Method and apparatus for warp compensation control of composite molding

Abstract

The application provides a kind of warping compensation control composite moulding forming method and device, comprising: based on fiber layer, product geometry, mould geometry and moulding forming process to establish digital twin model, calculate product warping size deviation and residual stress;In the model, add compensation soft diaphragm, control the forming pressure of different areas of product by designing the thickness of different areas of diaphragm, improve the size accuracy of product;The diaphragm of different thickness distribution of the optimization is laid on the surface of the preformed composite blank;The forming preform containing diaphragm is placed into the component forming mould, and after heating and pressurizing, it is cooled to integrally form composite component;Verify the component forming precision improvement effect, and feedback back to digital twin model.The application has the characteristics of easy control, low cost and quick modification, the soft diaphragm used not only can compensate the size accuracy of product, but also has the effect of easy demoulding, improving fiber body and surface quality.

Description

Technical Field

[0001] This invention relates to the field of advanced composite material manufacturing technology, and more specifically, to a method and apparatus for composite material compression molding with warp compensation control. Background Technology

[0002] As the demand for high-performance materials in advanced transportation equipment increases, the forming conditions of integrated die-cast aluminum alloys are stringent, and the material costs are constantly rising. In contrast, advanced composite materials, represented by glass fiber reinforced thermoplastic resin, are easy to form, have good performance, and their costs are constantly decreasing as production capacity increases. They are gradually being promoted and applied, and are the next generation of advanced structural materials.

[0003] Furthermore, unlike traditional hand-laid thermosetting composites, fiber-reinforced thermoplastic composite compression molding, through rapid additive layering and equal-material compression molding, is a low-cost, fast-paced, high-quality integrated material structure molding method. It represents the next generation of advanced composite molding technology for large-scale, standardized production, showing great potential in fields such as aerospace, automotive, and consumer electronics. However, due to the significant mismatch between the modulus and coefficient of thermal expansion of fibers and resins, molded products experience severe warping deformation during cooling after molding, seriously affecting dimensional accuracy. Excessive residual stress can even lead to component cracking, reducing yield and assembly quality. Traditional mold repair methods are time-consuming and costly, unable to meet the ever-increasing production pace requirements.

[0004] Therefore, when dealing with structural components with complex geometries, controlling residual stress and dimensional accuracy during the compression molding process of composite products is an urgent problem to be solved. The field still needs to propose more advanced and efficient composite material compression molding methods for warpage compensation control. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method and apparatus for molding composite materials with warp compensation control.

[0006] A method for molding composite materials with warp compensation control according to the present invention includes: Step S1: Establish a digital twin model based on fiber layup, product geometry, mold geometry, and compression molding process, and calculate product warpage dimensional deviation and residual stress; Step S2: Add a compensating soft film to the digital twin model, and control the molding pressure of different areas of the product by setting the thickness of different areas of the compensating soft film; Step S3: Form the optimized compensation soft film with different thickness distribution described in step S2, and lay it on the surface of the precast composite material blank; Step S4: Place the preform containing the compensating soft diaphragm described in step S3 into the component forming mold, heat and pressurize it, and then cool it to integrally form a composite material component. Step S5: Verify the improvement effect of the forming accuracy of the composite material component described in step S4, and feed the verification results back to the digital twin model in step S1 to optimize the model prediction accuracy or adjust the relevant structural parameters.

[0007] Preferably, the digital twin model in step S1 is a thermo-coupling simulation model; The thermo-coupling simulation model can describe the fiber angle change, high-temperature softening and interlayer sliding characteristics during the fiber prepreg molding process, and can be used to predict the residual stress distribution and warping deformation of the product. When establishing the digital twin model, the forming property parameters of each material must be accurately input.

[0008] Preferably, the mold geometry in step S1 is consistent with the actual mold geometry, and the product cavity thickness formed by the mold is greater than the actual product thickness, so as to provide space for placing the compensation soft film.

[0009] Preferably, the compensating soft diaphragm in step S2 has a large deformation capacity, and its material includes silicone, thermoplastic elastomer, thermoplastic rubber, polyurethane elastomer, olefin elastomer and thermoplastic dynamic vulcanized rubber. The maximum temperature resistance of the compensation soft diaphragm is higher than the product forming temperature.

[0010] Preferably, the molding method of the compensation soft diaphragm in step S3 includes injection molding, cutting, and 3D printing; In step S4, during the molding process, the mold temperature is lower than the temperature of the preform containing the compensating soft film, maintaining a medium-low temperature state. After the high-temperature preform is fed into the mold and quickly molded into a component, it is taken out and cooled.

[0011] A composite material compression molding apparatus for warp compensation control according to the present invention includes an upper mold, a lower mold, and a compensation soft diaphragm. The compensating soft diaphragm is laid on the surface of the precast composite material blank; The prefabricated composite material blank and the compensating soft diaphragm are placed together in the cavity formed by the upper mold and the lower mold; The thickness of the cavity is greater than the thickness of the actual product.

[0012] Preferably, the compensating soft diaphragm has a non-uniform thickness distribution structure, and the thickness of its different regions is designed according to the optimization results of the constructed digital twin model, which is used to control the molding pressure of different regions of the precast composite material blank.

[0013] Preferably, the surface roughness of the compensating soft film can be adjusted according to the actual product surface requirements, which include at least one of high gloss, matte, and textured finishes.

[0014] Preferably, the material of the compensating soft diaphragm includes silicone, thermoplastic elastomer, thermoplastic rubber, polyurethane elastomer, olefin elastomer, and thermoplastic dynamic vulcanized rubber, and its maximum temperature resistance is higher than the temperature of the composite material compression molding.

[0015] Preferably, the prefabricated composite material preform is a fiber-reinforced thermoplastic composite preform; Both the upper and lower molds are aluminum alloy molds, and their geometric structures are consistent with those of the molds used in actual production.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The warpage compensation control composite molding method proposed in this invention makes full use of the high-temperature softening characteristics of fiber-reinforced thermoplastic composites. It adopts a high-temperature resistant, deformable soft diaphragm and applies a controllable molding pressure field on the composite material based on a simple diaphragm thickness distribution design. Appropriate pressure is deployed in different areas to compensate for molding warpage and ensure high-quality molding accuracy.

[0017] 2. The soft diaphragm used in this invention is flexible and easily deformable, with low cost, and can be quickly modified or replaced, greatly reducing the time, material and labor costs associated with traditional metal mold repair; and because of its high elasticity, it will rebound after pressure is released and can be reused.

[0018] 3. Based on the digital twin technology of molding, this invention can scientifically and quantitatively predict the warping characteristics of the molding process and the mold repair method. Compared with the traditional "cooking-style" manual experience trial molding method, it has the characteristics of high efficiency, high quality and low cost. Attached Figure Description

[0019] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the composite material compression molding method for warp compensation control according to the present invention; Figure 2 This is a schematic diagram and test results of the composite material compression molding of carbon fiber reinforced thermoplastic composite B-pillar for warp compensation control according to the present invention.

[0020] In the attached drawings, the reference numerals are: 1-upper mold, 2-compensating soft diaphragm, 3-prefabricated composite material blank, and 4-lower mold. Detailed Implementation

[0021] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0022] According to the present invention, a method for molding composite materials with warp compensation control is provided, such as... Figure 1 As shown, it includes: Step S1: Establish a digital twin model based on fiber layup, product geometry, mold geometry, and compression molding process to calculate product warpage dimensional deviation and residual stress. The forming digital twin model in Step S1 is a thermo-mechanical coupling simulation, which can describe fiber angle changes, high-temperature softening, and interlayer sliding characteristics during fiber prepreg molding, effectively predicting the distribution of residual stress and warpage deformation in the product. The forming digital twin model can refer to patent application CN120412847A, and the forming property parameters of each material should be accurately input into the forming digital twin model. The mold geometry in Step S1 should be consistent with the actual mold structure geometry, and the thickness of the resulting product cavity needs to be greater than the actual product to provide space for inserting the soft diaphragm.

[0023] Step S2: Add a compensating soft diaphragm to the model described in Step S1. By designing the thickness of different areas of the diaphragm, the molding pressure in different areas of the product is controlled, thereby improving the dimensional accuracy of the product. The compensating soft diaphragm has a large deformation capacity, and its surface roughness can be adjusted according to the actual product surface requirements (including but not limited to high gloss, matte, and textured finishes). Materials include, but are not limited to, silicone rubber, thermoplastic elastomers, thermoplastic rubber, polyurethane elastomers, olefin elastomers, and thermoplastic dynamic vulcanized rubber. The maximum temperature resistance of the compensating soft diaphragm should be higher than the product molding temperature to prevent the diaphragm from melting and being damaged.

[0024] Step S3: Form the optimized film with different thickness distribution described in step S2 and lay it on the surface of the precast composite material blank; the forming methods for forming the optimized film with different thickness distribution in step S3 include, but are not limited to, injection molding, cutting, and 3D printing.

[0025] Step S4: Place the preform containing the diaphragm described in Step S3 into the component forming mold, heat and pressurize it, then cool it to integrally form a composite material component. During the forming process in Step S4, the mold temperature should be lower than the temperature of the preform containing the diaphragm, maintaining a medium-low temperature state. After the high-temperature preform is fed into the mold and rapidly formed into a component, it is removed and cooled.

[0026] Step S5: Verify the improvement effect of component forming accuracy described in Step S4, and feed it back to the digital twin model in Step S1. The digital twin model fed back to Step S1 can improve prediction accuracy or further optimize the layup structure and membrane structure based on the improvement effect of component forming accuracy.

[0027] Furthermore, the specific description of the present invention in conjunction with practical application scenarios is as follows: This embodiment provides a warp-compensated composite material compression molding process for carbon fiber reinforced thermoplastic composite flat tensile specimens, comprising: an upper aluminum alloy mold, high-temperature resistant silicone, a carbon fiber reinforced thermoplastic composite preform, and a lower aluminum alloy mold. The specific molding steps are as follows: T1: T700 unidirectional carbon fiber reinforced polypropylene thermoplastic prepreg with a single layer thickness of 0.1 mm is cut and laid into flat stretched strips, and 20 layers are symmetrically laid at a helical angle of 9° to form a helical layup structure (layup [0° / 9° / 18° / … / 171°)). s (Dimensions: 250*15*2mm)

[0028] T2: Add silicone to the preform sheet described in T1. The silicone is designed according to the molding simulation to have a thickness distribution structure that is thicker around the edges and thinner in the center, with an edge thickness of 3mm and a center thickness of 2mm.

[0029] T3: Place the preform containing the diaphragm described in T2 into the component forming mold, heat the material to 200°C, and the mold temperature is 150°C. After forming, allow it to cool in the air to form a composite material flat stretching strip.

[0030] T4: Demold and remove the composite material flat plate tensile specimen described in T3, test the warpage deformation based on a three-coordinate measuring machine, and perform a tensile test.

[0031] The maximum warpage deformation of the composite flat plate tensile specimen with warpage compensation control was 0.273 mm, which is 52.49 times higher than that of the uncompensated tensile specimen (maximum warpage deformation was 14.331 mm). The tensile modulus was 43.2 GPa and the tensile strength was 397.1 MPa.

[0032] Furthermore, a composite material compression molding process for a carbon fiber reinforced thermoplastic composite B-pillar engineering component for a car body, with warp compensation control, is provided. The component includes: an upper aluminum alloy mold, high-temperature resistant silicone, a carbon fiber reinforced thermoplastic composite preform, and a lower aluminum alloy mold. The specific molding steps are as follows: T1: T700 unidirectional carbon fiber reinforced polypropylene thermoplastic prepreg with a single layer thickness of 0.1 mm is cut and laid into flat stretched strips, and 20 layers are symmetrically laid at a helical angle of 9° to form a helical layup structure (layup [0° / 9° / 18° / … / 171°)). s(Dimensions: 600*500*2mm)

[0033] T2: Add silicone to the preform sheet described in T1. The silicone is designed according to the molding simulation to have a thickness distribution structure that is thicker around the edges and thinner in the center, with an edge thickness of 5mm and a center thickness of 2mm.

[0034] T3: Place the preform containing the film described in T2 into the component forming mold, heat the material to 200°C, the mold temperature is 150°C, and allow it to cool in the air after forming to form a composite material flat stretching strip. T4: Demold and remove the composite material B-pillar component of the vehicle body described in T3, test the warping deformation based on a three-coordinate testing system, and perform a three-point bend test.

[0035] The schematic diagram and test results of the complex engineering parts are as follows: Figure 2 As shown, the maximum warpage deformation of the obtained composite material engineering part is 0.916 mm, which is 40.7 times higher than the dimensional accuracy of the uncompensated component (the maximum warpage deformation is 37.284 mm), and the cost is reduced by 20 times compared with the traditional mold repair method (the cost of the silicone diaphragm used in this embodiment is 100 yuan, while the traditional mold repair costs 2,000 yuan and takes more than 3 weeks). The failure load of the three-point bend is 7585.6 N.

[0036] According to the present invention, a composite material compression molding apparatus for warpage compensation control includes: an upper mold, a lower mold, and a compensating soft diaphragm. The compensating soft diaphragm is laid on the surface of a preformed composite material blank (e.g., a carbon fiber reinforced thermoplastic composite preform). The preformed composite material blank and the compensating soft diaphragm are placed together in a cavity formed by the upper and lower molds, and the cavity thickness is greater than the actual product thickness. The compensating soft diaphragm has a non-uniform thickness distribution structure, and the thickness of its different regions is designed according to the optimization results of a constructed digital twin model, used to control the molding pressure of different regions of the preformed composite material blank. The surface roughness of the compensating soft diaphragm can be adjusted according to the actual product surface requirements, which include at least one of high gloss, matte, and textured finishes. The material of the compensating soft diaphragm includes silicone, thermoplastic elastomers, thermoplastic rubber, polyurethane elastomers, olefin elastomers, and thermoplastic dynamic vulcanized rubber, and its maximum temperature resistance is higher than the temperature of composite material compression molding. The precast composite material blank is a fiber-reinforced thermoplastic composite preform; both the upper and lower molds are aluminum alloy molds, and the mold geometry is consistent with the actual production mold geometry.

[0037] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0038] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for compression molding of composite materials with warp compensation control, characterized in that, include: Step S1: Establish a digital twin model based on fiber layup, product geometry, mold geometry, and compression molding process, and calculate product warpage dimensional deviation and residual stress; Step S2: Add a compensating soft film to the digital twin model, and control the molding pressure of different areas of the product by setting the thickness of different areas of the compensating soft film; Step S3: Form the optimized compensation soft film with different thickness distribution described in step S2, and lay it on the surface of the precast composite material blank; Step S4: Place the preform containing the compensating soft diaphragm described in step S3 into the component forming mold, heat and pressurize it, and then cool it to integrally form a composite material component. Step S5: Verify the improvement effect of the forming accuracy of the composite material component described in step S4, and feed the verification results back to the digital twin model in step S1 to optimize the model prediction accuracy or adjust the relevant structural parameters.

2. The composite material compression molding method for warpage compensation control according to claim 1, characterized in that, The digital twin model mentioned in step S1 is a thermo-coupling simulation model; The thermo-coupling simulation model can describe the fiber angle change, high-temperature softening and interlayer sliding characteristics during the fiber prepreg molding process, and can be used to predict the residual stress distribution and warping deformation of the product. When establishing the digital twin model, the forming property parameters of each material need to be input.

3. The composite material compression molding method for warpage compensation control according to claim 1, characterized in that, The mold geometry described in step S1 is consistent with the actual mold geometry, and the product cavity thickness formed by the mold is greater than the actual product thickness, which is used to provide space for placing the compensation soft film.

4. The composite material compression molding method for warpage compensation control according to claim 1, characterized in that, The compensating soft diaphragm described in step S2 has a large deformation capacity, and its materials include silicone, thermoplastic elastomer, thermoplastic rubber, polyurethane elastomer, olefin elastomer and thermoplastic dynamic vulcanized rubber. The maximum temperature resistance of the compensation soft diaphragm is higher than the product forming temperature.

5. The composite material compression molding method for warpage compensation control according to claim 1, characterized in that, The molding method for the compensation soft diaphragm in step S3 includes injection molding, cutting, and 3D printing; In step S4, during the molding process, the mold temperature is lower than the temperature of the preform containing the compensating soft film, maintaining a medium-low temperature state. After the high-temperature preform is fed into the mold and quickly molded into a component, it is taken out and cooled.

6. A composite material compression molding apparatus for warp compensation control, characterized in that, This includes the upper mold, the lower mold, and the compensating soft film; The compensating soft diaphragm is laid on the surface of the precast composite material blank; The prefabricated composite material blank and the compensating soft diaphragm are placed together in the cavity formed by the upper mold and the lower mold; The thickness of the cavity is greater than the thickness of the actual product.

7. The composite material compression molding apparatus for warpage compensation control according to claim 6, characterized in that, The compensating soft diaphragm has a non-uniform thickness distribution structure. The thickness of its different regions is designed based on the optimization results of the constructed digital twin model, and is used to control the molding pressure of different regions of the precast composite material blank.

8. The composite material compression molding apparatus for warpage compensation control according to claim 6, characterized in that, The surface roughness of the compensation soft film can be adjusted according to the actual product surface requirements, which include at least one of high gloss, matte, and leather texture.

9. The composite material compression molding apparatus for warpage compensation control according to claim 6, characterized in that, The materials of the compensation soft diaphragm include silicone, thermoplastic elastomer, thermoplastic rubber, polyurethane elastomer, olefin elastomer, and thermoplastic dynamic vulcanized rubber, and its maximum temperature resistance is higher than that of the composite material compression molding temperature.

10. The composite material molding apparatus for warpage compensation control according to claim 6, characterized in that, The prefabricated composite material blank is a fiber-reinforced thermoplastic composite preform; Both the upper and lower molds are aluminum alloy molds, and their geometric structures are consistent with those of the molds used in actual production.

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