An integrated composite material engine hood and its preparation process

Abstract

An integrated composite engine hood and a preparation process thereof belong to the technical field of automobile engine hoods. The integrated composite engine hood includes a load-bearing structure formed by hot-pressing and compounding a surface layer and a continuous glass fiber composite sheet with glass fibers arranged in a cross-weaving direction. A reinforcing rib layer is formed by hot-pressing and injection molding a side of the load-bearing structure away from the surface layer. The beneficial effect of the present invention is that the present invention realizes the structural integration of the engine hood, reduces the manufacturing process, reduces the manufacturing cost, ensures that the product has high dimensional stability while meeting the requirements of pedestrian protection, and improves the coating performance and environmental protection level.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile engine hoods, and in particular to an integrated composite material engine hood and a preparation process thereof. Background Art

[0002] At present, new energy vehicles widely use composite materials in the exterior covering parts of the whole vehicle. Among them, the engine hoods of passenger cars are mostly made of polypropylene (PP) as the base material. The large linear expansion coefficient of PP material causes the geometric dimensional accuracy of the product to be unstable. Moreover, with the change of ambient temperature, the clearance and surface difference between the exterior covering parts of the whole vehicle fluctuate greatly, which seriously affects the perceived quality of customers. The current engine hood products are composed of two parts, the inner panel and the outer panel. The inner and outer panels are connected by gluing. Since the inner and outer panels are usually made of different materials, their linear expansion coefficients are different. Under the service conditions of alternating hot and cold, it is easy to cause problems such as poor quality of Class A curved surface. In addition, the existing product structure and manufacturing process have the characteristics of multi-piece and multi-process, which increases the manufacturing cost and prolongs the manufacturing cycle. In addition, the gluing process has a large environmental risk. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides an integrated composite material engine hood and a preparation process thereof, which realizes structural integration, reduces manufacturing processes, reduces manufacturing costs, ensures that the product has high dimensional stability while meeting pedestrian protection requirements, and improves coating performance, meeting Class A curved surface requirements.

[0004] To achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve its technical problem is: the integrated composite material engine hood includes a load-bearing structure formed by hot-pressing a surface layer and a continuous glass fiber composite sheet with glass fibers arranged in a cross-directional direction, and the load-bearing structure is hot-pressed and injection-molded on a side away from the surface layer to form a reinforcing rib layer.

[0005] The continuous glass fiber composite sheet comprises a unidirectional continuous glass fiber composite layer I, a unidirectional continuous glass fiber composite layer II and a bidirectional continuous glass fiber composite layer which are sequentially stacked along the surface of the surface layer, and the glass fibers in the unidirectional continuous glass fiber composite layer I and the unidirectional continuous glass fiber composite layer II are cross-arranged in weaving direction.

[0006] The unidirectional continuous glass fiber composite layer I includes a unidirectional glass fiber woven sheet layer I and a PP material layer I formed by chemical grafting modification and impregnation and coating on its surface. The thickness of the unidirectional continuous glass fiber composite layer I is set to 0.25-1 mm, and the mass fraction of glass fiber in the unidirectional continuous glass fiber composite layer I is 10%-30%.

[0007] The unidirectional continuous glass fiber composite layer II includes a unidirectional glass fiber woven sheet layer I and a PP material layer II impregnated and coated on its surface. The thickness of the unidirectional continuous glass fiber composite layer II is set to 0.25-1 mm, and the mass fraction of glass fiber in the unidirectional continuous glass fiber composite layer II is 10%-30%.

[0008] The bidirectional continuous glass fiber composite layer includes a bidirectional glass fiber woven sheet layer and a PP material layer III impregnated and coated on its surface. The glass fibers in the bidirectional glass fiber woven sheet layer are cross-arranged in the weaving direction. The thickness of the bidirectional continuous glass fiber composite layer is set to 0.25-1 mm, and the mass fraction of the glass fibers in the bidirectional continuous glass fiber composite layer is 20%-60%.

[0009] The surface layer includes a PC sheet and a paint film layer sprayed thereon, wherein the PC sheet is a PC sheet without glass fiber added or a PC sheet with 5% to 10% by mass of glass fiber added.

[0010] The reinforcing rib layer is formed by hot-pressing injection molding of long glass fiber reinforced PP material, the reinforcing rib layer is configured as mesh reinforcing ribs, the height of the reinforcing rib layer is configured as 10 to 60 mm, and the thickness of each strip rib in the reinforcing rib layer is configured as 1 to 4 mm.

[0011] The linear expansion coefficient of the engine hood is 7.63×10 -6 ~14.2×10 -6 m / (m·k), torsional stiffness is 50~110N·mm / deg, lateral stiffness is 0~1mm, and angular stiffness is 50~110N / mm.

[0012] A preparation process of an integrated composite material engine hood comprises the following steps:

[0013] Step 1: Lay the surface layer and the continuous glass fiber composite sheet in layers and cut them into a preset shape;

[0014] Step 2: Position the cut and formed laminated sheets and bake them to soften them;

[0015] Step 3: Place the softened laminated sheet in a hot pressing mold and position it for pre-pressing;

[0016] Step 4: Using a compression molding machine to form a reinforcing rib layer on the side of the laminated sheet away from the surface layer, and obtaining a semi-finished engine hood after pressure maintenance;

[0017] Step 5: Spraying on the surface of the surface layer of the semi-finished engine hood to form a paint film.

[0018] The baking and softening temperature in step 2 is set to 200-300° C., and the softening time is 20-40 seconds; the mold clamping pressure of the mold clamping pre-pressing in step 3 is 700-800 tons; the holding pressure in step 4 is 50-75 MPa, and the holding time is 6-15 seconds.

[0019] The beneficial effects of the present invention are:

[0020] 1. The present invention forms an integrated structure by stacking and laying a surface layer and a continuous glass fiber composite sheet with cross-weaving of glass fibers, hot pressing and compounding them, and then reinforcing ribs by hot pressing and injection molding. This achieves structural integration and reduces the linear expansion coefficient of the entire engine hood. The entire preparation process does not require gluing, which not only meets the mechanical properties of the front hood of a passenger car, but also improves the coating performance and dimensional stability of the parts. It also reduces the preparation process, improves the preparation efficiency, reduces the manufacturing cost, and the prepared product is more environmentally friendly.

[0021] 2. The continuous glass fiber composite sheet involved in the present invention comprises a unidirectional continuous glass fiber composite layer I, a unidirectional continuous glass fiber composite layer II and a bidirectional continuous glass fiber composite layer. The glass fibers of the unidirectional continuous glass fiber composite layer I and the unidirectional continuous glass fiber composite layer II are arranged in a cross-weaving direction, and the glass fibers in the bidirectional continuous glass fiber composite layer are arranged in a cross-weaving direction. By adding a certain mass fraction of continuous glass fibers to each continuous glass fiber composite layer, the thermal expansion coefficient of the entire engine hood can be controlled within 7.63×10 -6 ~14.2×10 -6 m / (m·k), which is much smaller than the expansion coefficient of existing products, improves the thermal stability of product size, and further reduces the clearance and surface difference fluctuations between the outer covering parts of the whole vehicle.

[0022] 3. Each continuous glass fiber composite layer involved in the present invention is a PP material layer impregnated and coated on the surface of the glass fiber woven sheet layer, and the PP base material in the unidirectional continuous glass fiber composite layer I connected to the surface layer is modified by chemical grafting, so that the surface layer and the continuous glass fiber composite sheet do not need to be bonded together by gluing, but are softened by heating and molded. At high temperature, due to the fluidity of PP in each continuous glass fiber composite layer and the good interface compatibility between the chemically grafted PP and PC, the surface layer and the continuous glass fiber composite sheet can be firmly bonded, which not only meets the mechanical properties of the passenger car engine hood and improves the environmental protection level of the finished product, but also simplifies the preparation process and improves the overall structural strength and stability.

[0023] 4. The present invention forms a reinforcing rib layer on the side of the continuous glass fiber composite sheet away from the surface layer by compression molding during the hot pressing process of each continuous glass fiber composite layer, thereby improving the structural strength and rigidity of the engine hood, further improving the mechanical properties of the product and extending its service life.

[0024] In summary, the present invention realizes the structural integration of the engine hood, reduces the manufacturing process, reduces the manufacturing cost, ensures that the product has high dimensional stability while meeting the requirements of pedestrian protection, and improves the coating performance and environmental protection level. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The following is a brief description of the contents expressed in the drawings of the present invention and the symbols in the drawings:

[0026] Figure 1 It is a structural schematic diagram of the present invention;

[0027] Figure 2 for Figure 1 AA section view;

[0028] Figure 3 for Figure 2 The structural diagram of the middle enlarged part B;

[0029] The marks in the above figures are: 1. surface layer, 11. PC sheet, 12. paint film layer, 2. continuous glass fiber composite sheet, 21. unidirectional continuous glass fiber composite layer I, 22. unidirectional continuous glass fiber composite layer II, 23. bidirectional continuous glass fiber composite layer, 3. reinforcement rib layer, 4. groove, 5. nut tube insert, 6. latch structure. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0031] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The specific implementation scheme of the present invention is: Figure 1 to Figure 3 As shown, an integrated composite material engine hood includes a load-bearing structure formed by hot-pressing a surface layer and a continuous glass fiber composite sheet with glass fibers arranged in a cross-weaving direction. A reinforcing rib layer is formed by hot-pressing injection molding on a side of the load-bearing structure away from the surface layer, thereby realizing the integration of the engine hood structure. In addition, the continuous glass fiber composite sheet with glass fibers arranged in a cross-weaving direction reduces the linear expansion coefficient of the entire engine hood. In addition, the entire preparation process does not require gluing, and the prepared product is more environmentally friendly, reduces the preparation steps, improves the preparation efficiency, and reduces the manufacturing cost. It not only meets the mechanical properties of the front hood of a passenger car, but also improves the coating performance and dimensional stability of the parts.

[0034] Specifically, the surface layer includes a PC (polycarbonate) sheet and a paint film layer sprayed thereon. The PC sheet can be set to a PC sheet without adding glass fiber, or can be set to a PC sheet with 5% to 10% by mass of glass fiber added. After adding glass fiber to the PC sheet, during the hot pressing process of the PC sheet and the continuous glass fiber composite sheet, after the PC and the base material in the continuous glass fiber composite sheet are fused, the internal glass fibers are cross-connected, which can further increase the structural strength and stability after hot pressing fusion.

[0035] Specifically, the continuous glass fiber composite sheet includes a unidirectional continuous glass fiber composite layer I, a unidirectional continuous glass fiber composite layer II and a bidirectional continuous glass fiber composite layer which are stacked in sequence along the surface of the surface layer. The glass fibers in the unidirectional continuous glass fiber composite layer I and the unidirectional continuous glass fiber composite layer II are cross-stacked in weave direction, and the glass fibers in the bidirectional continuous glass fiber composite layer are also cross-arranged in weave direction, which can improve the compressive strength and stiffness of the entire continuous glass fiber composite sheet.

[0036] The unidirectional continuous glass fiber composite layer I comprises a unidirectional glass fiber woven sheet layer I and a PP material layer I formed by chemical grafting modification and impregnation and coating on its surface, wherein the unidirectional glass fiber woven sheet layer I comprises unidirectionally arranged untwisted glass fiber yarns, and the preparation method of the unidirectional continuous glass fiber composite layer I is that the unidirectionally arranged untwisted glass fiber yarns and polypropylene fibers are alternately and closely arranged, and the polypropylene fibers are melted and impregnated with glass fibers under high temperature rolling to form. The raw material of the polypropylene fiber is polypropylene formed by chemical grafting modification, that is, by adding grafting monomer maleic anhydride to PP resin, heating and melting and mixing under the action of initiator isopropylbenzene peroxide to carry out grafting reaction, and the initiator is heated to 190-230°C, decomposes to generate active free radicals, and when the active free radicals contact with the grafting monomer maleic anhydride, the unstable bonds are opened, and the free radicals are melted with polypropylene free radicals to form PP grafting free radicals, and then chain transfer reaction is carried out to terminate. The chemically grafted modified polypropylene can improve its bonding strength with polycarbonate (PC) at high temperature, and can improve the melting stability between the unidirectional continuous glass fiber composite layer I and the surface layer. The thickness of the unidirectional continuous glass fiber composite layer I is set to 0.25-1 mm.

[0037] The unidirectional continuous glass fiber composite layer II includes a unidirectional glass fiber woven sheet layer I and a PP material layer II impregnated and coated on its surface. The preparation method of the unidirectional continuous glass fiber composite layer II is the same as that of the unidirectional continuous glass fiber composite layer I. Both are formed by unidirectionally arranged untwisted glass fiber yarns and polypropylene fibers alternately and closely arranged, and the polypropylene fibers are melted and impregnated with glass fibers under high temperature rolling. The thickness of the unidirectional continuous glass fiber composite layer II is set to 0.25-1 mm.

[0038] The bidirectional continuous glass fiber composite layer includes a bidirectional glass fiber woven sheet layer and a PP material layer III impregnated and coated on its surface. The glass fibers in the bidirectional glass fiber woven sheet layer are cross-arranged in the weaving direction. The preparation method of the bidirectional continuous glass fiber composite layer is that the untwisted glass fiber yarns are alternately and closely arranged and then stacked and alternately arranged with polypropylene fibers. Under high-temperature rolling, the polypropylene fibers are melted and impregnated with the crossed glass fibers to form a bidirectional continuous glass fiber composite layer. The thickness of the bidirectional continuous glass fiber composite layer is set to 0.25-1 mm.

[0039] The mass fraction of glass fiber in the unidirectional continuous glass fiber composite layer I is 10% to 30%, the mass fraction of glass fiber in the unidirectional continuous glass fiber composite layer II is 10% to 30%, and the mass fraction of glass fiber in the bidirectional continuous glass fiber composite layer is 20% to 60%, so that the thermal expansion coefficient of the entire engine hood is controlled within 7.63×10 -6 ~14.2×10 -6 m / (m·k), which is much smaller than the expansion coefficient of existing products, improves the thermal stability of product size, and further reduces the clearance and surface difference fluctuations between the outer covering parts of the whole vehicle.

[0040] Specifically, the reinforcement layer is formed by hot-pressing injection molding of long glass fiber reinforced PP material, and the reinforcement layer is arranged as a mesh reinforcement. The density of the mesh reinforcement can be increased at the position with greater load on the load-bearing structure according to the actual service conditions of the engine hood, and vice versa. The height of the reinforcement layer is set to 10-60 mm, and the thickness of each strip rib in the reinforcement layer is set to 1-4 mm.

[0041] In addition, the reinforcement layer also integrates the structural design for the installation of automobile parts or the realization of functions. For example, in the process of one-piece molding of the reinforcement layer, grooves for installing sealing strips, nut tube inserts for installing engine hood locks, and pin structures for fixing the engine hood to the body are also integrally injection-molded according to installation requirements, thereby improving the stability and structural strength of the installation structure.

[0042] The preparation process of the above-mentioned integrated composite material engine hood comprises the following steps:

[0043] Step 1: Lay the surface layer and the continuous glass fiber composite sheet in layers and cut them into a preset shape.

[0044] The surface layer, the unidirectional continuous glass fiber composite layer I, the unidirectional continuous glass fiber composite layer II and the bidirectional continuous glass fiber composite layer are stacked and laid, and cut into a suitable shape by heat treatment equipment.

[0045] Step 2: Position the cut laminated sheets and bake them to soften them.

[0046] After the cut and formed laminated sheets are positioned by a positioning fixture, they are grabbed by a robot and taken to an infrared oven for baking and softening. The baking and softening temperature is 200 to 300° C. and the softening time is 20 to 40 seconds.

[0047] Step 3: Place the softened laminated sheet in the hot pressing mold and position it for pre-pressing. The clamping pressure is 700-800t. During the high-temperature hot pressing process of the four-layer sheet, the PP resin between the unidirectional continuous glass fiber composite layer I, the unidirectional continuous glass fiber composite layer II and the bidirectional continuous glass fiber composite layer melts and flows at high temperature. At the same time, the chemically grafted PP base material in the unidirectional continuous glass fiber composite layer I melts and flows with the polycarbonate (PC), so that the layers of the sheet are melted and bonded, and the glass fibers between the layers of the sheet are in contact, realizing the hot pressing fusion into an integrated structure. The setting of two layers of cross-arranged glass fibers and one layer of bidirectional glass fibers improves the overall structural strength, rigidity and stability.

[0048] Step 4: A reinforcing rib layer is formed by injection molding on the side of the laminated sheet away from the surface layer through a compression molding machine, and a semi-finished engine hood is obtained after pressure maintenance.

[0049] The laminated sheet material hot-melt pressed into one in step 3 is placed into the mold of a compression molding machine, and hot-melt long glass fiber reinforced PP material is injected into the side of the laminated sheet away from the surface layer to form a reinforcing rib layer, a groove for installing a sealing strip, a nut tube insert for installing a hood lock buckle, and a pin structure for fixing the hood to the body after pressing. The pressing pressure is 700-800t, and the pressure is maintained for 6-15s at a pressure of 50-75MPa. After the pressure is maintained, the semi-finished product is taken out.

[0050] Step 5: Spray polyurethane on the surface of the surface layer of the semi-finished engine hood to form a paint film.

[0051] The thermal expansion coefficient of the engine cover obtained by the above preparation process is 7.63×10 -6 ~14.2×10 -6 m / (m·k), torsional stiffness is 50~110N·mm / deg, lateral stiffness is 0~1mm, and angular stiffness is 50~110N / mm, which meets the mechanical performance requirements of passenger car engine hoods. Moreover, since the surface layer of the engine hood is PC material and the inner layer is PP material, it can save costs compared to using PC material alone, and can improve the coating performance of the engine hood surface compared to using PP material alone, meeting the A-level curved surface requirements.

[0052] Comparative Example 1

[0053] The existing passenger car engine hood includes an inner panel and an outer panel. The inner panel is made of long glass fiber reinforced PP material, and the outer panel is made of talcum powder reinforced EPDM toughened PP material. The inner panel and the outer panel are bonded together by adhesive. After the inner panel and the outer panel are processed and formed separately, the adhesive is applied between the inner panel and the outer panel, and then the inner panel and the outer panel are bonded together by die extrusion. The whole preparation process is complicated, and the linear expansion coefficient of the obtained product is 50×10 -6 ~90×10 -6 m / (m·k), torsional stiffness is 50~110N·mm / deg, lateral stiffness is less than 1mm, angular stiffness is 50~110N / mm, and the non-polarity of the outer panel surface makes the painting performance of the engine hood poor.

[0054] It can be seen from Comparative Example 1 and the embodiments that the linear expansion coefficient of the product obtained by the present invention is much smaller than that of the existing products, which means that the thermal stability of the product obtained by the present invention is better, and the mechanical properties are equivalent to those of the original products, which meets the mechanical properties required by the engine hood of a passenger car. In addition, the entire preparation process of the present invention does not require gluing, and is formed in one piece through hot melt pressing and hot compression injection molding. The prepared product is more environmentally friendly and has a more stable structure, which reduces the preparation process, improves the preparation efficiency, and reduces the manufacturing cost.

[0055] The above description is only used to illustrate some principles of the present invention. This specification is not intended to limit the present invention to the specific structure and application scope shown and described. Therefore, all corresponding modifications and equivalents that may be used belong to the patent scope applied for by the present invention.

Claims

1. An integrated composite engine hood, characterized in that: It comprises a load-bearing structure formed by hot-pressing and compounding a surface layer and a continuous glass fiber composite sheet with glass fibers arranged in a cross-weaving direction, and a reinforcing rib layer is formed by hot-pressing and injection molding a side of the load-bearing structure away from the surface layer; The continuous glass fiber composite sheet comprises a unidirectional continuous glass fiber composite layer I, a unidirectional continuous glass fiber composite layer II and a bidirectional continuous glass fiber composite layer which are sequentially stacked along the surface of the surface layer, and the glass fibers in the unidirectional continuous glass fiber composite layer I and the unidirectional continuous glass fiber composite layer II are cross-arranged in weaving direction; The unidirectional continuous glass fiber composite layer I includes a unidirectional glass fiber woven sheet layer I and a PP material layer I formed by chemical grafting modification and its surface is impregnated and coated; the unidirectional continuous glass fiber composite layer II includes a unidirectional glass fiber woven sheet layer I and a PP material layer II impregnated and coated on its surface; the bidirectional continuous glass fiber composite layer includes a bidirectional glass fiber woven sheet layer and a PP material layer III impregnated and coated on its surface, and the glass fibers in the bidirectional glass fiber woven sheet layer are cross-arranged in the weaving direction.

2. The one-piece composite engine hood according to claim 1, characterized in that: The surface layer includes a PC sheet and a paint film layer sprayed thereon, and the PC sheet is configured as a PC sheet without adding glass fiber or a PC sheet with adding 5% to 10% by mass of glass fiber.

3. The one-piece composite engine hood according to claim 1, characterized in that: The thickness of the unidirectional continuous glass fiber composite layer I is set to 0.25-1 mm, and the mass fraction of glass fiber in the unidirectional continuous glass fiber composite layer I is 10%-30%.

4. The one-piece composite engine hood according to claim 1, characterized in that: The thickness of the unidirectional continuous glass fiber composite layer II is set to 0.25-1 mm, and the mass fraction of glass fiber in the unidirectional continuous glass fiber composite layer II is 10%-30%.

5. The one-piece composite engine hood according to claim 1, characterized in that: The thickness of the bidirectional continuous glass fiber composite layer is set to 0.25-1 mm, and the mass fraction of glass fiber in the bidirectional continuous glass fiber composite layer is 20%-60%.

6. The one-piece composite engine hood according to claim 1, characterized in that: The reinforcing rib layer is formed by hot-pressing injection molding of long glass fiber reinforced PP material, the reinforcing rib layer is configured as a mesh reinforcing rib, the height of the reinforcing rib layer is configured as 10-60 mm, and the thickness of each strip rib in the reinforcing rib layer is configured as 1-4 mm.

7. The one-piece composite engine hood according to claim 1, characterized in that: The linear expansion coefficient of the engine hood is 7.63×10 -6 ~14.2×10 -6 m / (m•k), torsional stiffness is 50~110N·mm / deg, lateral stiffness is 0~1mm, and angular stiffness is 50~110N / mm.

8. A process for preparing the integrated composite engine hood according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: Lay the surface layer and the continuous glass fiber composite sheet in layers and cut them into a preset shape; Step 2: Position the cut and formed laminated sheets and bake them to soften them; Step 3: Place the softened laminated sheet in a hot pressing mold and position it for pre-pressing; Step 4: Using a compression molding machine to form a reinforcing rib layer on the side of the laminated sheet away from the surface layer, and obtaining a semi-finished engine hood after pressure maintenance; Step 5: Spraying on the surface of the surface layer of the semi-finished engine hood to form a paint film.

9. The process for preparing the integrated composite engine hood according to claim 8, characterized in that: The baking and softening temperature in step 2 is set to 200-300° C., and the softening time is 20-40 seconds; the clamping pressure of the clamping pre-pressing in step 3 is 700-800 tons; the holding pressure in step 4 is 50-75 MPa, and the holding time is 6-15 seconds.

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