A combined core mold and a manufacturing method thereof

Abstract

The application provides a combined core mold and a manufacturing method thereof, comprising an inner core and a skin, the skin covering the surface of the inner core, and the two being integrally formed. The integrally formed combined core mold can ensure that the skin and the inner core closely follow each other, so that the size of the combined core mold meets the requirements, and since it is integrally formed, it is not necessary to assemble and disassemble, thereby avoiding the problem that the gap becomes larger due to multiple assembly and disassembly, which affects the quality of the target workpiece. According to the glass transition temperature of the target workpiece to be formed, the inner core of the combined core mold is made of two types of materials, if the inner core is made of water-soluble materials, it can be prepared by itself, which has the advantages of low cost and batch manufacturing; if the inner core is made of low-melting-point alloy materials, rapid melting pouring and rapid melting demolding can be realized, and the combined core mold made of alloy cools down faster, the overall preparation efficiency of the inner core mold will be greatly improved, and the low-melting-point alloy can be repeatedly used through melting-cooling.

Description

Technical Field

[0001] This invention belongs to the field of advanced composite material part molding technology, specifically relating to a combined mandrel and its manufacturing method, particularly to a combined mandrel and its manufacturing method for molding composite material parts with complex variable cross-section hollow structure and smooth inner wall. Background Technology

[0002] In the aerospace field, advanced composite materials specifically refer to materials made by using continuous long fibers (carbon fiber, boron fiber, aramid fiber, etc.) as reinforcements, high-performance polymer resins as matrix, and a certain composite process. Due to their lightweight, high strength, and corrosion resistance, they are widely used in the aerospace, rail transit, energy, and automotive fields for the manufacture of primary load-bearing, secondary load-bearing, and functional structural components. The proportion of advanced composite materials used in structures has even become a direct indicator of their advanced nature.

[0003] Simple structural components such as plates, shells, and beams can be formed using conventionally designed metal molds. However, for complex hollow structural components with variable cross-sections, such as bends and air intakes, it is necessary to design a special mandrel that matches the shape of its internal cavity. To achieve a high-quality, smooth, and defect-free inner wall, the mandrel should have a rigid surface and meet the requirement of not undergoing significant deformation under the high temperature and high pressure (130℃, 0.4-0.6 MPa) conditions of conventional autoclave processes.

[0004] Based on the above requirements, the core molds currently used in the industry for molding complex variable cross-section hollow structural parts are usually steel composite core molds, which are composed of different blocks connected to form the core mold as a whole. This type of core mold has problems such as high design and processing difficulty, high assembly precision requirements, and increased assembly gaps after multiple disassemblies and reassemblies. These problems affect the quality of the parts and lead to high manufacturing costs for such parts, becoming an important factor restricting the further increase in the proportion of advanced composite materials used. Summary of the Invention

[0005] The purpose of this invention is to provide a combined core mold and its manufacturing method to overcome the above-mentioned technical defects.

[0006] To solve the above-mentioned technical problems, the present invention provides a combined core mold, including an inner core and a skin, wherein the skin covers the surface of the inner core and the two are integrally formed.

[0007] The skin is made of a single layer of woven prepreg.

[0008] The inner core is made of a water-soluble material that is dried and cured.

[0009] The inner core is made of a soluble low-melting-point alloy material that has been cooled and solidified. The low melting point refers to the alloy's melting point being lower than the glass transition temperature (Tg) of the target part.

[0010] The present invention also provides a method for manufacturing a combined core mold, comprising the following steps:

[0011] Step 100: Prepare the skin;

[0012] Step 200: Apply lubricating oil to the inner wall of the cavity of the mating female mold, put the skin into the mating female mold, ensure that the skin is tightly attached without slippage, and then close the mold to align the female mold.

[0013] Step 300: Inject the raw material for preparing the inner core into the mating mold, ensuring that the cavity of the mating mold is filled, and then move the mating mold into the oven for curing.

[0014] Step 400: Remove the mating female mold from the oven and demold to obtain a combined core mold with the inner core surface covered by a skin.

[0015] Step 100 involves preparing the skin, specifically including:

[0016] Clean the cavity surface of the mating female mold and apply mold release agent;

[0017] A single layer of woven prepreg is laid in the upper and lower mold cavities of the mating female mold, and then sealed and cured.

[0018] Remove the encapsulation material and take the skin out of the mating female mold.

[0019] The raw material for preparing the inner core is a soluble, water-soluble material. Step 300 of the preparation process specifically includes:

[0020] The water-soluble polymer solution and high-purity quartz sand are mixed at a mass ratio of 0.12. The mixed sand is then injected into the cavity of the mating female mold using a core shooter to ensure it is completely filled. The mating female mold is then moved into an oven for curing.

[0021] When used to mold target parts with a glass transition temperature Tg ≥ 150℃, the raw material for preparing the inner core is a soluble low-melting-point alloy material. Step 300 of the preparation process specifically includes:

[0022] The low-melting-point alloy block is rapidly heated and melted using an electromagnetic high-frequency heating machine. The molten alloy is poured into the cavity of the mating female mold, ensuring that the alloy fills the cavity. Then, the mating female mold is moved into an oven, kept warm to remove air bubbles, and the oven is closed to allow it to cool naturally.

[0023] The temperature of the oven is higher than the melting point of the low-melting-point alloy.

[0024] After obtaining the combined core mold, the joint between the two skin pieces on its surface is sealed with pressure-sensitive adhesive tape.

[0025] The beneficial effects of this invention are as follows:

[0026] (1) The inner core serves to support the skin. The inner core and the skin are integrally molded to ensure that they fit together tightly and that the external dimensions of the combined core mold meet the requirements. In addition, the skin is made of a single layer of prepreg, which is easy to tear and the product is easy to pull out from the inner cavity after molding.

[0027] (2) The skin of the combined core mold is formed in the steel mating female mold cavity, so that the skin has the same high quality hard smooth surface as the mating female mold cavity, ensuring the surface quality of the inner cavity of the molded part manufactured using the combined core mold.

[0028] (3) Based on the glass transition temperature of the target part to be molded, the inner core of the combined core mold is made of two types of materials: water-soluble materials or low-melting-point alloy materials. If the inner core is made of water-soluble materials, it can be prepared by itself, which has the advantages of low cost and mass production. If the inner core is made of low-melting-point alloy materials, it can achieve rapid melting and casting and rapid melting and demolding. In addition, the combined core mold made of alloy cools down faster, which greatly improves the overall preparation efficiency of the inner core mold. Furthermore, the low-melting-point alloy can be repeatedly used through melting and cooling.

[0029] To make the above description of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the upper mold and upper skin of the mating female mold.

[0031] Figure 2 This is a structural diagram of the lower mold and lower skin of the mating female mold.

[0032] Figure 3 This is a schematic diagram of the structure of the mating female mold after the mold is closed.

[0033] Figure 4 This is a schematic diagram of the skin structure.

[0034] Figure 5 This is a schematic diagram of the combined core mold.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Upper skin; 2. Upper mold of mating female mold; 3. Lower skin; 4. Lower mold of mating female mold; 5. Female mold of mating; 6. Skin; 7. Combined core mold. Detailed Implementation

[0037] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0038] It should be noted that, in this invention, the upper, lower, left, and right in the figure are regarded as the upper, lower, left, and right of the combined core mold described in this specification.

[0039] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0040] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0041] This invention provides a combined core mold; please refer to [link / reference]. Figure 4 and Figure 5 It includes an inner core and a skin 6. The skin 6 covers the surface of the inner core, and the two are integrally formed. It should be noted that the shapes of the skin 6, the inner core, and the combined core mold 7 are all the same as the shape of the target part.

[0042] Compared to the traditional method of assembling and combining parts to form a core mold, the one-piece molded core mold can ensure that the skin 6 and the inner core fit together tightly, thus ensuring that the external dimensions of the core mold 7 meet the requirements. Moreover, since it is one-piece molded, there is no need for assembly or disassembly, avoiding the problem of increased gaps caused by repeated assembly and disassembly, which affects the quality of the target part.

[0043] Skin 6 is made of a single layer of woven prepreg, specifically, a single layer of glass fiber woven prepreg. The prepreg fibers are mainly glass fiber and carbon fiber, the prepreg resin Tg≥150℃, and the thickness of skin 6 is 0.2-0.3mm.

[0044] The reason why the skin 6 is made of a single layer of prepreg is because it is easy to tear and the product can be easily pulled out of the inner cavity after molding. That is, when making the target part later, the skin 6 can be torn directly and the product can be pulled out.

[0045] The inner core can be made by drying and curing a soluble water-soluble material, or by cooling and curing a soluble low-melting-point alloy material. To be precise, when making all target parts, the inner core of the composite core mold 7 can be made by using a soluble water-soluble material.

[0046] However, for target parts with a glass transition temperature Tg ≥ 150℃, in order to shorten the manufacturing time, a soluble low-melting-point alloy material can be used to manufacture the inner core of the combined core mold 7. Here, low melting point means that the melting point of the alloy is lower than the glass transition temperature Tg of the target part. Specifically, the alloy grade with a melting point about 30℃ lower than the Tg of the part is selected, which results in higher manufacturing efficiency.

[0047] Regardless of the material chosen for the core, it must be soluble to allow for repeated recycling. Specifically, after a certain part (such as an air intake) is made, the core can be melted and used as the core material for another part (such as a bent pipe). In other words, there is no need to design the combined core mold 7 in a complex way according to the shape of the product, and it can be shaped arbitrarily, thus shortening the core mold making process.

[0048] The present invention also provides a method for manufacturing a combined core mold, comprising the following steps:

[0049] Step 100, prepare skin 6;

[0050] Step 200: Apply lubricant to the inner wall of the cavity of the mating female mold 5, place the skin 6 into the mating female mold 5, ensuring the skin 6 is tightly fitted without slippage, and close the mold to assemble the mating female mold 5. (See [link to relevant documentation]). Figure 3 The final skin is 6 as shown. Figure 4 As shown;

[0051] Step 300: Inject the raw material for preparing the inner core into the mating mold 5, ensuring that the cavity of the mating mold 5 is filled (in fact, the inner cavity of the skin 6 is filled), and then move the mating mold 5 into the oven for curing.

[0052] Step 400: Remove the mating female mold 5 from the oven and demold to obtain the combined core mold 7 with the inner core surface covered by the skin 6. Please refer to [link / reference]. Figure 5 .

[0053] The mating female mold 5 is made of steel, and the skin 6 is formed on the cavity surface of the steel mating female mold 5, so that the skin 6 has the same high-quality hard and smooth surface as the mating female mold cavity, ensuring the surface quality of the inner cavity of the molded part manufactured using the combined core mold.

[0054] The combined core mold 7 is a shell-core structure, with the outer shell being a skin 6 made of a single layer of composite material and the inner core being a water-soluble or hot-melt body.

[0055] It should be noted that the traditional combination core mold refers to assembling the segmented inner cores into a whole, which only has the inner core. In other words, when making the target part, the part material is in direct contact with the inner core. However, the combination core mold of this embodiment refers to combining the inner core and the skin. The material of the target part is in direct contact with the skin 6 and will not contact the inner core. The skin 6 has a high-quality, hard, and smooth surface, which can ensure that the inner wall of the target part is smooth.

[0056] Step 100 involves preparing the skin 6, specifically including:

[0057] Clean the cavity surface of the mating mold 5, including Figure 1 The mating upper mold 2 shown, and Figure 2 The lower mold of the mating female mold 4 shown is coated with a release agent evenly on the inner surface of the cavity of the upper mold of the mating female mold 2 and the lower mold of the mating female mold 4.

[0058] A single layer of woven prepreg is laid in the upper and lower mold cavities of the mating female mold 5, and then sealed and cured.

[0059] Remove the encapsulation material and take the skin 6 out of the mating mold 5. At this point, the upper skin 1 and lower skin 3 are complete. (Refer to...) Figure 1 and Figure 2 .

[0060] For any target part, the inner core of the composite core mold 7 can be made using a soluble water-soluble material. However, the curing time of soluble water-soluble materials is relatively long, which affects production efficiency. In order to solve this problem, this embodiment classifies the target parts, as shown below:

[0061] (i) When used to mold target parts with a glass transition temperature Tg ≤ 130℃, the raw material for preparing the inner core is a soluble water-soluble material. The preparation process in step 300 specifically includes:

[0062] The water-soluble polymer solution and high-purity quartz sand are mixed at a mass ratio of 0.12. The mixed sand is then injected into the cavity of the mating female mold 5 using a core shooter to ensure it is filled completely. The mating female mold 5 is then transferred to an oven for curing at 130°C. The curing time depends on the size of the core mold and is usually 4-12 hours.

[0063] (i) When used to mold target parts with a glass transition temperature Tg ≥ 150℃, the raw material for preparing the inner core is a soluble low-melting-point alloy material. Step 300 specifically includes the following preparation process:

[0064] The low-melting-point alloy block is rapidly heated and melted using an electromagnetic high-frequency heating machine. The molten alloy is poured into the cavity of the mating female mold 5, ensuring that the alloy fills the cavity. Then, the mating female mold 5 is moved into an oven, kept warm to remove air bubbles, and the oven is closed to allow it to cool naturally.

[0065] Among them, the alloy is selected with a melting point about 30°C lower than the target part's Tg, and the oven temperature is higher than the melting point of the low-melting-point alloy, such as moving the mold into an oven with a temperature about 10°C higher than its melting point.

[0066] (i) When used to form a target part with a glass transition temperature of 130℃≤Tg≤150℃, a water-soluble material that can be dissolved is selected to prepare the inner core.

[0067] The water-soluble polymer solution mentioned above can be polyvinyl alcohol, polyvinylpyrrolidone, or other water-soluble polymer solutions.

[0068] When the combined core mold 7 is used to mold a target part with a glass transition temperature Tg ≤ 130℃, the inner core is made by drying and curing a soluble water-soluble material, resulting in low manufacturing cost. When the combined core mold 7 is used to mold a target part with a glass transition temperature Tg ≥ 150℃, the inner core is made by cooling and curing a fusible low-melting-point alloy material. The alloy is selected with a melting point about 30℃ lower than the glass transition temperature Tg of the part, resulting in higher manufacturing efficiency.

[0069] After obtaining the combined core mold 7, the joint between the two skin pieces on its surface is sealed with pressure-sensitive adhesive tape. Specifically, the joint between the two skin pieces is sealed with pressure-sensitive adhesive tape with a width of 5mm and a thickness of 0.04mm. A release agent is applied to the skin surface to facilitate demolding after the target part is manufactured.

[0070] The shapes of the skin, inner core, and combined core mold all depend on the shape of the target part to be manufactured. Figures 1-5 The examples shown are for illustrative purposes only. In other words, the shapes of the skin, inner core, and combined core mold are not fixed, but vary according to the shape of the target part.

[0071] Following the above-described method for fabricating the composite mandrel, this embodiment fabricates a complex variable cross-section intake component made of composite materials. Because this intake component is located near the hot end of the engine, it is fabricated using carbon fiber prepreg with a glass transition temperature (Tg) of 150°C, based on heat resistance requirements. The inner core is made of a low-melting-point alloy material with a melting point of 120°C. The specific fabrication steps are as follows:

[0072] Step 1: Clean the surface of the female mold cavity and apply release agent;

[0073] Step 2: Lay a single layer of glass fiber woven prepreg with a glass transition temperature of Tg=150℃ on each half of the mating female mold as a skin shell (or use the same brand of prepreg as the part), and then seal and cure.

[0074] Step 3: As Figure 1 , Figure 2 As shown, remove the encapsulation material and take the fiberglass skin off the mold;

[0075] Step 4: Apply a layer of lubricating oil to the inner wall of the mold cavity, then place the skin back into the mold, ensuring the skin adheres tightly without slippage. Figure 3 As shown, the female mold is closed;

[0076] Step 5: Use an electromagnetic high-frequency heating machine to quickly heat and melt the low-melting-point alloy block, and pour the molten alloy into the mold cavity, ensuring that the alloy is basically filled;

[0077] Step 6: Place the mold in an oven at 130℃ and keep it warm for 1 hour to help remove internal air bubbles. Then turn off the oven and let it cool naturally.

[0078] Step 7: As Figure 5 As shown, the mold is removed from the oven and demolded to obtain the combined core mold;

[0079] Step 8: Seal the seam between the two halves of the skin with a 5mm wide and 0.04mm thick pressure-sensitive adhesive tape; apply release agent to the skin surface to complete the treatment.

[0080] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail may be made without departing from the spirit and scope of the present invention.

Claims

1. A method for manufacturing a combined core mold, characterized in that, The combined core mold includes an inner core and a skin, the skin covering the surface of the inner core, and the two are integrally formed; The skin is made of a single layer of woven prepreg; The inner core is made of a water-soluble material that is dried and cured. Alternatively, the inner core may be made of a soluble low-melting-point alloy material that has been cooled and solidified, wherein the low melting point refers to the alloy melting point being lower than the glass transition temperature Tg of the target part. The manufacturing method of the combined core mold includes the following steps: Step 100: Prepare the skin; Step 200: Apply lubricating oil to the inner wall of the cavity of the mating female mold, place the skin into the mating female mold, ensure that the skin is tightly attached without slippage, and close the mating female mold; Step 300: Inject the raw material for preparing the inner core into the mating female mold, ensuring that the cavity of the mating female mold is filled, and then move the mating female mold into an oven for curing; Step 400: Remove the mating female mold from the oven and demold to obtain a combined core mold with the inner core surface covered by a skin.

2. The method for manufacturing the combined core mold as described in claim 1, characterized in that, Step 100, the preparation of the skin, specifically includes: Clean the cavity surface of the mating female mold and apply a release agent; A single layer of woven prepreg is laid in the upper and lower mold cavities of the mating female mold, and then sealed and cured. Remove the encapsulation material and take the skin out of the mating mold.

3. The method for manufacturing the combined core mold as described in claim 1 or 2, characterized in that, The raw material for preparing the inner core is a soluble, water-soluble material. The preparation process in step 300 specifically includes: A water-soluble polymer solution and high-purity quartz sand are mixed at a mass ratio of 0.

12. The mixed sand is then injected into the cavity of the mating female mold using a core shooter to ensure it is completely filled. The mating female mold is then transferred into an oven for curing.

4. The method for manufacturing the combined core mold as described in claim 1 or 2, characterized in that, When used to mold target parts with a glass transition temperature Tg ≥ 150℃, the raw material for preparing the inner core is a soluble low-melting-point alloy material. The preparation process in step 300 specifically includes: The low-melting-point alloy block is rapidly heated and melted using an electromagnetic high-frequency heating machine. The molten alloy is poured into the cavity of the mating female mold, ensuring that the alloy fills the cavity. Then, the mating female mold is moved into an oven, kept warm to remove air bubbles, and the oven is closed to allow it to cool naturally. The temperature of the oven is higher than the melting point of the low-melting-point alloy.

5. The method for manufacturing the combined core mold as described in claim 1, characterized in that, After obtaining the combined core mold, the joint between the two skin pieces on its surface is sealed with pressure-sensitive adhesive tape.

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