molding process uses high pressure and low speed to form a mechanically interlocked integrated structure to obtain the final shell. The injection pressure is controlled at 5~15MPa.

[0010] Compared with the prior art, the beneficial effects of the present invention are: 1. Technological Innovation: (1) Four to seven layers of orthogonal symmetrical layup integral molding. The 0° / 90° orthogonal alternating layup design is adopted, and the number of layers can be selected as four, five, six or seven. All fiber layers are co-cured by molding in one step with resin matrix. This structure balances the in-plane bidirectional mechanical properties, eliminates weak interfaces between layers, and significantly improves bending stiffness and anti-delamination ability.

[0011] (2) "Native-coated recycled" gradient laying process. The surface layer uses continuous virgin carbon fiber to ensure appearance and high modulus, while the inner layer is filled with a large amount of recycled carbon fiber, recycled glass fiber or bamboo fiber felt, with the recycled fiber accounting for no less than 20% of the mass. Through independent material selection and thickness control of each layer, a gradient transition of stiffness from the surface layer to the core layer is achieved.

[0012] (3) Thermosetting / thermoplastic dual-route compatible rapid prototyping. It is compatible with both thermosetting medium-temperature epoxy systems (preheating and degassing → staged pressurization → controlled cooling, cycle ≤30min) and thermoplastic systems (PC / PP / PA melt hot pressing, cycle 10~90 seconds). Thermoplastic product scraps can be directly recycled and granulated, reducing carbon at both the production and waste ends.

[0013] 2. Materials Innovation: (1) A resource recycling system with recycled fibers as the main body and virgin fibers as the outer layer. The inner layer mainly consists of recycled carbon fiber (pyrolysis to recover chopped filaments and production waste), recycled glass fiber, bamboo fiber and other secondary resources, while the outer layer is covered with a small amount of virgin carbon fiber. The sources of recycled fibers include retired wind turbine blades, carbon fiber waste and other materials, which greatly reduces the virgin carbon footprint.

[0014] (2) Gradient material design with replaceable core layer function. The core layer (third fiber layer) can be flexibly replaced according to product requirements: bamboo fiber + virgin carbon fiber blend to reduce carbon and increase toughness, glass fiber to reduce cost and improve electrical insulation, and recycled carbon fiber needle-punched felt to enhance energy absorption and toughness. The transition layers (second and fourth layers) use recycled carbon fiber / glass fiber to balance lateral reinforcement and cost.

[0015] (3) Recyclable solution for thermoplastic resin matrix throughout its entire life cycle. Thermoplastic sheets with PC, PP, and PA as the matrix can be directly thermo-reformed or pulverized and granulated after being scrapped, and the fibers and resins are recycled simultaneously. Thermosetting epoxy sheets can be recycled by pyrolysis after being scrapped, forming an end-of-life recycling path.

[0016] 3. This invention significantly improves bending and impact resistance by interleaving four to seven layers of fiber with resin and co-curing them, thus avoiding delamination and cracking; it supports combinations of various materials such as carbon fiber, ceramics, and titanium-aluminum to meet diverse needs such as 5G shielding, heat dissipation, and environmental protection.

[0017] 4. The electronic device housing based on the secondary manufacturing of recycled fibers can be directly applied to the structural components of smart mobile electronic devices with stringent requirements for thinness, high strength, high reliability and environmental protection, including but not limited to: back covers and hinge covers of foldable screen phones, A / C / D shells of high-end / thin laptops, back covers of tablet computers, back panels of e-readers, bodies of drones and housings of wearable devices, etc., providing an engineering mass production path for lightweighting, weight reduction and low-carbon circular manufacturing in the consumer electronics industry. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the electronic device housing.

[0020] Figure 2 for Figure 1 A schematic diagram of the AA cross-section structure.

[0021] Figure 3 This is a flowchart illustrating the preparation process of fiber-reinforced composite panels for electronic devices.

[0022] Figure 4 This is a schematic diagram of the electronic device housing in Example 1.

[0023] Figure 5 This is a schematic diagram of the electronic device housing in Example 2.

[0024] Figure 6 This is a schematic diagram of the electronic device housing in Example 3.

[0025] Figure 7 This is a schematic diagram of the electronic device housing in Example 4.

[0026] Figure 8 This is a schematic diagram of the electronic device housing in Example 5.

[0027] Figure 9 This is a schematic diagram of the electronic device housing in Example 6.

[0028] Figure 10 This is a schematic diagram of the electronic device housing in Example 7.

[0029] Figure 11 This is a schematic diagram of the electronic device housing in Example 8.

[0030] Figure 12 This is a schematic diagram of the electronic device housing in Example 9.

[0031] Figure 13 This is a schematic diagram of the electronic device housing in Example 10.

[0032] Figure 14 This is a schematic diagram of the electronic device housing in Example 11.

[0033] Figure 15 This is a schematic diagram of the electronic device housing in Example 12.

[0034] Figure 16 This is a schematic diagram of the electronic device housing in Example 13.

[0035] Figure 17 This is a schematic diagram of the electronic device housing in Example 14.

[0036] Figure 18 This is a schematic diagram of the electronic device housing in Example 15.

[0037] Figure 19 This is a schematic diagram of the electronic device housing in Example 16.

[0038] Figure 20 This is a schematic diagram of the electronic device housing in Example 17.

[0039] Figure 21 This is a schematic diagram of the electronic device housing in Example 18.

[0040] Figure 22 This is a schematic diagram of the electronic device housing in Example 19.

[0041] Figure 23 This is a schematic diagram of the electronic device housing in Example 20. Detailed Implementation

[0042] 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 a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] This invention provides a fiber-reinforced composite board for electronic devices. The fiber-reinforced composite board includes a first fiber layer, a second fiber layer, a third fiber layer, a fourth fiber layer, and optionally a fifth fiber layer, a sixth fiber layer, and a seventh fiber layer, wherein: the fiber laying directions of any two adjacent fiber layers have a preset angle of 0°, ±45°, or 90°; all fiber layers are integrally molded and cured into a solid structure by a resin matrix; the two outermost fiber layers are virgin fiber reinforcement layers, and the proportion of recycled fiber reinforcement layers in all intermediate fiber layers between the two outermost fiber layers is not less than 20%; the virgin fibers in the virgin fiber reinforcement layers are one or more of continuous unidirectional carbon fibers, glass fibers, aramid fibers, or basalt fibers, preferably continuous unidirectional carbon fibers; the recycled fibers in the recycled fiber reinforcement layers are obtained through mechanical crushing, pyrolysis, or chemical recycling treatment, and their morphology includes one or more of chopped fibers, chopped fibers, or nonwoven felt (fibers with no directional distribution).

[0044] In this invention, the total number of fiber layers is four, and the layering order from top to bottom is: the first fiber layer with a fiber direction of 0°, the second fiber layer with a fiber direction of 90°, the third fiber layer, and the fourth fiber layer with a fiber direction of 0°; the first fiber layer, the second fiber layer, and the fourth fiber layer are virgin carbon fiber reinforcement layers, the third fiber layer is a recycled carbon fiber reinforcement layer, and the fibers in the recycled carbon fiber reinforcement layer are short-cut carbon fibers with a length of 6~12mm; the resin matrix is ​​a thermosetting medium-temperature epoxy resin.

[0045] In this invention, the total number of fiber layers is five, and the layering order from top to bottom is as follows: first fiber layer with fiber direction 0°, second fiber layer with fiber direction 90°, third fiber layer with fiber direction 0°, fourth fiber layer with fiber direction 90°, and fifth fiber layer with fiber direction 0°; the first fiber layer, second fiber layer, fourth fiber layer, and fifth fiber layer are virgin carbon fiber reinforcement layers, the third fiber layer is a recycled carbon fiber reinforcement layer, and the recycled carbon fiber is long-cut carbon fiber with a fiber length of 25~50mm; the resin matrix is ​​a thermosetting medium-temperature epoxy resin.

[0046] In this invention, the total number of fiber layers is six, and the layering order from top to bottom is as follows: first fiber layer with fiber direction 0°, second fiber layer with fiber direction 90°, third fiber layer, fourth fiber layer, fifth fiber layer with fiber direction 0°, and sixth fiber layer with fiber direction 90°; the first fiber layer, second fiber layer, fifth fiber layer, and sixth fiber layer are virgin carbon fiber reinforcement layers, the third fiber layer is a recycled carbon fiber felt reinforcement layer, the fourth fiber layer is a recycled carbon fiber reinforcement layer and the fibers are long-cut carbon fibers (fiber length 25~50mm), and the fibers in the third and fourth fiber layers are non-directionally distributed; the resin matrix is ​​thermoplastic polycarbonate.

[0047] In this invention, the total number of fiber layers is seven, and the layering order from top to bottom is as follows: first fiber layer with fiber direction 0°, second fiber layer with fiber direction 90°, third fiber layer with fiber direction 0°, fourth fiber layer, fifth fiber layer with fiber direction 90°, sixth fiber layer with fiber direction 90°, and seventh fiber layer with fiber direction 0°; the first, second, third, fifth, sixth, and seventh fiber layers are virgin carbon fiber reinforcement layers, the fourth fiber layer is a recycled carbon fiber felt reinforcement layer, and the fibers in the recycled carbon fiber felt are non-directionally distributed; the resin matrix is ​​a thermosetting medium-temperature epoxy resin.

[0048] In this invention, the virgin fiber reinforcement layer is made of continuous unidirectional virgin carbon fiber; the thickness of each fiber layer is independently adjustable and is not less than 0.03 mm, and the overall thickness of the composite board is 0.15~0.90 mm.

[0049] In this invention, the resin matrix is ​​either a thermosetting resin or a thermoplastic resin. The thermosetting resin is a thermosetting medium-temperature epoxy resin, and the thermoplastic resin is polycarbonate (PC), polypropylene (PP), polyamide (PA, including PA6 and PA66), or polyetheretherketone (PEEK). When a thermosetting medium-temperature epoxy resin is used, the process parameters for the integral molding and curing are as follows: pre-press at 120~160℃ for 15~30s, followed by venting 1~2 times; then pressurize in stages: pre-press 0.2~1 MPa, main pressure 1~10 MPa, holding pressure 5~8 MPa, and curing time estimated at 1~10 min; demolding is performed by hot demolding or cooling to below 80℃. When a thermoplastic resin is used, the process parameters for the integral molding and curing are as follows: heating to above the resin melting temperature, applying pressure of 1~7 MPa to fuse the fiber layers, holding pressure and cooling to below the resin heat distortion temperature for demolding.

[0050] This invention also provides a method for preparing the above-mentioned fiber-reinforced composite board for electronic devices, such as... Figure 3 As shown, the method includes the following steps: Step 1: Prepreg Preparation: This involves two routes: thermosetting and thermoplastic. Both routes use continuous unidirectional fibers as reinforcement, adhering to the low-carbon principle of virgin outer layers and recycled inner layers. The specific steps are as follows: Thermosetting route: Medium-temperature epoxy resin is used, prepared by hot melt method, resin preheating coating temperature is 70~120℃, composite impregnation temperature is 90~130℃, prepreg resin content is 28~45%, single layer thickness is 0.03~0.12 mm. Thermoplastic route: Prepared by melt impregnation, the resin system can be PP, PA, PC or PEEK, and alternative processes such as solution impregnation, film lamination and powder impregnation can also be used, the single layer thickness is controlled at 0.04~0.13 mm, and the fiber mass content is 55~72%.

[0051] Step 2, Layer Layup: A "virgin-coated-recycled" structure is adopted, with virgin carbon fiber as the outer layer and recycled carbon fiber or plant fiber as the inner layer. The options are: 4-layer scheme: symmetrical layup, total thickness 0.15~0.25 mm; 5-layer scheme: orthogonal alternating symmetrical structure, total thickness 0.15~0.30 mm; 6-layer scheme: symmetrical layup, total thickness 0.20~0.40 mm; 7-layer scheme: symmetrical structure, total thickness 0.25~0.50 mm.

[0052] Step 3, Compression Molding: The stacked blanks are placed in a mold for compression molding and curing. Compression molding is the core process for solidifying the sheet material, and the process conditions for thermosetting and thermoplastic materials are different.

[0053] Thermosetting compression molding: based on chemical cross-linking of epoxy resin. Pre-compress at 120~160℃ for 15~30s, then degas 1~2 times; subsequently pressurize in stages: pre-compress 0.2~1 MPa, main pressure 1~10 MPa, holding pressure 5~8 MPa, curing time estimated at 1~10min; demold by hot demolding or demolding by cooling to below 80℃.

[0054] Thermoplastic compression molding: Based on a physical melt-cooling process, the molding cycle is short. Heating to above the melt temperature (PP 180~250℃, PA 240~310℃, PC 260~320℃, PEEK 360~420℃), applying 1~7 MPa pressure to fuse, holding pressure and cooling to below the heat distortion temperature for demolding, the product is recyclable.

[0055] Step 4, CNC finishing: Use a five-axis CNC laser-assisted milling machine or diamond-coated tools.

[0056] Step 5: Cleaning and Drying: After CNC machining, the product is put into an ultrasonic automatic cleaning line, using deionized water as the main cleaning solution, and dried with hot air. Plasma or flame surface activation treatment may be performed as needed.

[0057] Table 1 shows a comparison between the molding process of this invention and the traditional process.

[0058] Table 1

[0059] In this invention, the electronic device housing is one of the following: laptop shell, tablet back cover, mobile phone back cover, foldable screen device hinge cover, drone body, e-reader back panel, smart home control panel, wearable device shell, or military handheld device shell.

[0060] In this invention, adjacent fiber layers in the fiber-reinforced composite board are made of different types of fiber materials. The natural color differences of the fiber materials themselves create a multi-layered, multi-colored appearance on the shell surface, eliminating the need for additional decorative coatings. After the shell is scrapped, the thermoplastic resin material it contains can be separated from the fiber and recycled through thermoforming, and the thermosetting resin material it contains can be recycled through pyrolysis to reuse the fiber.

[0061] Example 1: This embodiment uses a thermosetting medium-temperature epoxy resin prepreg route, with a five-layer orthogonal alternating symmetrical layup structure and a total thickness of 0.45~0.65 mm. The specific steps are as follows: Step 1: Prepreg Preparation: This embodiment uses a thermosetting route: medium-temperature epoxy resin is used, prepared by hot-melt method. The resin preheating coating temperature is 80~100℃, the composite impregnation temperature is 60~85℃, and the pressure is 0.3~0.8 MPa. The prepreg resin content is 35~38%, and the single-layer thickness is 0.03~0.10 mm.

[0062] Step 2: Lay out the layers, with the layer sequence from top to bottom as follows: First layer (surface layer): Fiber orientation 0°, reinforcing phase: 0° virgin carbon fiber. Matrix phase: medium-temperature epoxy resin.

[0063] Second layer (inner layer): Reinforcing phase: 90° native carbon fiber.

[0064] The third layer (core layer): recycled carbon fiber - long-cut carbon fiber, fiber length 25~50mm, single layer thickness 0.15~0.30mm.

[0065] Fourth layer (inner layer): Reinforcing phase: 90° native carbon fiber.

[0066] Fifth layer (bottom layer): Reinforcing phase: 0° native carbon fiber.

[0067] Step 3, Compression molding: 130~135℃; initial pressure venting 1~2 times; then staged pressure application: pre-pressure 0.2~1MPa, main pressure 7 MPa, holding pressure 5 MPa, curing time estimated at 5min; hot demolding.

[0068] Step 4, CNC finishing: Use a five-axis CNC machining center, PCD or diamond-coated tools, with a cutting edge radius of approximately 0.05 mm.

[0069] Step 5: Cleaning and Drying: After CNC machining, the product is put into an ultrasonic automatic cleaning line, using deionized water as the main cleaning solution, and then dried with hot air.

[0070] Step Six: In-Mold Injection Molding: The precision-machined sheet metal is placed into the injection mold as an insert. The mold cavity has a double-locking structure with V-shaped guide grooves and dovetail grooves (55° angle, 0.6mm depth), achieving a firm connection between the insert and the injection molded part through mechanical interlocking. PC+ABS blend is used for injection molding to form a mechanically interlocked integrated structure, resulting in the final shell.

[0071] Features: Fast curing (molding cycle ≤ 20 min), superior structural stability and impact resistance; Applications: Suitable for products that balance performance and environmental requirements, such as standard tablet back covers and mid-range laptop casings.

[0072] Example 2: This embodiment uses a thermosetting medium-temperature epoxy resin prepreg route with a four-layer layup structure, a total thickness of 0.35~0.6mm, and a density of approximately 1.00~1.70 g / cm³.

[0073] The prepreg preparation still adopts the hot-melt method, and the process parameters are consistent with those in Example 1. The layup sequence from top to bottom is as follows: the first layer (surface layer) is virgin carbon fiber at 0°, the second layer is virgin carbon fiber at 90°, the third layer is recycled carbon fiber—chopped carbon fiber, with a length of 6~12mm and a single layer thickness of 0.10~0.25mm, and the fourth layer is virgin carbon fiber at 0°.

[0074] Compression molding employs a thermosetting process with a curing temperature of 140~160℃ and a curing time of 10 minutes. Subsequent processes, such as CNC precision machining, ultrasonic cleaning, in-mold injection, and appearance inspection, are the same as in Example 1.

[0075] Features: The 4-layer symmetrical layup process is simple and suitable for mass production; the thermosetting epoxy resin system has low curing shrinkage and good dimensional stability; the flame retardancy can reach UL94 V-0 level.

[0076] Applications: Suitable for ultra-thin tablet computer back covers, e-book reader casings, and other products that require high lightweighting and moderate rigidity.

[0077] Example 3: This embodiment employs a thermoplastic melt-impregnated prepreg route, with a six-layer layup structure and a total thickness of 0.60~0.90 mm. It utilizes a multi-material hybrid layup scheme combining carbon fiber felt, virgin carbon fiber prepreg, and recycled plant fibers, with both the top and bottom layers made of virgin carbon fiber.

[0078] Step 1, Prepreg Preparation: This example uses a thermoplastic route: it is prepared by melt impregnation and film lamination, the resin system is PC, and the fiber mass content is 40~68%.

[0079] Step 2, Laying out layers: Follow a symmetrical lay-up design, with angles limited to 0° and 90°, and an overall thickness of 0.60~0.90mm.

[0080] The layer sequence from top to bottom is as follows: First layer (surface layer): Reinforcing phase: 0° virgin carbon fiber. Matrix phase: PC (polycarbonate). Reason: PC has good mechanical properties, dimensional stability, and impact strength. When combined with carbon fiber, it can significantly improve stiffness and strength.

[0081] Second layer (inner layer): Reinforcing phase: 90° native carbon fiber.

[0082] The third layer (inner layer): recycled carbon fiber felt, with a single layer thickness of 0.05~0.26mm.

[0083] Fourth layer (inner layer): recycled carbon fiber - long-cut carbon fiber, fiber length 25~50mm. Fifth layer (inner layer): Fiber orientation 0°, Reinforcing phase: Native carbon fiber. Matrix phase: PC. The rationale for selection is the same as for the third layer.

[0084] Sixth layer (bottom layer): Fiber orientation 90°, reinforcing phase: virgin carbon fiber. Matrix phase: PC. The rationale for selection is the same as for the third layer.

[0085] Step 3, Compression Molding: A thermoplastic compression molding process is used. Based on a physical melt-cooling process, the material is rapidly heated to above the PC melting temperature (280~310℃), and pressure of 2~7 MPa is applied to ensure full fusion of the layers. Then, under pressure holding, it is rapidly cooled to below the heat distortion temperature (approximately 130℃) for demolding. The hot-pressed thickness of the carbon fiber felt / PC composite laminate is ≤1.0 mm, with a fiber content of 60%, a flexural modulus of ≥33 GPa, and it passes the UL94 V-0 flame retardant test, meeting the highest GRS rating. Step 4, CNC Finishing: A five-axis CNC machining center is used with PCD or diamond-coated tools. Cutting parameters: linear speed 450~650 m / min. Dry cutting is supplemented with high-pressure air cooling, and an explosion-proof dust removal system is provided.

[0086] Step 5: Cleaning and Drying: Ultrasonic cleaning using deionized water as the medium. Hot air drying.

[0087] Step Six: In-Mold Injection: The finely machined thermoplastic carbon fiber sheet is placed into the injection mold as an insert. The mold cavity is equipped with a double-locking structure of V-shaped guide groove and dovetail groove (55° angle, 0.6mm depth), which achieves a firm bond between the insert and the injection molded part through mechanical interlocking. The injection molding material is PC and recycled carbon fiber particles.

[0088] Features: Short molding cycle (within minutes, more than 50% shorter than thermosetting composites), prepregs can be stored at room temperature without freezing, simple process and semi-automated production line production; the entire thermoplastic system can be 100% recycled and reshaped, scraps and waste products can be directly recycled and granulated, and the performance retention rate of recycled materials is ≥80%; the recycling rate of multiple material inner layers reaches 45~55%.

[0089] Example 4: This embodiment uses a thermosetting medium-temperature epoxy resin prepreg route, with a seven-layer symmetrical layup structure and a total thickness of 0.60~0.85 mm.

[0090] The prepreg was prepared using the hot-melt method, with the same process parameters as in Example 1.

[0091] The layering sequence from top to bottom is as follows: the first layer (top layer) is virgin carbon fiber at 0°, the second layer is virgin carbon fiber at 90°, the third layer is recycled carbon fiber—short-cut carbon fiber, with a length of 6~12mm and a single layer thickness of 0.10~0.25mm (SMC grade), the fourth layer is recycled carbon fiber felt, with a single layer thickness of 0.02~0.13mm, and the number of layers is 1. The fifth and sixth layers are virgin carbon fiber at 90°. In the seven-layer structure, the fourth layer uses a single layer of carbon fiber felt, which can utilize the isotropic properties of the felt material to improve the interlayer shear strength, while avoiding the risk of thickness deviation and uneven resin impregnation caused by multiple layers of felt. The seventh layer (bottom layer) is virgin carbon fiber at 0°.

[0092] Compression molding employs a thermosetting process, with pre-compression at 140~145℃; initial pressure venting 1~2 times; followed by staged pressure application: pre-compression 1 MPa, main pressure 5 MPa, holding pressure 8 MPa, with an estimated curing time of 3 minutes; and hot demolding. Example 5: The difference between this embodiment and Embodiment 1 is that the third reinforcing phase is recycled carbon fiber felt.

[0093] Example 6: The difference between this embodiment and Embodiment 1 is that the third reinforcing phase is recycled carbon fiber—short-cut.

[0094] Example 7: The difference between this embodiment and Embodiment 3 is that the third reinforcing phase is 0° native carbon fiber. Example 8: The difference between this embodiment and Embodiment 3 is that the fourth reinforcing phase is 0° native carbon fiber. Example 9: The difference between this embodiment and Embodiment 3 is that the third reinforcing phase is recycled carbon fiber-cut short.

[0095] Example 10: The difference between this embodiment and embodiment 3 is that the fourth reinforcing phase is recycled carbon fiber-cut short.

[0096] Example 11: The difference between this embodiment and embodiment 4 is that the third reinforcing phase is 0° native carbon fiber.

[0097] Example 12: The difference between this embodiment and embodiment 4 is that the fifth reinforcing phase is 0° native carbon fiber.

[0098] Example 13: The difference between this embodiment and embodiment 4 is that the third reinforcing phase is 0° native carbon fiber, and the fourth reinforcing phase is long-cut recycled carbon fiber.

[0099] Example 14: The difference between this embodiment and embodiment 4 is that the third reinforcing phase is 0° native carbon fiber, and the fourth reinforcing phase is short-cut recycled carbon fiber.

[0100] Example 15: The difference between this embodiment and embodiment 4 is that the third reinforcing phase is 0° native carbon fiber, and the fifth reinforcing phase is long-cut recycled carbon fiber.

[0101] Example 16: The difference between this embodiment and embodiment 4 is that the third reinforcing phase is 0° native carbon fiber, and the fifth reinforcing phase is 0° native carbon fiber.

[0102] Example 17: The difference between this embodiment and embodiment 4 is that the fifth reinforcing phase is 0° native carbon fiber, and the third reinforcing phase is long-cut recycled carbon fiber.

[0103] Example 18: The difference between this embodiment and embodiment 4 is that the fifth reinforcing phase is 0° native carbon fiber, and the fourth reinforcing phase is long-cut recycled carbon fiber.

[0104] Example 19: The difference between this embodiment and Embodiment 2 is that the third reinforcing phase is recycled carbon fiber felt.

[0105] Example 20: The difference between this embodiment and Embodiment 2 is that the third reinforcing phase is a long cut of recycled carbon fiber.

[0106] The above description is merely an example to clearly illustrate the present invention and is not intended to limit the patent scope of the present invention. It is impossible to exhaustively list all embodiments here. All equivalent structural transformations made using the content of the technical solution of the present invention under the concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A fiber-reinforced composite board for electronic devices, characterized in that... The composite board includes at least four fiber layers, wherein: the fiber laying directions of any two adjacent fiber layers have a preset angle of 0°, ±45° or 90°; the two outermost fiber layers are native fiber reinforcement layers, the fiber layer in the middle is a native fiber reinforcement layer or a recycled fiber reinforcement layer, and the number of recycled fiber reinforcement layers accounts for not less than 20%.

2. The fiber-reinforced composite board for electronic devices according to claim 1, characterized in that... The virgin fiber in the virgin fiber reinforcement layer is one or more of continuous unidirectional carbon fiber, glass fiber, aramid fiber or basalt fiber; the recycled fiber in the recycled fiber reinforcement layer is obtained by mechanical crushing, pyrolysis or chemical recycling, and its form includes one or more of chopped fiber, chopped fiber or nonwoven felt.

3. The fiber-reinforced composite board for electronic devices according to claim 1, characterized in that... The virgin fiber reinforcement layer uses continuous unidirectional virgin carbon fiber; the thickness of each fiber layer is independently adjustable and is not less than 0.03 mm; the overall thickness of the composite board is 0.15~0.90 mm.

4. The fiber-reinforced composite board for electronic devices according to claim 1, characterized in that... The resin matrix is ​​one of thermosetting resin or thermoplastic resin. The thermosetting resin is a thermosetting medium-temperature epoxy resin, and the thermoplastic resin is one or more of polycarbonate, polypropylene, polyamide, and polyetheretherketone.

5. A method for preparing a fiber-reinforced composite board for electronic devices according to any one of claims 1-4, characterized in that... The method includes the following steps: Step 1: Prepreg preparation: Thermosetting prepregs are prepared by hot-melt method and frozen storage, or thermoplastic prepregs are prepared by melt impregnation method or film lamination method and stored at room temperature; Step 2, Cutting and Laying: In a cleanroom environment, lay each fiber layer according to the preset layup order; Step 3, Molding: Place the stacked blanks into a mold for molding and curing; Step 4, CNC precision machining: Machining the shape and structure of the formed sheet metal; Step 5: Clean and dry.

6. The method for preparing fiber-reinforced composite panels for electronic devices according to claim 5, characterized in that... In step one, the thermosetting prepreg uses medium-temperature epoxy resin, prepared by hot-melt method, with resin preheating coating temperature of 70~120℃, composite impregnation temperature of 90~130℃, prepreg resin content of 28~45%, and single layer thickness of 0.03~0.12 mm. When preparing thermoplastic prepreg, the single layer thickness is controlled at 0.04~0.13 mm, and the fiber mass content is 55~72%. In step two, a symmetrical layup design is followed, with an angle of 0° / 90°.

7. The method for preparing fiber-reinforced composite panels for electronic devices according to claim 5, characterized in that... In step three, during thermosetting compression molding, the product is pre-pressed at 120~160℃ for 15~30s and then vented. Staged pressurization is used: pre-press 0.2~1MPa, main pressure 1~10 MPa, holding pressure 5~8 MPa, and curing time estimated at 1~10min. Hot demolding or cooling to below 80℃ is then performed. During thermoplastic compression molding, the product is heated above the melting temperature, subjected to 1~7 MPa pressure for fusion, and then held under pressure and cooled below the heat distortion temperature for demolding. In step four, a five-axis CNC laser-assisted milling machine or diamond-coated tools are used. In step five, the CNC-machined product is fed into an ultrasonic automatic cleaning line, using deionized water as the main cleaning solution, and dried with hot air. Plasma or flame surface activation treatment is performed as needed.

8. An electronic device housing based on secondary manufacturing of recycled fibers, characterized in that... The electronic device housing includes the fiber-reinforced composite sheet for electronic devices as described in any one of claims 1-4, and a plastic structural component integrally formed with the fiber-reinforced composite sheet through an in-mold injection molding process.

9. A molding process for an electronic device housing based on fiber recycling and secondary manufacturing as described in claim 8, characterized in that... The process includes the following steps: The CNC-machined composite sheet is placed into the injection mold as an insert. The mold cavity is equipped with a double-locking structure of V-shaped guide groove and dovetail groove. The insert and the injection molded part are firmly connected through mechanical interlocking. The injection molding process uses high pressure and low speed to form a mechanically interlocked integrated structure to obtain the final shell.

10. The molding process for electronic device housings based on fiber recycling and secondary manufacturing according to claim 9, characterized in that... The double-locking structure has an inclination angle of 55°±5° and a depth of 0.5~0.8mm; the injection pressure is 5~15MPa.

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