Method for integrally forming a fiber-reinforced composite

Abstract

The application discloses a kind of fiber reinforced composite integrated forming method, the method comprises the following steps: step 1, mold preparation;Step 2, material laying;Step 3, primary forming;Step 4, demolding and post-processing.This method solves the technical problems of poor appearance consistency, discontinuous structural mechanics performance and low production efficiency in the existing traditional carbon fiber product forming process, realizes a major breakthrough in carbon fiber product molding / heat pressing primary forming technology, not only guarantees the excellent appearance visual consistency of the product, but also solves the technical problems of four-side flanging side wall and BUMP convex feature integrated forming for the first time in the industry, thus completely optimizing the joint problem between carbon fiber plate and outer frame in traditional process, realizing the double leap of aesthetics and structural integrity, suitable for 3C, notebook computer shell, high-end sports equipment and other products.

Description

Technical Field

[0001] This invention relates to a method for integral molding of carbon fiber products, specifically to a method for integral molding / hot pressing of carbon fiber reinforced composite (CFRP) A Cover. Background Technology

[0002] Carbon fiber reinforced composites, with their superior properties such as lightweight, high strength, corrosion resistance, and high designability, have been widely used in consumer electronics, luxury automobiles, and high-end equipment. These high-end applications place stringent demands on product appearance integrity, structural mechanical properties, and manufacturing efficiency. However, existing traditional carbon fiber product molding processes have many technical shortcomings, making them difficult to adapt to the industrial application needs of high-end fields, as follows: 1. Inconsistent appearance: such as Figure 1 As shown, traditional carbon fiber products mostly adopt the processing mode of "component manufacturing - post-assembly". This processing mode will result in obvious seams, color difference and glue marks, which will destroy the continuity of carbon fiber texture and overall aesthetics, making it difficult to meet the pursuit of ultimate aesthetics in consumer electronics, luxury cars and other fields with strict appearance requirements.

[0003] 2. Weak areas in the structure: In traditional processes, the side walls and protrusions on all four sides are fixed by adhesive or mechanical means. These joints are weak points in the structure and are prone to stress concentration. Long-term use can easily lead to aging, cracking, and detachment. In addition, it destroys the continuous mechanical properties of carbon fiber materials and the core advantages of carbon fiber as "lightweight and high strength".

[0004] 3. Cumbersome manufacturing process: Complex geometric features (such as four-sided flanged sidewalls and convex bulges) usually require secondary or multiple processing, which not only makes the production process cumbersome, inefficient, and costly, but also makes it difficult to control the yield rate.

[0005] 4. Complex structures are difficult to form: Carbon fiber materials have poor fluidity in molds, and defects such as fiber wrinkles, resin enrichment or insufficient filling are very likely to occur on the side walls and the root of the bulge. As a result, such designs have long been regarded as forbidden or have extremely low yield rates.

[0006] In summary, the current market demands higher standards for carbon fiber products, including "functional integration, unified appearance, and high production efficiency." Therefore, a disruptive carbon fiber molding technology is urgently needed that can achieve complex structural features in a single molding process, while simultaneously ensuring both a perfect appearance and structural robustness. Summary of the Invention

[0007] To address the technical challenges of poor appearance consistency, discontinuous structural mechanical properties, and low production efficiency inherent in existing traditional carbon fiber product molding processes, this invention provides a one-piece molding method for fiber-reinforced composite A-cover. This method represents a significant breakthrough in one-time molding technology for carbon fiber products via compression molding / hot pressing. It not only ensures excellent visual consistency but also, for the first time in the industry, overcomes the technical challenge of one-piece molding of the four-sided flanged sidewalls and BUMP bulge features. This completely optimizes the seam problem between the carbon fiber sheet and the outer frame, which is unavoidable in traditional processes, achieving a dual leap in aesthetics and structural integrity. It is applicable to products such as 3C products, laptop casings, and high-end sports equipment.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for integral molding of fiber-reinforced composite materials includes the following steps: Step 1, Mold Preparation: Step 11: According to the product type, manufacture a precision mold with the corresponding shape and structure. The mold cavity directly contains the negative shape of the four-sided flange sidewalls and the negative shape of all BUMP bulges. Step 12: Perform mirror polishing on the forming surface of the mold; Step 2, Material Placement: According to the mold cavity structure, the prepreg is cut into specific shapes and stacked. Step 3, One-time molding: Step 31, Mold Closure and Heating: Place the mold with the prepreg laid on it in the press for mold closure, and control the heating temperature to be 120~160℃ and the pressure to be 0.5~9MPa; Step 32, Resin Flow and Curing: Under pressure, the resin in the prepreg flows and fully fills every corner of the mold. At the same time, the resin undergoes a cross-linking reaction to achieve curing. Step 33, Pressure Holding: Maintain constant pressure during the curing process to ensure product dimensional stability and structural compactness. Control the pressure holding time to 3~60min. Step 4, Demolding and Post-processing: Step 41, CNC: After the mold is opened, the formed product is taken out of the mold cavity and the shape and structure are machined by CNC using a jig. Step 42, Cleaning: Put the CNC-machined product into the ultrasonic automatic cleaning line to clean the dirt off the product surface. Step 43: Inspect the packaging: Inspect the appearance of all products and the dimensions of the sampled products in accordance with the inspection standards.

[0009] Compared with the prior art, the beneficial effects of the present invention are: 1. Solve the aesthetic pain point of "inconsistent appearance": Through one-piece molding, a seamless and continuous surface is achieved from the main body to the side wall and then to the raised bump, ensuring absolute consistency in color, texture and gloss, and achieving the highest aesthetic standards.

[0010] 2. Solving the performance pain point of "weak areas in structure": The integrated structure enables continuous fiber distribution, eliminates mechanical or adhesive connection interfaces, makes force transmission smoother, and greatly improves the overall rigidity, impact resistance and durability of the product.

[0011] 3. Solve the efficiency pain point of "cumbersome manufacturing process": "One-time molding / hot pressing" replaces "multi-step assembly", which greatly simplifies the supply chain and production process, reduces tooling fixtures and manual intervention, significantly improves production efficiency and product consistency, and is more suitable for large-scale mass production.

[0012] 4. Solving the process pain point of "difficult to form complex structures": Through mold design (such as special venting and inserts) and precise process control, the process problem of one-time molding of high-difficulty features has been successfully overcome, realizing complex product designs that were previously impossible.

[0013] Table 1 shows a comparison between the traditional process and the integrated molding process of this invention: Table 1 Attached Figure Description

[0014] Figure 1 It is a traditional processing technique.

[0015] Figure 2 This invention relates to a one-piece molded carbon fiber reinforced composite material shell.

[0016] Figure 3 This is a flowchart of the one-time molding process of the present invention.

[0017] Figure 4 To create a fine-textured appearance.

[0018] Figure 5 To create a rough textured appearance.

[0019] Figure 6 To create the textured appearance.

[0020] Figure 7 It features a UD-style straight-line pattern.

[0021] Figure 8 This is for the structural design and cross-sectional view of the plate material.

[0022] Figure 9 This is the stacking scheme of Example 7.

[0023] Figure 10 This is the stacking scheme of Example 8.

[0024] Figure 11 This is the stacking scheme of Example 9.

[0025] Figure 12 This is the stacking scheme of Example 10.

[0026] Figure 13 This is the stacking scheme of Example 11.

[0027] Figure 14 This is the stacking scheme of Example 12.

[0028] Figure 15 This is the stacking scheme of Example 13.

[0029] Figure 16 This is the stacking scheme of Example 14. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0031] This invention provides a method for integral molding of fiber-reinforced composite materials, such as... Figure 3 As shown, the method includes the following steps: Step 1, Mold Preparation: Step 11: Based on the A Cover product type, use high-strength mold steel to manufacture a precision mold with the corresponding shape and structure. The mold cavity directly contains the negative shape of the four-sided flange sidewalls and the negative shape of all BUMP bulges. Step 12: Perform mirror polishing on the forming surface of the mold to ensure the smoothness of the product's appearance.

[0032] Step 2, Material Preparation and Laying: Step 21: Select a customized fiber-reinforced prepreg with resin content and flowability suitable for complex structure molding. The matrix resin can be one or a combination of thermoplastic resins (petroleum-based thermoplastic resins, bio-based thermoplastic resins) and thermosetting resins (petroleum-based thermosetting resins, bio-based thermosetting resins). The thermosetting resin can be one or more of epoxy resins, polyimide resins, bismaleimide resins, unsaturated polyesters, and vinyl ester resins. The thermoplastic resin can be one or more of PC, PP, PEEK, PA, PA6, and PA66. The fiber can be one or more of carbon fiber, natural fiber, glass fiber, basalt fiber, and special fibers (such as aramid fiber and ultra-high molecular weight polyethylene fiber). Step 22: Based on the three-dimensional cavity structure of the mold, cut the prepreg into a specific shape to fit the complex mold cavity; Step 23: According to the product thickness requirements, multi-angle and multi-layer stacking is carried out to ensure the continuity of fibers on the side walls and bulges and avoid wrinkles. The stacking method adopts the overlapping of unidirectional ply and unidirectional ply, with the ply directions arranged at 0°, ±45° or ±90°, and the local areas are reinforced with special reinforcement.

[0033] Step 3, One-time molding: Step 31, Mold Closure and Heating: Place the mold with the prepreg laid on it in the press and close the mold under precise temperature and pressure control. The temperature is controlled at 100~350℃ and the pressure is controlled at 0.5~13MPa. Step 32, Resin Flow and Curing: Under pressure, the resin in the prepreg flows moderately, fully filling every corner of the mold (including vertical sidewalls and the root of the bump), while heat causes the resin to undergo a cross-linking reaction, thus achieving curing; Step 33, Pressure Holding: Maintain constant pressure during the curing process to ensure product dimensional stability and structural compactness. Control the pressure holding time to 0.5~300min. Preferably, when the matrix resin is epoxy resin, a one-time compression molding process is adopted, with the temperature controlled at 100~160℃, the pressure at 0.5~10MPa, and the holding time at 3~60min; when the matrix resin is polyimide resin, a one-time compression molding process is adopted, with stepped heating, and the temperatures controlled at 180℃~250℃ and 250~300℃ respectively, the pressure at 0.5~10MPa, and the holding times at 10~40min and 30~120min respectively; when the matrix resin is thermoplastic resin, a one-time hot pressing process is adopted, with the temperature controlled at 180~350℃, the molding time at 0.5~300min, and the molding pressure at 0.5~13MPa.

[0034] The above steps, through precise temperature-pressure-time control curves, ensure that the resin achieves perfect flow and curing at right angles and protrusions, thereby simultaneously molding the main body of the product, 90° sidewalls, and functional protrusions within a single molding cycle.

[0035] Step 4, Demolding and Post-processing: Step 41, CNC: After the mold is opened, the formed product is taken out of the mold cavity and the shape and structure are machined by CNC using a special fixture.

[0036] Step 42, Cleaning: Put the CNC-machined product into the ultrasonic automatic cleaning line to clean the dirt off the product surface.

[0037] Step 43: Inspect the packaging: Inspect the appearance of all products and the dimensions of the sampled products in accordance with the inspection standards.

[0038] Seamless integrated structural fiber products prepared by the above methods can be classified into one or more of the following types: all-carbon fiber type, carbon fiber sandwich lightweight type, carbon fiber and glass fiber hybrid type, carbon fiber and glass fiber hybrid sandwich lightweight type, glass fiber type, or basalt fiber type. Among these, the sandwich lightweight type can use one or more of the following core materials: PMI foam, PP plastic, POM foam, PU foam, PVC foam, carbon fiber porous felt, bamboo fiber porous felt, honeycomb PI core material, honeycomb PMI core material, and aramid honeycomb core material, suitable for products such as laptops, smartphones, and drones.

[0039] like Figure 2 As shown, the four sides of the obtained fiber product are seamlessly and continuously connected to the main body, and the BUMP protrusion is continuously and integrally formed with the main fiber, achieving unparalleled visual consistency. The main body, side walls and protrusion of the product all exhibit continuous and uninterrupted fiber weaving texture appearance features, such as one or more combinations of weaving texture, unidirectional texture, carbon fiber texture, special fiber texture and other structures.

[0040] like Figures 4 to 7 As shown, the notebook shells prepared by the above method have diverse appearances, including fine forged texture, coarse forged texture, woven texture, and UD straight texture.

[0041] This invention has the following innovative features: 1. Integrated molding technology: This invention employs high-precision molds and optimized process parameters to enable complex fiber prepregs to simultaneously form the product body, vertical sidewalls, and functional protrusions within a single molding cycle. This transforms the traditional "multi-part assembly" model into an "integral structure growth" model, representing a fundamental change in design and manufacturing concepts.

[0042] 2. Industry First: Flanged Sidewalls and BUMP Protrusions Co-formed: Fiber materials have limited fluidity during molding, easily leading to defects such as fiber wrinkles, resin accumulation, or insufficient filling at the edges, sidewalls, and root of protrusions. This invention, through innovative mold design and precise press control, perfectly replicates these challenging characteristics, demonstrating leading process control capabilities.

[0043] 3. Ultimate visual consistency in appearance: One-piece molding fundamentally eliminates the visual discontinuity caused by component splicing, secondary processing, and adhesive residue. The resulting product has a seamless surface with no color difference, and the fiber weave texture transitions continuously and naturally, presenting a high level of overall aesthetic appeal.

[0044] 4. Structural optimization: Seamless replacement of seams: Aesthetic enhancement: All assembly gaps have been eliminated in appearance, resulting in a clean and sleek design.

[0045] Performance improvement: The structural integrity is greatly enhanced, and the seamless design means there are no potential stress concentration points, which improves the overall rigidity and durability of the product.

[0046] Improved reliability: Avoids quality problems caused by glue aging or loose fasteners.

[0047] 5. Comparison of the value of new and old processes Traditional process: carbon fiber board → separate side frame → glue / mechanical fixation → seams are produced → inconsistent appearance and weak areas in structure.

[0048] The process of this invention is as follows: integral prepreg → molding / hot pressing in one step → seamless one-piece structure → consistent appearance and complete structure.

[0049] The successful development of this fiber molding / hot pressing one-step forming technology not only represents the pinnacle of manufacturing precision but also redefines the quality standards of fiber products. By integrating complex structures, it achieves a perfect appearance for high-end users, superior performance for harsh environments, and improved efficiency for mass production. This technology sets a new industry benchmark for fiber materials in fields with stringent requirements for appearance and structural integrity, such as consumer electronics, high-end automobiles, and medical devices.

[0050] Example 1: Step 1, Mold Preparation: Step 11: Based on the product type of A Cover (laptop / tablet), use high-strength mold steel to manufacture a precision mold with the corresponding shape and structure. The mold cavity directly contains the negative shape of the four-sided flange sidewalls and the negative shape of all BUMP bulges. Step 12: Perform mirror polishing on the forming surface of the mold to ensure the smoothness of the product's appearance.

[0051] Step 2, Material Preparation and Laying: Step 21: Cut the prepreg into specific shapes according to the three-dimensional cavity structure of the mold to fit the complex mold cavity; Step 22: Stack the products at multiple angles and in multiple layers according to the required thickness.

[0052] Step 3, one-time molding: Step 31, Mold Closure and Heating: Place the mold with the prepreg laid on it in the press for mold closure, and control the heating temperature at 150±10° and the pressure at 6±0.5MPa; Step 32, Resin Flow and Curing: Under pressure, the resin in the prepreg flows moderately, fully filling every corner of the mold (including vertical sidewalls and the root of the bump), while heat causes the resin to undergo a cross-linking reaction, thus achieving curing; Step 33, Pressure Holding: Maintain constant pressure during the curing process to ensure product dimensional stability and structural compactness. Control the pressure holding time to 2100±10s.

[0053] Step 4, Demolding and Post-processing: Step 41, CNC: After the mold is opened, the molded product is taken out of the mold cavity and the shape and structure are machined by CNC using a special fixture.

[0054] Step 42, Cleaning: Put the CNC-machined product into the ultrasonic automatic cleaning line to clean the dirt off the product surface.

[0055] Step 43: Inspect the packaging: Inspect the appearance of all products and the dimensions of the sampled products in accordance with the inspection standards.

[0056] Example 2: The difference between this embodiment and embodiment 1 is that the materials are changed based on embodiment 1. The fibers in the prepreg are a mixture of glass fiber and carbon fiber, and the specific mixing ratio is determined according to the product design.

[0057] Example 3: The difference between this embodiment and Embodiment 1 is that the resin and molding process are changed based on Embodiment 1. The resin used is a fast-curing resin (such as epoxy resin), and the resin is rapidly molded and demolded under the conditions of heating temperature of 130°C, pressure of 0.5 MPa, and holding time of 4 min.

[0058] Example 4: The difference between this embodiment and Embodiment 3 is that the resin used is polyimide resin, the temperature is a stepped range of 200℃ and 330℃, the pressure is 5MPa, and the holding time is 20min and 60min respectively.

[0059] Example 5: The difference between this embodiment and embodiment 1 is that the product design shape is changed based on embodiment 1, and thermoplastic PC-based carbon fiber prepreg tape is used as a laminate design. It is rapidly hot-pressed and demolded under the conditions of heating temperature of 230℃, pressure of 5Mpa, and holding time of 100min.

[0060] Example 6: The difference between this embodiment and embodiment 1 is that the layering scheme is changed based on embodiment 1, for example, using 0 / 90, 90 / 0 / 90, or 0 / 45 / 90 / 45 / 0 design.

[0061] Example 7: The difference between this embodiment and Embodiment 1 is that: Figure 8 and Figure 9 As shown, the product as a whole is a single UD (unidirectional carbon fiber) layer.

[0062] Example 8: The difference between this embodiment and embodiment 7 is that: Figure 10 As shown, the internal core is a foam or plastic sandwich layer.

[0063] Example 9: The difference between this embodiment and embodiment 7 is that: Figure 11 As shown, the internal core is a honeycomb sandwich layer.

[0064] Example 10: The difference between this embodiment and Embodiment 1 is that: Figure 8 and Figure 12 As shown, the outer layer of the product is SMC (short-cut carbon fiber or short-cut glass fiber reinforced resin composite material forming irregular forging patterns), and the inner layer is unidirectional carbon fiber (UD).

[0065] Example 11: The difference between this embodiment and embodiment 10 is that: Figure 13 As shown, the internal core is a foam or plastic sandwich layer.

[0066] Example 12: The difference between this embodiment and Embodiment 1 is that: Figure 8 and Figure 14 As shown, the outer layer of the product is 3K twill woven carbon fiber cloth, and the inner layer is unidirectional carbon fiber (UD).

[0067] Example 13: The difference between this embodiment and embodiment 12 is that: Figure 15 As shown, the internal core is a foam or plastic sandwich layer.

[0068] Example 14: The difference between this embodiment and embodiment 1 is that: As... Figure 16 As shown, the product is a combination of glass fiber and basalt, with the inner layer of carbon fiber being unidirectional carbon fiber (UD) laid up at 0 degrees and 90 degrees.

[0069] Example 15: The difference between this embodiment and Embodiment 1 is that the product is a combination of carbon fiber and glass fiber, and the internal core materials are POM and PU foam or plastic core materials, respectively. The inner layer of carbon fiber is unidirectional carbon fiber (UD) laid up at 0 degrees and 90 degrees.

[0070] Example 16: The difference between this embodiment and Embodiment 1 is that the product is a combination of carbon fiber and glass fiber, and the internal core materials are PMI and PP foam or plastic, respectively. The inner layer of carbon fiber is unidirectional carbon fiber (UD) laid up at 0 degrees and 90 degrees and with local reinforcement.

Claims

1. A method for integral molding of fiber-reinforced composite materials, characterized in that... The method includes the following steps: Step 1, Mold Preparation: Step 11: According to the product type, manufacture a precision mold with the corresponding shape and structure. The mold cavity directly contains the negative shape of the four-sided flange sidewalls and the negative shape of all BUMP bulges. Step 12: Perform mirror polishing on the forming surface of the mold; Step 2, Material Placement: According to the mold cavity structure, the fiber-reinforced prepreg is cut into specific shapes and stacked. Step 3, One-time molding: Step 31, Mold Closure and Heating: Place the mold with the fiber-reinforced prepreg laid on it into the press for mold closure; Step 32, Resin Flow and Curing: Under pressure, the resin in the fiber-reinforced prepreg flows and fully fills every corner of the mold. At the same time, the resin undergoes a cross-linking reaction to achieve curing. Step 33, Pressure Holding: Maintain constant pressure during the curing process to ensure product dimensional stability and structural compactness; Step 4, Demolding and Post-processing: Step 41, CNC: After the mold is opened, the formed product is taken out of the mold cavity and the shape and structure are machined by CNC using a jig. Step 42, Cleaning: The CNC-machined product is put into an ultrasonic automatic cleaning line to clean the dirt off the product surface and obtain the fiber-reinforced composite material product.

2. The integral molding method for fiber-reinforced composite materials according to claim 1, characterized in that... In the fiber-reinforced prepreg, the matrix resin is one or a combination of two of thermoplastic resins and thermosetting resins; the fiber is one or more of carbon fiber, natural fiber, glass fiber, basalt fiber, and special fiber.

3. The integral molding method for fiber-reinforced composite materials according to claim 2, characterized in that... The thermoplastic resin is one or two of petroleum-based thermoplastic resin and bio-based thermoplastic resin, the thermosetting resin is one or two of petroleum-based thermosetting resin and bio-based thermosetting resin, and the special fiber is one or two of aramid fiber and ultra-high molecular weight polyethylene fiber.

4. The integral molding method for fiber-reinforced composite materials according to claim 2, characterized in that... The thermosetting resin is one or more of epoxy resin, polyimide resin, bismaleimide resin, unsaturated polyester, and vinyl resin, and the thermoplastic resin is one or more of PC, PP, PEEK, PA, PA6, and PA66.

5. The integral molding method for fiber-reinforced composite materials according to claim 1, characterized in that... The stacking method adopts a unidirectional ply stacking method with unidirectional ply stacking, and the ply directions are arranged in a cross pattern of 0°, ±45° or ±90°, with local areas reinforced by feature arrangement.

6. The integral molding method for fiber-reinforced composite materials according to claim 1, characterized in that... The temperature for one-time molding is 100~160℃, the pressure is 0.5~10MPa, and the holding time is 0.5~300min.

7. The integral molding method for fiber-reinforced composite materials according to claim 1, characterized in that... When the matrix resin is epoxy resin, a one-time compression molding process is used, with the temperature controlled at 100~160℃, the pressure at 0.5~10MPa, and the holding time at 3~60min. When the matrix resin is polyimide resin, a one-time compression molding process is used, with stepped heating, and the controlled temperatures are 180℃~250℃ and 250~300℃, the pressure at 0.5~10MPa, and the holding times at 10~40min and 30~120min, respectively. When the matrix resin is thermoplastic resin, a one-time hot pressing process is used, with the controlled temperature at 180~350℃, the molding time at 0.5~300min, and the molding pressure at 0.5~13MPa.

8. The method for integral molding of fiber-reinforced composite materials according to claim 1, characterized in that... The fiber-reinforced composite material product is one or more of the following: all-carbon fiber type, carbon fiber sandwich lightweight type, carbon fiber and glass fiber hybrid type, carbon fiber and glass fiber sandwich lightweight type, glass fiber type, or basalt fiber type.

9. The method for integral molding of fiber-reinforced composite materials according to claim 8, characterized in that... In the aforementioned lightweight sandwich type, the sandwich material is one or more of the following: PMI foam, PP plastic, POM foam, PU foam, PVC foam, carbon fiber porous felt, bamboo fiber porous felt, honeycomb PI core material, honeycomb PMI core material, and aramid honeycomb core material.

10. The integral molding method for fiber-reinforced composite materials according to claim 1, characterized in that... The surface of the fiber-reinforced composite material product has one or more carbon fiber weave textures selected from short-cut forging fine lines, short-cut forging coarse lines, woven textures, and UD straight lines. The woven texture is one or more selected from plain weave, twill weave, and satin weave.

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