Forming technique of anisotropic hollow polymer fiber reinforced composite based on phase change material

Abstract

The application belongs to the field of polymer and discloses a forming technology of anisotropic cavity polymer fiber reinforced composite based on phase change material. First, a phase change material is selected as a material for preparing an inner mold, and the phase change material is cast or carved into a sample shape; PVA and glycerol are dissolved in water to prepare a barrier agent, which is coated on the inner mold; glass fiber or carbon fiber prepreg and other forming materials are covered on the coated inner mold; a corresponding outer mold with flanges which can be separated up and down is prepared by turning or carving technology; the combination of the fiber prepreg and the inner mold is placed in the outer mold, and pressure is applied to the flanges in the up and down directions to play the role of external fixation. The inner mold, the forming material and the outer mold are assembled and placed in an oven, and heating is performed to solidify the fiber prepreg into a shape. After shaping, the outer mold is removed, heating is performed to a temperature above the phase change temperature of the phase change material, the inner mold becomes a flow state, flows out from the product opening, and finally the shaped product is obtained. The forming technology has the advantages of simple process, easy demolding and high recycling of the phase change material, and the technology is easy to realize industrialization.

Description

Technical Field

[0001] This invention relates to the molding technology of heterogeneous hollow fiber-reinforced polymer composite materials based on phase change materials. The key feature is the use of phase change materials to prepare the inner mold and the use of glycerol-plasticized PVA as a barrier layer to reduce the contamination of the molded product by materials such as phase change paraffin wax, thereby affecting the mechanical properties of the product. Background Technology

[0002] As high-end equipment such as drones and robots develop towards higher mobility and longer endurance, stringent requirements are placed on the lightweighting and high strength of their airframe structures. To eliminate the weight and stress concentration of connectors resulting from the traditional "skeleton + skin" assembly method, integrated molding technology has gradually become mainstream, giving rise to a large number of irregularly shaped structural components with complex internal cavities. Fiber-reinforced polymer composites, with their excellent specific strength and designability, have become ideal materials for manufacturing these irregularly shaped cavity components. However, the difficulty in molding these irregularly shaped cavity structures is a technological bottleneck restricting their large-scale application.

[0003] Currently, the most widely used molding technologies in the polymer materials industry mainly include injection molding, extrusion molding, blow molding, and compression molding. Among them, injection molding is highly efficient but the mold cost is expensive and it is prone to defects such as shrinkage cavities and warping; extrusion molding can only produce profiles with uniform cross-sections and cannot process complex three-dimensional structures; blow molding has difficulty controlling the uniformity of wall thickness in complex cavities; traditional compression molding is suitable for composite materials, but it is difficult to form closed irregular-shaped components with undercuts or complex internal flow channels. Therefore, the above conventional methods cannot meet the requirements for efficient and high-quality manufacturing of fiber-reinforced composite irregular-shaped cavity components.

[0004] For the molding of irregular cavities in fiber-reinforced composite materials, the industry currently mainly adopts a technical solution combining composite material molding processes (such as vacuum-assisted resin transfer molding) with multi-lobed rigid internal molds. This solution involves dividing a metal or hard mold into multiple segments, which are then sequentially removed from the narrow opening after the component has cured, thus achieving the internal cavity molding. However, multi-lobed internal molds suffer from three major pain points that are difficult to overcome in practical applications: (1) Complex structure and high cost: Multi-part molds require precise guiding, positioning and locking mechanisms, have a long design cycle and require extremely high machining accuracy, resulting in a single-piece manufacturing cost that is much higher than that of the overall mold. (2) Limited applicability: When the opening of the product is too small or the inner cavity is extremely irregular (such as deep cavity, large curvature bend), the petal block often cannot be removed smoothly, which can easily cause the product to be scrapped; (3) Poor molding accuracy: There will inevitably be seams at the splicing of multiple parts, which not only affects the smoothness of the inner surface of the product, but also easily produces flash or springback during high temperature and high pressure molding, making it difficult to guarantee a high-precision aerodynamic shape.

[0005] To address the aforementioned technical deficiencies, this invention proposes a molding technology for heterogeneous hollow polymer fiber-reinforced composite materials based on phase change materials. The high rigidity of the phase change material at room temperature serves as an inner mold, and upon heating to the phase change temperature, it automatically liquefies and flows out from the product opening. This replaces the traditional segmented rigid inner mold, aiming to solve the industry problems of difficult demolding and complex processes for irregularly shaped, small-opening hollow composite material components. Summary of the Invention

[0006] This invention addresses the shortcomings of existing fiber-reinforced composite irregular cavity component molding technologies, such as difficulties in demolding, complex processes, and limited applicability to small openings or fully enclosed structures. It discloses a molding method for irregular cavity polymer fiber-reinforced composite materials based on phase change materials.

[0007] In response to the urgent need for lightweight, high-strength, integrated irregular cavity structural components in fields such as aerospace, drones, and robotics, and considering the limitations of existing polymer molding technologies (such as injection molding, extrusion, blow molding, and compression molding) and multi-lobed combined internal mold methods in the molding of complex internal cavities, this invention proposes a molding method for irregular cavity composite materials using phase change materials as internal molds, fiber-reinforced epoxy resin prepregs as molding materials, and a separable external mold.

[0008] A method for molding heterogeneous cavity polymer fiber-reinforced composite materials based on phase change materials includes the following steps, such as... Figure 1 As shown: (1) Provide an inner mold, which is made of a solid-liquid phase change material and whose shape corresponds to the internal shape of the irregular cavity of the target component; (2) A barrier layer is formed on the outer surface of the inner mold; (3) Use aluminum alloy engraving or epoxy resin molding technology to prepare an outer mold with separate upper and lower flanges; That is, the outer mold is a split structure consisting of at least two detachable modules, and adjacent modules are connected by a fastening structure.

[0009] (4) Apply the prepreg to the surface of the inner mold with the barrier layer, then place it in the outer mold, and tighten the flange to make the outer mold, the prepreg and the inner mold fit together tightly to constrain the molding and obtain the preform. (5) The preform is heated and cured under the first temperature condition to form a composite material part; (6) Remove the outer mold; (7) The composite material part and the inner mold are heated together to a second temperature, causing the inner mold to undergo a solid-liquid phase change and become a flowable substance. This flowable substance is discharged from the opening of the composite material part, thereby obtaining a composite material component with the irregular cavity. Some irregular structures are as follows: Figure 2 As shown.

[0010] The phase change material used to prepare the inner mold includes one or more combinations of paraffin wax, fatty acids, inorganic hydrated salts, and organic sugar alcohols; the solid-liquid phase change material contains thermally conductive fillers. The phase change temperature range is 10–180°C.

[0011] The internal mold forming methods include casting, carving, and 3D printing technology.

[0012] The fatty acid is selected from any one or a combination of acetic acid, decanoic acid, lauric acid, pentadecanoic acid, myristic acid, and palmitic acid.

[0013] The inorganic hydrated salt is selected from any one or a combination of CaCl2·6H2O, Na2SO4·10H2O, Na2HPO4·12H2O, CH3COONa·3H2O, Na2HPO4·12H2O, CH3COONa·3H2O, Ba(OH)2·8H2O, and MgCl2·6H2O.

[0014] The organic sugar alcohol is selected from any one or a combination of xylitol, erythritol, and D-mannitol.

[0015] The above-mentioned paraffin wax (phase transition temperature range 10–70℃); fatty acids such as acetic acid CH3COOH (melting point 16.7℃), decanoic acid CH3(CH2)8COOH (melting point 36℃), and lauric acid CH3(CH2) 10 COOH, with a melting point of 49℃, is n-pentadecanoic acid (CH3(CH2)). 13 COOH, with a melting point of 52.5℃, myristic acid CH3(CH2) 12 COOH, with a melting point of 58℃, palmitic acid CH3(CH2) 14 COOH has a melting point of 65.1℃; inorganic hydrated salts such as CaCl2·6H2O have a melting point of 30℃, Na2SO4·10H2O has a melting point of 32.4℃, Na2HPO4·12H2O has a melting point of 35.5℃, CH3COONa·3H2O has a melting point of 58℃, Ba(OH)2·8H2O has a melting point of 78℃, and MgCl2·6H2O has a melting point of 116.7℃; organic sugar alcohols such as xylitol (C5H) 12 O5, with a phase transition temperature of 94.3℃, erythritol C4H 10O4, with a melting point of 120℃, D-mannitol (C6H) 14 O6, one of which has a melting point of 166-168℃.

[0016] The thermally conductive filler is selected from one or more combinations of graphite, carbon nanotubes, graphene, and metal powder.

[0017] The barrier layer is formed by coating and drying an aqueous composition of a film-forming substance and a plasticizer; the film-forming substance is polyvinyl alcohol and the plasticizer is glycerin.

[0018] The external mold preparation technology includes epoxy resin molding technology, aluminum alloy engraving technology, etc.

[0019] In the aqueous composition, the mass ratio of polyvinyl alcohol, glycerin and water is (1-10):(0.5-5):100, and the thickness of the barrier layer formed is 0.01-2 mm.

[0020] In some preferred cases, a barrier agent is prepared by mixing PVA, glycerin and water in a mass ratio of 5:1:94 and applied to the surface of the inner mold to prevent the phase change material in the inner mold from penetrating into the prepreg layer.

[0021] The prepreg material described in step (4) comprises reinforcing fibers and matrix resin, wherein the reinforcing fibers are one or more of carbon fiber, glass fiber, and aramid fiber; and the matrix resin is epoxy resin.

[0022] In step (5), the first temperature is lower than the phase transition temperature of the solid-liquid phase change material.

[0023] In step (6), the second temperature is higher than the phase transition temperature of the solid-liquid phase change material.

[0024] In step (7), the irregular cavity has at least one opening, the size of which is not limited, and the irregular cavity polymer fiber reinforced composite material product can be a very small opening or an approximately closed structure.

[0025] The steps also include collecting the discharged liquid solid-liquid phase change material, cooling and recycling it for remanufacturing the inner mold.

[0026] Specifically, unmodified epoxy resin exhibits high brittleness and poor impact resistance after curing, making it difficult to meet the safety requirements of high-end equipment. Therefore, this invention uses fiber-reinforced epoxy resin (such as glass fiber and carbon fiber) as the molding material, significantly improving its strength and fatigue resistance. However, for irregularly shaped structural parts with complex internal cavities, such as spherical, ellipsoidal, and biomimetic streamlined parts, traditional rigid inner molds cannot be easily removed after curing. To address this, this invention introduces phase change materials to prepare the inner mold, and preferably adds thermally conductive fillers such as graphite to improve its thermal conductivity, ensuring that the inner mold can undergo a rapid and uniform solid-liquid phase change during the demolding stage, thereby achieving complete removal from the inside of the product.

[0027] Specifically, in the technical solution of this application, taking paraffin-based phase change materials as an example, the typical implementation process of this invention is as follows: First, paraffin wax is mixed with an appropriate amount of graphite and melted, and then prepared into the required irregular-shaped inner mold by casting, 3D printing, carving, or other methods; second, polyvinyl alcohol (PVA), glycerin, and water are mixed in a certain proportion to prepare a barrier agent, which is then uniformly coated on the surface of the inner mold to form a dense barrier layer, preventing the phase change material from penetrating into the fiber reinforcement layer during the subsequent curing process; then, fiber-reinforced epoxy resin prepreg is covered on the outer surface of the barrier layer to form the product layer; then... The outer mold, which can be separated into upper and lower parts and has a flange, is prepared by using techniques such as aluminum alloy engraving or epoxy resin molding. The inner mold, prepreg, and outer mold are assembled and fastened to ensure that the three fit together tightly. Then, the whole thing is placed in an oven and the epoxy resin is fully cured and shaped at a set curing temperature (lower than the phase change temperature of the phase change material). Finally, the outer mold is removed, and the cured product layer and the inner mold are heated to above the melting point of the phase change material, so that the inner mold is completely liquefied and flows out along the product opening, finally obtaining a complete irregular cavity composite material product that has been completely removed from the inner mold.

[0028] The products prepared by this technology have advantages such as high strength, fatigue resistance, and clean inner surface. The process is simple, demolding does not require mechanical disassembly, and the phase change material can be recycled and reused, which has excellent circular economy and industrialization prospects.

[0029] The present invention has the following significant advantages over the prior art: This molding technology utilizes phase change materials to prepare the inner mold. Below the phase change temperature, it possesses the strength to serve as the inner mold, while above the phase change temperature, it transforms into a fluid dynamic, allowing it to flow out through very small openings. Based on this principle, it is possible to manufacture components with very small openings, almost completely enclosed, and is particularly suitable for manufacturing irregularly shaped components with multiple curves or cross-sections that change along the component's axis.

[0030] Phase change materials have good plasticity and can be used to prepare inner membranes of different shapes through carving, casting and 3D printing.

[0031] Compared with traditional segmented rigid inner molds, this invention does not require complex guiding, positioning and opening / closing mechanisms. The inner mold can be removed by melting, which greatly simplifies the mold structure and molding process.

[0032] This invention uses phase change materials to prepare the inner mold. Compared with traditional molding technology, phase change materials can be recycled, which effectively improves resource utilization.

[0033] This molding technology, by adding thermally conductive materials, can achieve uniform heat transfer to the inner mold, avoiding the problem of the inner mold being unable to be removed due to uneven heating.

[0034] The PVA / glycerin barrier layer coated on the surface of the inner mold can effectively prevent the phase change material from penetrating or contacting the fiber reinforcement layer during the curing or melting process, thereby avoiding product contamination and ensuring internal quality and surface quality. Attached Figure Description

[0035] Figure 1 : Experimental flowchart of the molding technology of irregular cavity fiber-reinforced composite material based on paraffin phase change material described in Embodiment 1 of the present invention.

[0036] Figure 2 : Schematic diagrams of the four irregular cavity structures involved in this invention.

[0037] Figure 3 : A physical image of the product in Embodiment 1 of the present invention.

[0038] Figure 4 : A physical image of the exported product in Embodiment 1 of the present invention. Detailed Implementation

[0039] The present invention will be further illustrated below with reference to specific embodiments. However, these embodiments are only for further explanation of the present invention and are not intended to limit the scope of the present invention. The specific curing temperatures and selection of phase change materials involved in the specific embodiments are listed in these specific embodiments for the purpose of illustrating the present invention and are not intended to limit the present invention in any way.

[0040] Example 1 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 6615 g of paraffin wax, heat it to melt, and then add approximately 330 g of graphite and stir evenly; while still hot, pour the paraffin / graphite mixture into a cylindrical container to cool and solidify as the inner mold material. Use a carving machine to carve the paraffin / graphite mixture into a spherical inner mold that conforms to the product; PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0041] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0042] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0043] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has cured. The product is cut using a high-pressure water gun to form a product outlet with a diameter of 0.5cm. The product layer and the inner paraffin mold are placed in an oven and heated to about 60℃. The paraffin mold melts and flows out along the product outlet until it is completely drained, resulting in the final product.

[0044] Example 2 Preparation of the inner mold: Taking the preparation of a spherical hollow product with a diameter of 20 cm as an example, 6419 g of lauric acid (CH3(CH2)) was weighed. 10 (COOH), melt it, add 321 g of graphite, and while hot, pour the lauric acid / graphite mixture into a cylindrical container to cool and solidify as the inner mold material. Use a carving machine to carve the lauric acid / graphite mixture into a spherical inner mold that matches the product.

[0045] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0046] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0047] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the lauric acid phase transition temperature.

[0048] Demolding: After the product layer has cured, remove the outer mold. Use a high-pressure water gun to cut the product to form a product outlet with a diameter of 0.5cm. Place the product layer and the inner lauric acid mold in an oven and heat to about 55°C. The lauric acid material melts and flows out along the product outlet to obtain the product.

[0049] Example 3 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, 12430 g of CaCl2·6H2O was weighed, melted, and 622 g of graphite was added. While still hot, the calcium chloride hexahydrate / graphite mixture was poured into a cylindrical container to cool and solidify, serving as the material for the inner mold. The calcium chloride hexahydrate / graphite mixture was then sculpted into a spherical inner mold conforming to the product using a carving machine. The CaCl2·6H2O mixture was then sculpted into a spherical inner mold conforming to the product using a carving machine.

[0050] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0051] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0052] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the phase transition temperature of CaCl3·6H2O.

[0053] Demolding: After the product layer has cured, remove the outer mold. Use a high-pressure water gun to cut and form the product outlet, with an outlet diameter of 0.5mm. Place the product layer and the inner CaCl2·6H2O / graphite inner mold in an oven and heat to about 40℃. The CaCl2·6H2O will become fluid and flow out along the product outlet.

[0054] Example 4 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, 11050 g of xylitol (C5H) was weighed. 12 After melting O5, add 552 g of graphite. While still hot, pour the xylitol / graphite mixture into a cylindrical container to cool and solidify, using it as the inner mold material. Use a carving machine to carve the xylitol / graphite mixture into a spherical inner mold that matches the product.

[0055] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0056] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. First, the epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is then removed and placed on top of the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and secured.

[0057] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the xylitol phase transition temperature.

[0058] Demolding: After the product layer has cured, remove the outer mold. Use a high-pressure water gun to cut the product to form the product outlet, with an outlet diameter of 0.5cm. Place the product layer and the inner xylitol / graphite mold in an oven and heat to about 103℃. The xylitol material melts and flows out along the product outlet to obtain the product.

[0059] Example 5 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, 3650 g of paraffin wax is weighed as a phase change material, melted and then 182 g of graphite is added. The paraffin wax / graphite is then cast into a spherical inner mold that matches the product using casting technology.

[0060] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0061] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0062] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0063] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has cured. The product is cut using a high-pressure water gun to form a product outlet with a diameter of 0.5cm. The product layer and the inner paraffin mold are placed in an oven and heated to about 60℃. The paraffin mold melts and flows out along the product outlet until it is completely drained, resulting in the final product.

[0064] Example 6 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, 3650 g of paraffin wax is weighed as a phase change material, melted and then 182 g of graphite is added. The paraffin wax / graphite is then cast into a spherical inner mold that matches the product using casting technology.

[0065] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0066] Product manufacturing: An epidural mold with an inner diameter of 20 cm and separable upper and lower parts is prepared. The epidural / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. After the total diameter of the 0.5 cm thick product layer and the 19 cm diameter inner mold reaches 20 cm, an epidural mold with an inner diameter of 20 cm and separable upper and lower parts is prepared and fixed using the epidural mold.

[0067] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0068] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has solidified. The product layer is cut using a high-pressure water gun to form a product outlet with a diameter of 0.5cm. The product layer and the inner paraffin mold are placed in an oven and heated to about 60℃. The paraffin mold melts and flows out along the product outlet until all of it has flowed out, resulting in the final product.

[0069] Example 7 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, 3650 g of paraffin wax is weighed as a phase change material, melted and added to graphite, and then the paraffin wax / graphite is printed into a spherical inner mold that matches the product using 3D printing technology.

[0070] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0071] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0072] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0073] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has solidified. The product layer is cut using a high-pressure water gun to form the product outlet, with an outlet diameter of 0.5cm. The product layer and the inner paraffin mold are placed in an oven and heated to about 60℃. The paraffin mold melts and flows out along the product outlet until all the product has flowed out, resulting in the final product.

[0074] Example 8 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 3453g of cinnammic acid and 1943g of palmitic acid, heat them to melt, and then add approximately 269.8g of graphite and stir evenly. While still hot, pour the palmitic acid / cinnammic acid / graphite mixture into a cylindrical container to cool and solidify as the inner mold material. Use a carving machine to carve the palmitic acid / cinnammic acid graphite mixture into a spherical inner mold that conforms to the product.

[0075] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0076] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0077] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the phase transition temperature of the palmitic acid / cinnamic acid mixture.

[0078] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has solidified. A high-pressure water gun is used to cut the product layer to form the product outlet, with an outlet diameter of 0.5cm. The product layer and the inner palmitic acid / cinnamic acid mold are placed in an oven and heated to approximately 50°C. The palmitic acid / cinnamic acid inner mold melts and flows out along the product outlet until all the product has flowed out, yielding the final product.

[0079] Example 9 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 7298g of xylitol and 1917g of erythritol, heat them to melt, and then add approximately 461g of graphite and stir evenly. While still hot, pour the xylitol / erythritol / graphite mixture into a cylindrical container to cool and solidify, which will serve as the material for the inner mold. Use a carving machine to carve the xylitol / erythritol / graphite mixture into a spherical inner mold that matches the product.

[0080] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0081] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0082] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the melting point of xylitol / erythritol.

[0083] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has solidified. The product layer is cut using a high-pressure water gun to form the product outlet, with an outlet diameter of 0.5cm. The product layer and the inner mold are placed in an oven and heated to about 90℃. The xylitol / erythritol inner mold melts and flows out along the product outlet until all the product has flowed out, resulting in the final product.

[0084] Example 10 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 6615 g of paraffin wax, heat it to melt, and then add approximately 463.05 g of copper powder and stir evenly; while still hot, pour the paraffin wax / copper powder mixture into a cylindrical container to cool and solidify as the inner mold material. Use a carving machine to carve the paraffin wax / copper powder mixture into a spherical inner mold that matches the product; PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0085] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0086] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0087] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has cured. The product is cut using a high-pressure water gun to form a product outlet with a diameter of 0.5cm. The product layer and the inner paraffin mold are placed in an oven and heated to about 60℃. The paraffin mold melts and flows out along the product outlet until it is completely drained, resulting in the final product.

[0088] Example 11 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 6615 g of paraffin wax, heat it to melt, and then add approximately 416.7 g of carbon nanotubes and stir evenly; while still hot, pour the paraffin wax / carbon nanotube mixture into a cylindrical container to cool and solidify as the inner mold material. Use a carving machine to carve the paraffin wax / carbon nanotube mixture into a spherical inner mold that matches the product.

[0089] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0090] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0091] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0092] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has cured. The product is cut using a high-pressure water gun to form a product outlet with a diameter of 0.5cm. The product layer and the inner paraffin mold are placed in an oven and heated to about 60℃. The paraffin mold melts and flows out along the product outlet until it is completely drained, resulting in the final product.

[0093] Example 12 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 6615 g of paraffin wax, heat it to melt, and then add approximately 416.7 g of a mixture of graphite and copper powder in equal proportions and stir evenly. While still hot, pour the paraffin / graphite / copper powder mixture into a cylindrical container to cool and solidify, thus using it as the material for the inner mold. Use a carving machine to carve the paraffin / graphite / copper powder mixture into a spherical inner mold that matches the product.

[0094] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0095] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0096] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0097] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has cured. The product is cut using a high-pressure water gun to form a product outlet with a diameter of 0.5cm. The product layer and the inner paraffin mold are placed in an oven and heated to about 60℃. The paraffin mold melts and flows out along the product outlet until it is completely drained, resulting in the final product.

[0098] Example 13 Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 6615 g of paraffin wax, heat it to melt, and then add approximately 330 g of graphite and stir evenly; while still hot, pour the paraffin / graphite mixture into a cylindrical container to cool and solidify as the inner mold material. Use a carving machine to carve the paraffin / graphite mixture into a spherical inner mold that conforms to the product; PVA, glycerin and water are mixed in a mass ratio of 1:4:95 to form a barrier agent. The prepared barrier agent is then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.3 mm.

[0099] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0100] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0101] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has cured. The product is cut using a high-pressure water gun to form a product outlet with a diameter of 0.5cm. The product layer and the inner paraffin mold are placed in an oven and heated to about 60℃. The paraffin mold melts and flows out along the product outlet until it is completely drained, resulting in the final product.

[0102] Example 14 Fiber Changes Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 6615 g of paraffin wax, heat it to melt, and then add approximately 330 g of graphite and stir evenly; while still hot, pour the paraffin / graphite mixture into a cylindrical container to cool and solidify as the inner mold material. Use a carving machine to carve the paraffin / graphite mixture into a spherical inner mold that conforms to the product.

[0103] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0104] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / glass fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0105] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0106] Demolding: The outer mold has a separable structure, and the outer mold is removed after the product layer has cured. The product is cut using a high-pressure water gun to form a product outlet with a diameter of 0.5cm. The product layer and the inner paraffin mold are placed in an oven and heated to about 60℃. The paraffin mold melts and flows out along the product outlet until it is completely drained, resulting in the final product.

[0107] Example 15 (Control group without barrier layer) Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 6615 g of paraffin wax, heat it to melt, and then add approximately 330 g of graphite and stir evenly; while still hot, pour the paraffin / graphite mixture into a cylindrical container to cool and solidify as the inner mold material. Use a carving machine to carve the paraffin / graphite mixture into a spherical inner mold that conforms to the product.

[0108] No barrier layer is prepared.

[0109] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0110] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0111] Demolding: The outer mold has a separable structure. After the product layer has cured, the outer mold is removed. The product layer and the inner paraffin mold are placed in an oven and heated to about 60°C. After the inner paraffin mold melts, it flows out along the product outlet. The product outlet is formed by cutting with a high-pressure water gun until all the product flows out, resulting in the final product.

[0112] The product layer surface is sticky because the phase change material used to prepare the inner mold has seeped into the product layer during the production process, contaminating the product layer.

[0113] Example 16 (Control group without thermally conductive material) Preparation of the inner mold: Taking the preparation of a spherical cavity product with a diameter of 20 cm as an example, weigh approximately 6615 g of paraffin wax, heat it to melt without adding heat-conducting materials; while still hot, pour the paraffin wax into a cylindrical container to cool and solidify as the material for the inner mold. Use a carving machine to carve the paraffin / graphite mixture into a spherical inner mold that matches the product.

[0114] PVA, glycerin and water were mixed in a mass ratio of 1:5:94 to form a barrier agent. The prepared barrier agent was then evenly coated onto the surface of the inner mold to form a barrier layer with a thickness of about 0.2 mm.

[0115] Product manufacturing: An outer mold with an inner diameter of 20 cm is prepared using aluminum alloy engraving technology. The epoxy resin / carbon fiber prepreg is cooled to 5°C to inhibit its reaction rate. The prepreg is removed and applied to the inner mold to form a 0.5 cm thick product layer. The total diameter of the 0.5 cm thick product layer combined with the 19 cm diameter inner mold reaches 20 cm. A separable outer mold is used and fixed in place.

[0116] The entire assembly, including the inner mold, prepreg, and outer mold, is placed in an oven for curing. The curing temperature is set to be 10°C lower than the paraffin phase transition temperature.

[0117] Demolding: The outer mold has a separable structure. After the product layer has cured, the outer mold is removed. The product layer and the inner paraffin mold are placed in an oven and heated to about 60°C. The paraffin mold melts and flows out along the product outlet until it is completely discharged, resulting in the final product.

[0118] During the demolding process, due to uneven heating, the phase change material near the product layer melts first, while the phase change material in the center remains solid. This results in a demolding time that is much longer than that of cases with added thermally conductive materials. Additionally, there is residual phase change material.

[0119] Table 1: Summary of Phase Change Material Types, Inner Mold Molding Methods, Outer Mold Preparation Methods, Demolding Temperatures, and Product Molding Results Used in Examples 1-7 of the Present Invention .

Claims

1. A method for molding heterogeneous hollow polymer fiber-reinforced composite materials based on phase change materials, characterized in that, Includes the following steps: (1) Provide an inner mold, which is made of a solid-liquid phase change material and whose shape corresponds to the internal shape of the irregular cavity of the target component; (2) A barrier layer is formed on the outer surface of the inner mold; (3) Use aluminum alloy engraving or epoxy resin molding technology to prepare an outer mold with separate upper and lower flanges; (4) Apply the prepreg to the surface of the inner mold with the barrier layer, then place it in the outer mold, and tighten the flange to make the outer mold, the prepreg and the inner mold fit together tightly to constrain the molding and obtain the preform. (5) The preform is heated and cured under the first temperature condition to form a composite material part; (6) Remove the outer mold; (7) The composite material part and the inner mold are heated together to a second temperature, so that the inner mold undergoes a solid-liquid phase change and becomes a flowable substance. The flowable substance is discharged from the opening of the composite material part, thereby obtaining a composite material component with the irregular cavity.

2. The molding method for heterogeneous hollow polymer fiber reinforced composite materials based on phase change materials according to claim 1, characterized in that, The phase change material used to prepare the inner mold includes one or more combinations of paraffin wax, fatty acids, inorganic hydrated salts, and organic sugar alcohols; the solid-liquid phase change material contains thermally conductive fillers.

3. The molding method for heterogeneous hollow polymer fiber reinforced composite materials based on phase change materials according to claim 2, characterized in that, The fatty acid is selected from any one or more combinations of acetic acid, decanoic acid, lauric acid, pentadecanoic acid, myristic acid, and palmitic acid; the inorganic hydrated salt is selected from any one or more combinations of CaCl2·6H2O, Na2SO4·10H2O, Na2HPO4·12H2O, CH3COONa·3H2O, Na2HPO4·12H2O, CH3COONa·3H2O, Ba(OH)2·8H2O, and MgCl2·6H2O; the organic sugar alcohol is selected from any one or more combinations of xylitol, erythritol, and D-mannitol.

4. The molding method for heterogeneous hollow polymer fiber reinforced composite materials based on phase change materials according to claim 2, characterized in that, The thermally conductive filler is selected from one or more of graphite, graphene, metal powder, and carbon nanotubes.

5. The molding method for heterogeneous hollow polymer fiber reinforced composite materials based on phase change materials according to claim 1, characterized in that, The barrier layer is formed by coating and drying an aqueous composition of a film-forming substance and a plasticizer; the film-forming substance is polyvinyl alcohol and the plasticizer is glycerin.

6. The molding method for heterogeneous hollow polymer fiber reinforced composite materials based on phase change materials according to claim 1, characterized in that, In the aqueous composition, the mass ratio of polyvinyl alcohol, glycerin and water is (1-10):(0.5-5):100, and the thickness of the barrier layer formed is 0.01-2 mm.

7. The molding method for heterogeneous hollow polymer fiber reinforced composite materials based on phase change materials according to claim 1, characterized in that, The prepreg material mentioned in step (4) includes reinforcing fibers and matrix resin, wherein the reinforcing fibers are one of carbon fiber, glass fiber, and aramid fiber; and the matrix resin is epoxy resin.

8. The molding method for heterogeneous hollow polymer fiber reinforced composite materials based on phase change materials according to claim 1, characterized in that, In step (5), the first temperature is lower than the phase transition temperature of the solid-liquid phase change material.

9. The molding method for heterogeneous hollow polymer fiber reinforced composite materials based on phase change materials according to claim 1, characterized in that, In step (6), the second temperature is higher than the phase transition temperature of the solid-liquid phase change material.

10. The molding method for heterogeneous hollow polymer fiber reinforced composite materials based on phase change materials according to claim 1, characterized in that, In step (7), the irregular cavity has at least one opening; the size of the opening is not limited, and it is a molding method for an irregular cavity polymer fiber reinforced composite material with a very small opening or an approximately closed structure.

Images