A special mold for the preparation of a thermoplastic resin-based composite laminate structure

Abstract

The present application proposes a special mold for thermoplastic resin-based composite laminated structure preparation, which is composed of a male mold, a guide column, a female mold and a backing plate. The relationship among them is that the backing plate and the female mold are combined in a clearance fit manner, and under the condition of compression, the backing plate can ensure that the prepreg does not flow out from the edge of the female mold groove when it flows at high temperature; the male mold and the female mold are clearance fit, the convex head of the male mold is pressed into the groove of the female mold, which ensures that the prepreg in the female mold groove is pressed; there are four guide columns in total, which are in the guide holes of the female mold and the male mold when the mold is matched, and play a guiding role. The mold groove backing plate can ensure convenient demolding after preparation without affecting the molding; the reserved gap after the male mold and the female mold are matched provides space for the prepreg lamination, and the gap between the female mold and the male mold can be flexibly adjusted by using a certain thickness of gasket on both sides of the upper surface of the female mold groove; after the preparation of the laminated structure is completed and the backing plate is disassembled, the mold opening groove facilitates the opening of the female and male molds.

Description

Technical Field

[0001] This invention provides a special mold for preparing thermoplastic resin-based composite material laminated structures. It is suitable for the preparation of thermoplastic resin-based composite materials and adopts a design combining a bottom pad and a concave mold to facilitate smooth demolding after the thermoplastic resin-based composite material laminated structure is prepared, thereby meeting the application requirements for the preparation of thermoplastic resin-based composite material laminated structures. It belongs to the field of aerospace science and technology. Background Technology

[0002] Thermoplastic resin-based composites (such as carbon fiber reinforced polyetheretherketone and glass fiber reinforced polyamide) are increasingly widely used in aerospace, rail transportation, and high-end medical devices due to their excellent impact resistance, recyclability, and rapid prototyping capabilities. A typical manufacturing process is hot pressing: prepregs are layered and placed in a mold, heated to above the resin's melting point under pressure to fully melt and impregnate it, and then cooled and solidified under a given pressure to obtain the laminated structure. In this process, the mold tooling not only provides the molding space but is also a key determinant of product quality, dimensional accuracy, and production efficiency. The molding process of thermoplastic resin-based composites poses significant challenges to mold design, with the most prominent common problems being difficulty in demolding and product damage. On the one hand, thermoplastic resins have low viscosity and good fluidity in their high-temperature molten state, allowing them to fully adhere to the mold cavity surface and form a tight physical contact. Simultaneously, the polar functional groups in the resin may undergo chemical adsorption or weak bonding with the surface of the metal mold (usually mold steel or aluminum alloy), leading to a significant "mold sticking" phenomenon after cooling. On the other hand, the molding temperature of thermoplastic resin-based composites is typically above 300℃ (taking polyetheretherketone as an example), while the coefficient of thermal expansion of the mold material differs from that of the composite material layers. During cooling and shrinkage, the shrinkage rate of the composite material is often greater than that of the metal mold, further increasing the clamping force between the product and the mold. Traditional fixed molds lack an active demolding mechanism in their design, often relying on ejector pins or plates for forced ejection. Forced ejection can lead to stress concentration at the interfaces within the laminated structure, causing irreversible damage such as delamination, warping, or fiber buckling. This is especially problematic for thinner or more complexly layered components, resulting in a high scrap rate. Therefore, how to design a mold tooling that can both ensure molding accuracy and achieve non-destructive and convenient demolding has become a technical problem that urgently needs to be solved in the field of thermoplastic resin-based composite material preparation.

[0003] Based on the characteristics of thermoplastic resin-based composite molding, a specialized mold needs to be designed that facilitates demolding without affecting the precision and quality of the molded structure. This invention employs a combination design of a male and female die with a detachable bottom platen, transforming the traditional "forced ejection" demolding method into an "active release" strategy. After thermoforming, demolding is achieved without damage by removing the bottom platen of the die. This invention provides a specialized mold for the fabrication of thermoplastic resin-based composite laminate structures, addressing existing problems. Summary of the Invention

[0004] To ensure smooth demolding during the preparation process and to obtain a thermoplastic resin-based composite laminated structure with molding quality meeting usage requirements, while also guaranteeing the precision of the structural components during demolding, this invention provides a dedicated mold for preparing thermoplastic resin-based composite laminated structures. The technical solution is as follows: Figure 1 This is a schematic diagram of a special mold used for preparing laminated structures of thermoplastic resin-based composite materials. It consists of a punch 1, guide pillars 2, a die 3, and a backing plate 4. All components are made of 310S stainless steel. The relationship between them is as follows: the backing plate 4 and the die 3 are combined in a clearance fit. Under compression conditions, the backing plate 4 can ensure that the prepreg does not flow out from the edge of the groove in the die 3 when it flows at high temperature. The punch and die are in a clearance fit, and the punch head is pressed into the groove of the die to ensure that pressure is applied to the prepreg in the groove of the die. There are four guide pillars in total. When the mold is engaged, the guide pillars are in the guide holes of the die and the punch, which play a guiding role.

[0005] The specific structural form of the punch 1 is shown in [reference needed]. Figure 2 The total thickness of the punch is 3.7 mm, and the thickness of the punch head 1a is 1.7 mm. It is used to press against the groove of the die. The guide hole 1b is a through hole with a diameter of 6 mm. It is used to guide the guide post 2 during the mating process of the die and the punch. The guide post 2, with a diameter of 6 mm, is used to guide the engagement process of the die and the punch.

[0006] The specific structural form of the cavity mold 3 is shown in [reference needed]. Figure 3 The cavity groove 3a has a depth of 2 mm and is used to place the thermoplastic resin-based composite prepreg. A cavity pad groove 3b is designed at the bottom of the cavity for the pad to support the material in the bottom groove. This groove has a depth of 2 mm. The cavity guide hole 3c is a stepped hole used for positioning in the guiding direction of the guide post. The large hole has a diameter of 6 mm and the small hole has a diameter of 3 mm. The cavity release groove 3d has a length of 4 mm, a width of 2 mm, and a depth of 1.5 mm.

[0007] The specific structural form of the pad 4 is shown in [reference]. Figure 4 It is used to fit the groove of the die backing plate and support the thermoplastic resin-based composite prepreg in the bottom die groove. The thickness of the backing plate is 2 mm.

[0008] In the preparation of thermoplastic resin-based composite laminated structures, a backing plate is placed in a groove to support the bottom. Prepreg strips cut into 14mm wide rectangular strips are then placed into the cavity groove according to process requirements. The punch is pressed into the cavity, and four guide pillars are placed into the guide holes after the cavity and punch are fitted together. Depending on the thickness of the molded structure, shims of appropriate thickness are placed on both sides of the upper surface of the cavity to adjust the molding thickness. The mold containing the prepreg is placed in a molding press and molded under given pressure and temperature. After the laminated structure is formed, the mold, guide pillars, and backing plate are removed. The cavity and punch are opened through the mold release groove to easily remove the completed laminated structure.

[0009] The advantages and beneficial effects of this invention are as follows: 1. The mold groove pad ensures easy demolding after preparation without affecting the molding process; 2. The clearance reserved after the punch and die are fitted together provides space for the prepreg to be stacked. The clearance between the die and the punch can be flexibly adjusted by using shims of a certain thickness on both sides of the upper surface of the die groove. 3. After the stacked structure is completed and the pad is removed, the mold release groove facilitates the opening of the concave and convex molds. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the mold of the present invention.

[0011] Figure 2 This is a schematic diagram of punch 1.

[0012] Figure 3 This is a schematic diagram of die 3.

[0013] Figure 4 This is a schematic diagram of pad 4.

[0014] Figure 5 is a schematic diagram of the layup method used in the preparation process of this invention.

[0015] Figure 1 The serial numbers and symbols in the text are explained as follows: 1a. Protruding head; 1b. Guide hole; 3a. Die groove; 3b. Die backing groove; 3c. Die guide hole; 3d. Die release groove; Detailed Implementation

[0016] Please see Figures 1-5As shown, this invention discloses a mold for preparing thermoplastic resin-based composite laminated structures, mainly composed of a punch 1, guide pillars 2, a die 3, and a backing plate 4; all components are made of 310S stainless steel; their relationship is as follows: the backing plate 4 and the die 3's die backing plate groove cooperate to provide support for the thermoplastic resin-based composite prepreg in the die groove; the punch 1's protrusion is pressed into the die groove for cooperation; and the guide pillar is guided through the guide holes of the punch and die. During operation, shims can be added to both sides of the die to adjust the relative height of the punch and die, thereby adjusting the spatial height within the groove and achieving thickness adjustment for the laminated structure preparation.

[0017] Example 1: Fabrication of a sensing-functional polyetheretherketone / carbon fiber (PEEK / CF) reinforced composite-GH4169 metal plate laminate structure Step 1: Preparation of raw materials for the laminated structure Prepare the following raw materials for the fabrication of the sensing functional polyetheretherketone / carbon fiber (PEEK / CF) reinforced composite-GH4169 metal plate laminate structure (hereinafter referred to as "laminated structure"): 0° and 90° PEEK / CF prepregs, PEEK resin film, sensing functional precursor, and metal sheet. A schematic diagram of the laminate is attached. Figure 5 As shown.

[0018] Step 2: Mold closing First, place the pad 4 into the groove 3b of the die pad, and then place the raw materials required for the preparation of the laminated structure, such as 0° and 90° PEEK / CF prepreg, PEEK resin film, sensing functional precursor, and metal sheet, according to the attached... Figure 5 The stacked layers are placed into the cavity groove 3a of the die. Then, with the punch head 1a engaging with the cavity groove 3a, the punch 1 and the die 3 are brought together. At the same time, four guide pins 2 are placed into the guide holes 1b of the punch 1. The guide pins 2 engage with the guide holes 1b of the punch 1 and the guide holes 3c of the die 3 to achieve a guiding function. The space between the punch head 1a and the cavity groove 3a can be adjusted by placing a shim of appropriate thickness between the punch 1 and the die 3 according to the amount of material being prepared.

[0019] Step 3: Compression molding Place the mold containing the layered raw materials into the molding machine, and mold it under the conditions of 1-2 MPa and 360-380℃ as displayed on the machine, with a holding time of 5-20 minutes; after the holding time is over, turn off the machine and cool it to room temperature under the holding pressure.

[0020] Step 4: Demolding After the molding press cools to room temperature, the pressure is released, and the mold is removed and opened. Under the appropriate conditions, with the punch 1 at the bottom and the die 3 and backing plate 4 at the top, the four guide pillars 2 will detach on their own under gravity. Use a screwdriver to pry open the die release groove 3d, and the die 3 and punch 1 will separate. The backing plate 4 can detach from the die 3 under gravity. After the backing plate 4 and die 3 separate, only the resulting laminated structure remains in the die groove 3a of the die 3. At this point, the resulting sensor-functional PEEK / CF reinforced composite-GH4169 metal plate laminated structure can be easily removed. The design of the backing plate 4 facilitates the smooth demolding of the laminated structure.

Claims

1. A special mold for preparing thermoplastic resin-based composite laminated structures, characterized in that: It consists of a punch, guide pillars, a die, and a backing plate. The relationship between them is as follows: the backing plate and the die are combined with a clearance fit. Under compression conditions, the backing plate ensures that the prepreg does not flow out from the edge of the groove in the die when it is flowing at high temperature. The punch and the die are in a clearance fit, and the punch head is pressed into the groove in the die to ensure that pressure is applied to the prepreg in the groove of the die. There are four guide pillars in total. When the mold is engaged, the guide pillars are in the guide holes of the die and the punch, which play a guiding role.

2. The special mold for preparing thermoplastic resin-based composite laminated structures according to claim 1, characterized in that: The punch has a total thickness of 3.7 mm and a protrusion thickness of 1.7 mm, and is used to press against the groove of the die. The guide hole is a through hole with a diameter of 6 mm, and is used to guide the guide post during the mating process of the die and the punch.

3. The special mold for preparing thermoplastic resin-based composite laminated structures according to claim 1, characterized in that: The guide post has a diameter of 6 mm and is used to guide the die and punch during their mating process.

4. A special mold for preparing thermoplastic resin-based composite laminated structures according to claim 1, characterized in that: The cavity groove is 2 mm deep and is used to place the thermoplastic resin-based composite prepreg. A cavity pad groove is designed at the bottom of the cavity for the pad to support the material in the bottom groove. This groove is 2 mm deep. The cavity guide hole is a stepped hole for positioning in the guiding direction of the guide post. The large hole diameter is 6 mm and the small hole diameter is 3 mm. The cavity release groove is 4 mm long, 2 mm wide and 1.5 mm deep.

5. A special mold for preparing thermoplastic resin-based composite laminated structures according to claim 1, characterized in that: The pad is used to fit the groove of the die pad and support the thermoplastic resin-based composite prepreg in the die groove. The thickness of the pad is 2 mm.

6. A method for preparing a laminated structure of thermoplastic resin-based composite materials, characterized in that: Specifically, it involves the fabrication of a sensor-functional polyetheretherketone / carbon fiber PEEK / CF reinforced composite-GH4169 metal plate laminate structure. The steps include the following: Step 1: Preparation of raw materials for the laminated structure Prepare the 0° and 90° PEEK / CF prepregs, PEEK resin film, sensing precursor, and metal sheet material stack required for the fabrication of the sensing functional polyether ether ketone / carbon fiber PEEK / CF reinforced composite-GH4169 metal plate laminate structure. Step 2: Mold closing First, place the backing plate into the groove of the die backing plate. Then, sequentially place the 0° and 90° PEEK / CF prepregs, PEEK resin film, sensing precursor, and metal sheet material required for the laminated structure into the groove of the die. Next, with the punch head engaged with the die groove, fit the punch and die together. Simultaneously, place four guide pillars into the guide holes of the punch. The guide pillars will engage with the guide holes of the punch and the die groove to achieve a guiding function. Adjust the spatial distance between the punch head and the die groove by placing shims of appropriate thickness according to the amount of material to be prepared. Step 3: Compression molding Place the mold containing the layered structural material into the molding machine, and mold it under the conditions of 1-2 MPa pressure and 360-380℃ as displayed on the machine, with a holding time of 5-20 min; after the holding time is over, turn off the machine and cool it to room temperature under the holding pressure. Step 4: Demolding After the molding press cools to room temperature, release the pressure and remove the mold to open it. Under the matching conditions, place the punch of the mold at the bottom and the die and backing plate at the top. The four guide pillars will fall off by gravity. Use a screwdriver to pry open the die release groove of the die, and the die and punch will separate. The backing plate will separate from the die under gravity. After the backing plate and the die are separated, only the resulting laminated structure remains in the die groove of the die. At this time, take out the resulting sensor-functional PEEK / CF reinforced composite-GH4169 metal plate laminated structure.

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