Composite material skin forming method based on glue blocking measure

Abstract

The invention belongs to the technical field of composite material processing, and provides a composite material skin forming method based on a glue blocking measure, which comprises the following steps: preparing a mold; composite material laying: laying the prepreg on a mold according to a certain laying sequence and angle, and compacting after laying each layer; designing and mounting a glue blocking structure: designing the glue blocking structure according to the shape and the size of the skin and the predicted glue flowing direction, and mounting the glue blocking structure along the edge of the mold or the predicted region where the glue is easy to lose; vacuum bag packaging: covering the surface of the laminated composite material with an isolating membrane and a breathable material, sealing the edge of the vacuum bag with a sealing tape, and connecting a vacuum pipeline; vacuumizing, heating and curing; and demolding and post-processing. The technical problem that resin glue liquid flows during composite material skin forming is solved, the phenomenon of uneven glue liquid loss is reduced, and the composite material skin forming quality and the product percent of pass are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite material forming and processing, and specifically relates to a composite material skin forming method based on glue blocking measures, which is suitable for the manufacture of high-performance composite material skins in the fields of aerospace, automobiles, etc. Background Art

[0002] Composite skins are widely used in aerospace, automotive, and other fields due to their lightweight, high strength, and corrosion resistance. Currently, the main molding methods for composite skins include autoclave molding and vacuum bagging. However, these molding processes often result in uneven resin loss. Excessive loss can lead to localized resin depletion in the skin, compromising its mechanical properties. Insufficient loss can lead to numerous bubbles within the skin, reducing product quality.

[0003] Existing techniques for controlling resin content through the use of adhesive-absorbing materials (such as adhesive-absorbing felt and breathable felt) can lead to complex processes, material waste, and can easily cause problems such as uneven fiber volume fraction and increased porosity. Some adhesive-blocking processes lack strong sealing properties, causing resin to easily overflow from the mold edges. Furthermore, the reliance on high-precision prepregs makes resin flowability difficult to control, leading to dry spots or resin-rich areas, making them incapable of meeting the requirements for high-precision composite skin molding.

[0004] Therefore, there is an urgent need for an effective method to solve the problem of glue flow control during the molding process of composite skins and improve the molding quality of composite skins. Summary of the Invention

[0005] The present invention aims to solve the problem of resin glue flowing during the existing composite skin molding and provides a composite skin molding method based on glue blocking measures. By reasonably setting the glue blocking structure, selecting breathable materials, pressurizing in stages, adjusting the heating rate, optimizing the vacuum pipeline layout and other measures, the flow of resin glue during the composite skin molding process is accurately controlled, the uneven glue loss phenomenon is reduced, and the composite skin molding quality and product qualification rate are improved.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A composite material skin forming method based on glue blocking measures comprises the following steps: Mold preparation: clean, polish and apply release agent to the mold surface; Composite material layup: prepreg is laid on the mold in a certain layup order and angle, and each layer is compacted after laying; Design and installation of glue retaining structure: Design the glue retaining structure according to the shape, size and expected glue flow direction of the skin, and install it along the edge of the mold or in the area where the glue is expected to easily flow; Vacuum bag packaging: After the composite material is laid, the surface is covered with an isolation film and breathable material, the edge of the vacuum bag is sealed with sealing tape, and the vacuum pipeline is connected; Vacuuming and heating curing: Start the vacuum pump to achieve the required vacuum degree in the vacuum bag; according to the predetermined curing process curve, increase the temperature in a gradient and apply pressure in stages; Demolding and post-processing: After cooling, the vacuum pipeline and vacuum bag film are removed, the mold is demoulded and the skin is surface-treated to obtain a composite skin product that meets the design requirements.

[0007] As a further solution of the present invention: the mold preparation is specifically as follows: according to the design requirements of the composite material skin, a molding mold is prepared, and the mold surface is cleaned, polished and coated with a release agent to ensure that the mold surface is smooth to facilitate subsequent demolding operations.

[0008] As a further solution of the present invention: the composite material laying is specifically as follows: according to the design requirements, the composite material prepreg is laid on the mold according to a certain laying order and angle, and during the laying process, it is ensured that the prepreg is closely fitted to the mold surface to avoid wrinkles and bubble defects; each time a layer of prepreg is laid, it is compacted with a pressing roller to expel the air between the layers.

[0009] As a further solution of the present invention: the design of the glue blocking structure is specifically as follows: the glue blocking structure is designed according to the shape, size and expected glue flow direction of the skin; the glue blocking structure includes a glue blocking strip and an auxiliary glue blocking component, and the shape of the glue blocking strip can be customized according to the edge contour of the skin; the auxiliary glue blocking component includes a glue blocking plate and a sealing strip, the glue blocking plate is used to prevent the flow of glue in a larger plane area of ​​the skin, and the sealing strip is used to fill the gap between the glue blocking structure and the mold.

[0010] As a further solution of the present invention: the rubber blocking strip is made of a high-temperature resistant, low-surface-energy material, such as polytetrafluoroethylene or silicone rubber.

[0011] As a further solution of the present invention: the installation of the glue blocking structure is specifically as follows: the glue blocking strip is installed along the edge of the mold or the area where the glue is expected to be easily lost, and the glue blocking strip is fixed to the mold using a high-temperature resistant glue strip; the glue blocking plate is installed so that it fits tightly with the mold surface, and the sealing strip is filled in the contact gap between the glue blocking plate and the mold.

[0012] As a further solution of the present invention: the vacuum bag packaging is specifically: After the layup is completed, the surface of the composite material is covered with a non-porous isolation film, a glass fiber breathable cloth, and sealed with a pressure-sensitive tape; Use 8-10 layers of non-porous isolation film to seal the anti-drop bolts; Then cover the vacuum bag with fiberglass breathable cloth and use sealing tape to seal the edge of the vacuum bag to the mold; Connect the vacuum line to the vacuum bag and connect it to the vacuum pump.

[0013] As a further solution of the present invention: the vacuum bag is made of polyimide material, the vacuum pipeline is a multi-channel vacuum pipeline, and multiple exhaust ports are arranged at the edge and thick area of ​​the part to avoid local gas retention.

[0014] As a further solution of the present invention: the vacuuming and heating curing are specifically as follows: Starting the vacuum pump to evacuate the vacuum bag to a predetermined vacuum level, wherein the predetermined vacuum level is between -0.08 MPa and -0.1 MPa; While evacuating the mold, heat the mold and, according to the predetermined curing process curve, increase the temperature in a gradient and apply pressure in stages to heat the mold and composite material to the curing temperature, so that the resin in the prepreg is fully cured. The pressurization is carried out in stages. When the resin viscosity is the lowest, a low pressure is maintained to allow bubbles to be discharged slowly to prevent the resin from being squeezed out. When the resin is close to gel, full pressure is applied to ensure the density between layers. The low pressure is 0.1 MPa ~ 0.3 MPa and the full pressure is 0.5 MPa ~ 0.7 MPa. The heating rate is slow heating to extend the low viscosity window time of the resin and allow the bubbles to fully migrate to the vacuum pipeline for discharge, wherein the slow heating rate is 1-2°C / min.

[0015] As a further solution of the present invention: the demoulding and post-processing are specifically as follows: After curing is completed, wait for the mold and composite material to cool to room temperature, remove the vacuum pipe and vacuum bag film, and use the demoulding tool to demould the molded composite skin from the mold; The surface of the skin after demoulding is trimmed to obtain a composite material skin product that meets the design requirements.

[0016] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. By setting up a glue-blocking structure, this application can effectively control the flow of resin glue during the molding process of the composite material skin, avoid the problem of excessive or insufficient glue loss, and make the glue evenly distributed inside the skin, thereby improving the density and mechanical properties of the composite material skin, and the product qualification rate can be increased to more than 95%.

[0017] 2. The glue-blocking structure of the present application adopts high-temperature resistant and low-surface-energy materials, which will not react chemically with the composite material, and can stably play the role of glue-blocking during the curing process. At the same time, it is convenient for demoulding operation and does not affect the surface quality of the composite material skin.

[0018] 3. The molding method of the present application is simple to operate. By improving the existing molding process and adding glue blocking measures, there is no need for large-scale modification of the equipment, which reduces production costs and has good economic benefits and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic flow chart of a composite material skin forming method based on glue blocking measures of the present invention; Figure 2 This is a schematic diagram of the structure of the laying of the curing auxiliary material of the present invention; Figure 3 This is a graph showing the relationship between multi-stage pressurization and temperature curves. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be described in more detail below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] In the drawings, the same or similar reference numerals throughout the drawings represent the same or similar elements or elements having the same or similar functions. The described embodiments are only some of the embodiments of the present invention, but not all of the embodiments.

[0022] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0023] The following is combined with Figure 1-3 The embodiments of the present invention are described in detail.

[0024] Example 1 The present invention discloses a composite material skin forming method based on glue blocking measures, which comprises the following steps: (1) Mold preparation: According to the design requirements of the composite skin, prepare the forming mold, clean, polish and apply release agent to the mold surface to ensure that the mold surface is smooth to facilitate subsequent demolding operations.

[0025] (2) Composite material layup: According to the design requirements, the prepreg is laid on the mold in a specific layering order and angle. During the laying process, the prepreg is ensured to fit tightly against the mold surface to avoid defects such as wrinkles and bubbles. After each layer of prepreg is laid, it is compacted with a roller to remove air between the layers.

[0026] (3) Design and installation of rubber retaining structure: (a) Design the adhesive retaining structure based on the skin's shape, size, and expected adhesive flow direction. This retaining structure consists of adhesive strips and auxiliary retaining components. The strips are made of high-temperature-resistant, low-surface-energy materials, such as polytetrafluoroethylene (PTFE) or silicone rubber, and their shape can be customized to the skin's edge contour. The auxiliary retaining components include adhesive plates and sealing strips. The plates are used to prevent adhesive flow in larger flat areas of the skin, while the sealing strips fill the gap between the retaining structure and the mold.

[0027] (b) Install the rubber strip along the edge of the mold or in areas where the adhesive is expected to leak easily. The strip should protrude approximately 2mm from the mold surface. Use high-temperature resistant adhesive tape to secure the strip to the mold, ensuring it is securely installed and not loose. Install the rubber plate so that it fits tightly against the mold surface, and fill the gap between the rubber plate and the mold with sealing tape to ensure a tight seal and prevent the adhesive from leaking out.

[0028] (4) Vacuum bag packaging: After the composite material is laid, it is covered with a non-porous isolation film and breathable material, and sealed with pressure-sensitive tape. 8-10 layers of non-porous isolation film are used to seal the anti-slip bolts. The vacuum bag film is then covered on the glass fiber breathable cloth, and the edges of the vacuum bag film are sealed to the mold with sealing tape to ensure that the vacuum bag is well sealed. The vacuum pipeline is connected to the vacuum bag and connected to the vacuum pump. The breathable material is glass fiber breathable cloth, which is breathable but not glue-permeable, and excludes volatiles and air.

[0029] (5) Vacuuming and curing: Start the vacuum pump and evacuate the vacuum bag to reach a predetermined vacuum level, generally -0.08MPa to -0.1MPa. While evacuating, heat the mold and heat the mold and composite material to the curing temperature according to the predetermined curing process curve. The resin in the prepreg is fully cured. During the curing process, the glue retaining structure can effectively prevent excessive loss of the resin glue and evenly distribute the glue inside the composite material. The vacuum bag is made of polyimide. The vacuum pipeline is a multi-channel vacuum pipeline, and multiple exhaust ports are arranged at the edges and thick areas of the parts to avoid local gas retention.

[0030] The pressurization is performed in stages. When the resin viscosity is at its lowest, maintain a low pressure (e.g., 0.1 MPa to 0.3 MPa) to allow bubbles to slowly escape and prevent resin extrusion. When the resin is close to gelling, apply full pressure (0.5 MPa to 0.7 MPa) to ensure interlayer density.

[0031] The heating rate is slow (1-2°C / min) to extend the low viscosity window time of the resin and allow the bubbles to fully migrate to the vacuum pipeline for discharge.

[0032] (6) Demolding: After curing is complete, the mold and composite material are cooled to room temperature. The vacuum lines and vacuum bagging are removed, and the molded composite skin is carefully removed from the mold using a demoulding tool. The surface of the demoulded skin is then trimmed to obtain a composite skin product that meets the design requirements.

[0033] Example 2 The present invention discloses a composite material skin forming method based on glue blocking measures, which comprises the following steps: Step 1: Mold preparation: Use sandpaper to polish until the color of the mold body appears, use a cleaning agent to remove excess material on the mold surface, wipe the release agent on the mold surface and cure it.

[0034] Step 2: Laying of composite materials: First peel off the release film on the side of the prepreg without direction marking line, lay it to about 20mm outside the anti-slip screw, use scissors to make a hole and insert the screw to fit tightly with the mold, and then peel off the release film on the other side. The joints between prepregs are required to be butt-jointed, with a butt gap of no more than 0.5mm and a butt spacing of no less than 100mm. The butt joints between two adjacent layers of prepreg must be staggered. A hair dryer can be used to heat and drive out bubbles between layers to ensure that the prepreg layers fit together, there is no bridging, and the interlayer compaction has no bridging and a smooth surface. After each layer of prepreg is laid, vacuum compaction is performed at room temperature.

[0035] Step 3: Design and installation of the rubber barrier structure: After the prepreg is laid, place a layer of silicone rubber pad or polytetrafluoroethylene strip around the prepreg as a rubber barrier. The height of the rubber barrier must be higher than the thickness of the prepreg. The rubber barriers need to be trimmed to matching shapes and must be butt-jointed without gaps. They must be fixed with pressure-sensitive tape.

[0036] Step 4: Vacuum bagging: Apply two layers of A4000R non-porous separator film to the prepreg surface, extending at least 5mm beyond the edge of the part. No overlap is allowed. Each layer of A4000R non-porous separator film must be sealed with pressure-sensitive tape to prevent glue overflow during curing. Apply 8-10 layers of A4000R non-porous separator film to each anti-slip bolt and seal the perimeter with pressure-sensitive tape. Apply fiberglass breathable cloth to the separator film surface and finally seal the vacuum bag with vacuum bag film and sealing tape. The two vacuum nozzles should be placed on opposite sides of the facade.

[0037] Step 5: Vacuum curing: After sealing, send it into the autoclave and connect the vacuum system. Check the sealing of the vacuum bag until the vacuum degree meets the requirements. Then arrange the temperature measuring thermocouple, check that there is no excess material, close the tank door, and according to the predetermined curing process curve, increase the temperature according to the gradient and pressurize in stages.

[0038] Step 6: Demolding: Use a spatula to slowly insert the demoulding strip from the margin area between the part and the mold to separate the part from the mold.

[0039] So far, the purpose of the present invention has been achieved.

[0040] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A composite material skin forming method based on glue blocking measures, characterized in that: The following steps are involved: Mold preparation: clean, polish and apply release agent to the mold surface; Composite material layup: prepreg is laid on the mold in a certain layup order and angle, and each layer is compacted after laying; Design and installation of glue retaining structure: Design the glue retaining structure according to the shape, size and expected glue flow direction of the skin, and install it along the edge of the mold or in the area where the glue is expected to easily flow; Vacuum bag packaging: After the composite material is laid, the surface is covered with an isolation film and breathable material, the edge of the vacuum bag is sealed with sealing tape, and the vacuum pipeline is connected; Vacuuming and heating curing: Start the vacuum pump to achieve the required vacuum degree in the vacuum bag; according to the predetermined curing process curve, increase the temperature in a gradient and apply pressure in stages; Demolding and post-processing: After cooling, the vacuum pipeline and vacuum bag film are removed, the mold is demoulded and the skin is surface-treated to obtain a composite skin product that meets the design requirements.

2. A composite material skin forming method based on glue blocking measures according to claim 1, characterized in that: The mold preparation specifically includes: preparing a molding mold according to the design requirements of the composite material skin, cleaning, polishing and applying a release agent to the mold surface to ensure that the mold surface is smooth to facilitate subsequent demoulding operations.

3. The composite material skin forming method based on the glue blocking measure according to claim 1 is characterized in that: The composite material laying process specifically comprises the following steps: laying the composite material prepreg on the mold in a certain laying order and angle according to the design requirements; ensuring that the prepreg is in close contact with the mold surface during the laying process to avoid wrinkles and air bubbles; and compacting each layer of prepreg with a pressing roller to expel air between the layers.

4. The composite material skin forming method based on the glue blocking measure according to claim 1 is characterized in that: The design of the glue blocking structure is specifically as follows: the glue blocking structure is designed according to the shape, size and expected glue flow direction of the skin; the glue blocking structure includes a glue blocking strip and auxiliary glue blocking components, and the shape of the glue blocking strip can be customized according to the edge contour of the skin; the auxiliary glue blocking components include a glue blocking plate and a sealing strip, the glue blocking plate is used to prevent the flow of glue in a larger plane area of ​​the skin, and the sealing strip is used to fill the gap between the glue blocking structure and the mold.

5. A composite material skin forming method based on glue blocking measures according to claim 4, characterized in that: The rubber blocking strip is made of high temperature resistant and low surface energy material, such as polytetrafluoroethylene or silicone rubber.

6. A composite material skin forming method based on glue blocking measures according to claim 4, characterized in that: The installation of the glue blocking structure is specifically as follows: installing the glue blocking strip along the edge of the mold or the area where the glue is expected to be easily lost, and fixing the glue blocking strip on the mold with a high-temperature resistant glue strip; installing the glue blocking plate so that it fits tightly with the mold surface, and filling the contact gap between the glue blocking plate and the mold with a sealing strip.

7. The composite material skin forming method based on the glue blocking measure according to claim 1 is characterized in that: The vacuum bag packaging is specifically: After the layup is completed, the surface of the composite material is covered with a non-porous isolation film, a glass fiber breathable cloth, and sealed with a pressure-sensitive tape; Use 8-10 layers of non-porous isolation film to seal the anti-drop bolts; Then cover the vacuum bag with fiberglass breathable cloth and use sealing tape to seal the edge of the vacuum bag to the mold; Connect the vacuum line to the vacuum bag and connect it to the vacuum pump.

8. A composite material skin forming method based on glue blocking measures according to claim 7, characterized in that: The vacuum bag is made of polyimide material, and the vacuum pipeline is a multi-channel vacuum pipeline. Multiple air extraction ports are arranged at the edge and thick area of ​​the part to avoid local gas retention.

9. The composite material skin forming method based on the glue blocking measure according to claim 1 is characterized in that: The vacuuming and heating curing are specifically as follows: Starting the vacuum pump to evacuate the vacuum bag to a predetermined vacuum level, wherein the predetermined vacuum level is between -0.08 MPa and -0.1 MPa; While evacuating the mold, heat the mold and, according to the predetermined curing process curve, increase the temperature in a gradient and apply pressure in stages to heat the mold and composite material to the curing temperature, so that the resin in the prepreg is fully cured. The pressurization is carried out in stages. When the resin viscosity is the lowest, a low pressure is maintained to allow bubbles to be discharged slowly to prevent the resin from being squeezed out. When the resin is close to gel, full pressure is applied to ensure the density between layers. The low pressure is 0.1 MPa ~ 0.3 MPa and the full pressure is 0.5 MPa ~ 0.7 MPa. The heating rate is slow heating to extend the low viscosity window time of the resin and allow the bubbles to fully migrate to the vacuum pipeline for discharge, wherein the slow heating rate is 1-2°C / min.

10. The composite material skin forming method based on the glue blocking measure according to claim 1, characterized in that: The demoulding and post-processing are specifically as follows: After curing is completed, wait for the mold and composite material to cool to room temperature, remove the vacuum pipe and vacuum bag film, and use the demoulding tool to demould the molded composite skin from the mold; The surface of the skin after demoulding is trimmed to obtain a composite material skin product that meets the design requirements.

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