Composite material fragile cover and preparation method thereof

Abstract

The invention discloses a composite material fragile cover and a preparation method thereof.The two end faces of a fragile cover body are provided with a pressing plate and a bottom plate respectively, grooves are formed in the front face and the back face of the fragile cover body, each groove comprises a rectangular cross-shaped groove formed along the circle center and an inclined V-shaped annular groove formed in the annular direction, and the included angle of each inclined V-shaped annular groove is 30-45 degrees; the fragile cover body is made of fiber woven cloth, a sandwich felt and an epoxy resin matrix. Grooves in special shapes are prefabricated in the two faces of the fragile cover. The strength and continuity of the fiber woven fabric are utilized to ensure that the fragile cover is crushed into four uniform and complete blocks after being impacted, and the flange area is complete. The composite material fragile cover only needs one-time curing forming, the forming process is simple, performance is excellent, stability is good, and good application and popularization prospects are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of fragile covers, and in particular relates to a composite material fragile cover and a preparation method thereof. Background Art

[0002] The frangible cover is an important component of the launch tube of an aircraft, and has a direct impact on the reliability and rapid response capability of the launch. When designing the frangible cover, it must meet the requirements of airtightness, electromagnetic shielding performance, and the ability to open quickly and reliably during launch. Due to the excellent mechanical properties, anisotropy, and designability of composite materials, it has become one of the preferred materials for making frangible covers. In recent years, a variety of frangible cover forms have emerged.

[0003] The Chinese invention patent with publication number CN102313491A discloses a method for manufacturing an integral top-breaking composite launch box cover. A fragile cover including a frame and a frame is prepared through three-time curing molding. During launch, the fragile cover breaks as a whole to make way for the passage. The fragile cover needs to be cured three times. The structure includes tic-tac-toe-shaped wooden strips, polyurethane foam, aluminum embedded parts, and glass fiber cloth. The manufacturing process is relatively complicated and the process flow is long.

[0004] The Chinese invention patent with publication number CN110806151A discloses a fragile front cover of an aircraft and a method for preparing the same. The method uses a compression molding injection molding process to manufacture a reinforcement layer, and then uses a foaming process to manufacture a front cover body on the upper end surface of the reinforcement layer, polishes the upper end surface of the front cover body and sprays a heat-resistant coating, and finally manufactures a sealing gasket, wherein the reinforcement layer material is glass fiber cloth. The preparation of the fragile cover requires two molding processes, compression molding injection molding and foaming, respectively, and the molding process is relatively complicated.

[0005] The Chinese invention patent with publication number CN1844840A discloses a fragile composite film cover, which is made of high-strength glass fiber cloth and epoxy resin, with the fiber directions laid at 0° and 90°, cross notches pre-made in the weak area and high-strength wires laid to ensure that the film can crack in four petals at the same time. However, the fragile composite film cover cannot be broken along the circumferential direction, and is only suitable for launch tubes with low alignment requirements, and its scope of application is relatively limited.

[0006] The Chinese invention patent with publication number CN107932817A discloses a top-breaking epoxy plastic fragile cover and its preparation method. The fragile cover is in the shape of a round arch, and the main body is made of epoxy foam plastic. The structure is relatively simple and can be broken at the root. However, the epoxy foam adopts physical foaming, that is, adding inorganic hollow fillers. Since the hollow fillers have a low density, they will float up during the curing process, resulting in uneven density in the direction of gravity, thereby affecting the pressure bearing and crushing performance of the fragile cover, so the control requirements of the process are relatively high.

[0007] In summary, the existing methods for making fragile covers generally have problems such as complex preparation process and strict process control, which leads to high cost of fragile covers. Although some fragile covers have simple structures, they have a narrow scope of application. In addition, domestic research institutions and enterprises have conducted little research on the integrity of fragile covers, and there is still much room for improvement in the integrity of fragile covers. Summary of the invention

[0008] In order to solve the above problems, the present invention aims to provide a composite material fragile cover and a preparation method thereof.

[0009] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: a composite material fragile cover, comprising a fragile cover body, a pressure plate and a bottom plate are respectively arranged on both end surfaces of the fragile cover body, grooves are opened on the front and back surfaces of the fragile cover body, the grooves include a rectangular cross groove opened along the center of the circle and an oblique V-shaped annular groove opened along the annular direction, and the angle of the oblique V-shaped annular groove is 30 to 45 degrees,

[0010] The raw materials of the fragile cover body include fiber woven cloth, sandwich felt and epoxy resin matrix.

[0011] Furthermore, the fragile cover body includes a middle area and an annular area, the middle area includes a rectangular cross groove and four equally divided middle sector areas divided by the rectangular cross groove, the annular area includes an annular flange area, an oblique V-shaped annular groove is opened on the annular surface in the annular flange area, and a plurality of annular circular mounting holes are evenly arranged in the annular flange area.

[0012] Furthermore, the two end surfaces of the fragile cover body are respectively provided with an outer surface annular groove and an inner surface annular groove, and a pressure plate and a bottom plate are respectively installed on the outer surface annular groove and the inner surface annular groove.

[0013] Furthermore, the diameter of the outer surface annular groove is 1 to 3 mm larger than the diameter of the inner surface annular groove, the inner diameter of the pressure plate is consistent with the outer surface annular groove, and the diameter of the bottom plate is the same as the inner surface annular groove.

[0014] Furthermore, the pressing plate and the bottom plate are made of aluminum alloy or low carbon steel.

[0015] A method for preparing a composite material fragile cover comprises the following steps:

[0016] Step 1: Cutting fiber woven fabric and chopped fiber mat;

[0017] Step 2: laying the cut fiber woven fabric and the chopped fiber mat on the mold bottom plate in sequence, and evenly scraping the resin layer by layer to make the resin completely saturate the fiber woven fabric or the chopped fiber mat;

[0018] Step 3: Cover the mold cover, push it into the molding machine, and heat press to cure;

[0019] Step 4: After curing, demould after natural cooling;

[0020] Step 5: Process the shape, circular mounting holes and rectangular cross grooves on a CNC milling machine, and process the oblique V-shaped annular grooves on a CNC lathe.

[0021] Furthermore, the fiber woven fabric in step one is one of glass fiber, carbon fiber, and aramid fiber 0° / 90° woven fabric, which is respectively laid on the inner and outer surfaces of the composite material fragile cover; the chopped fiber felt material is selected from chopped glass fiber felt, carbon fiber felt, and nylon felt.

[0022] Furthermore, the resin in step 2 is one of epoxy resin, unsaturated resin or vinyl resin, preferably epoxy resin.

[0023] Furthermore, in the step three, the molding pressure is 0.2-2 MPa, the curing temperature is room temperature-200° C., and the curing time is 1-24 h, preferably 0.5 MPa and 90° C. for 3 h.

[0024] Compared with the prior art, the present invention has the following advantages: epoxy resin, fiber woven cloth and chopped fiber felt are selected as the raw materials for the fragile cover body, and grooves of special shapes are prefabricated on both sides of the fragile cover. The strength and continuity of the fiber woven cloth are utilized to ensure that the fragile cover is broken into four uniform and complete pieces after being impacted, and the flange area is intact. Different from traditional woven cloth as sandwich material, since the chopped fiber felt is approximately isotropic on the plane, there are no residual burrs after fracture, and the fracture strength is also stable. In addition, the cross-section of the annular groove adopts an oblique V-shape, which can control the flushness of the flange after fracture to within 0.4mm. The composite fragile cover of the present invention only needs one-time curing and molding, and has a simple molding process, superior performance, good stability, and good prospects for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is a side view of a composite material frangible cover of the present invention;

[0027] Figure 2 yes Figure 1 A magnified view of point I;

[0028] Figure 3is a front view of a composite material frangible cover of the present invention;

[0029] In the figure, 1-fragile cover body; 2-pressing plate; 3-bottom plate; 4-circumferential groove on outer surface; 5-circumferential groove on inner surface; 6-fiber woven cloth; 7-rectangular cross groove; 8-oblique V-shaped circumferential groove; 9-circular mounting hole; 10-annular flange area. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but it should not be understood that the scope of the subject matter described in the present invention is limited to the following embodiments. Without departing from the above-mentioned technical ideas of the present invention, various modifications, substitutions and changes made according to the common technical knowledge and customary means in the field are included in the scope of the present invention.

[0031] A composite material fragile cover mainly consists of a fragile cover body 1, a pressing plate 2, and a bottom plate 3. The fragile cover body 1 is composed of a fiber woven fabric 6, a sandwich felt, and an epoxy resin matrix. The pressing plate 2 and the bottom plate 3 are made of aluminum alloy or low carbon steel. The inner diameter of the pressing plate 2 is the same as the annular groove 4 on the outer surface, and the diameter of the bottom plate is the same as the annular groove 5 on the inner surface.

[0032] The fragile cover body 1 is divided into an annular flange area 10, a rectangular cross groove 7, an oblique V-shaped annular groove 8, and an intermediate fan-shaped area 11. The annular flange area 10 is evenly provided with a plurality of annular circular mounting holes 9. The front and back sides of the fragile cover body 1 are provided with rectangular cross grooves 7 and oblique V-shaped annular grooves 8, wherein the oblique V-shaped annular grooves 8 have an angle of 30 to 45 degrees, and the diameter of the outer surface annular groove 4 is larger than that of the inner surface annular groove 51 to 3 mm.

[0033] A method for preparing a composite material fragile cover, the method comprising the following steps:

[0034] Step 1: cutting the fiber woven fabric 6 and the chopped fiber mat;

[0035] Step 2: laying the cut fiber woven fabric 6 and the chopped fiber mat on the mold bottom plate in sequence, and evenly scraping the resin layer by layer to make the resin completely saturate the fiber woven fabric 6 or the chopped fiber mat;

[0036] Step 3: Cover the mold cover, push it into the molding machine, and heat press to cure;

[0037] Step 4: After curing, demould after natural cooling;

[0038] Step 5: Process the shape, holes and cross grooves on a CNC milling machine, and process the oblique V-shaped annular grooves on a CNC lathe.

[0039] The woven fabric in step one is one of glass fiber, carbon fiber, aramid fiber 0° / 90° woven fabric, which is laid on the inner and outer surfaces of the composite material fragile cover respectively; the chopped mat material is selected from chopped glass fiber mat, carbon fiber mat, nylon mat, and is mainly selected according to the strength requirements of the composite material fragile cover. The resin in step two is one of epoxy resin, unsaturated resin or vinyl resin, preferably epoxy resin; the molding pressure in step three is 0.2~2MPa, the curing temperature is room temperature~200℃, and the curing time is 1~24h, preferably 0.5MPa, 90℃ curing for 3h;

[0040] Example: Refer to Figure 1 and Figure 2 The composite material fragile cover provided by the present invention comprises a fragile cover body 1, a pressing plate 2, and a bottom plate 3. The fragile cover body 1 is composed of a fiber woven fabric 6, a sandwich felt, and an epoxy resin matrix. The pressing plate 2 and the bottom plate 3 are made of aluminum alloy or low carbon steel. The inner diameter of the pressing plate 2 is the same as the outer diameter of the annular groove 4 on the outer surface; the inner diameter of the bottom plate 3 is the same as the annular groove 5 on the inner surface.

[0041] Reference Figure 3 The fragile cover body of the present invention is divided into an annular flange area 10, a rectangular cross groove 7, an oblique V-shaped annular groove 8, and an intermediate fan-shaped area 11. The flange area is evenly distributed with a number of annular circular mounting holes 9.

[0042] Specifically, the front and back sides of the fragile cover body 1 of the present invention are provided with a rectangular cross groove 7 and an oblique V-shaped annular groove 8, wherein the oblique V-shaped groove has an angle of 40 degrees, and the diameter of the outer surface annular groove 4 is slightly larger than that of the inner surface annular groove 5 by 2 mm.

[0043] Fragile cover body preparation:

[0044] Step 1: Cut carbon fiber 0 / 90° woven fabric and nylon chopped fiber mat;

[0045] Step 2: Lay one layer of carbon fiber 0 / 90° woven fabric + three layers of chopped fiber mat + one layer of carbon fiber 0 / 90° woven fabric on the mold bottom plate in sequence, and evenly scrape the resin layer by layer to make the resin completely saturate the fiber woven fabric 6 or the chopped fiber mat;

[0046] Step 3: Cover the mold cover plate and push it into the molding machine, with a pressure of 0.5MPa and curing at 90℃ for 3h;

[0047] Step 4: After curing, demould after natural cooling;

[0048] Step 5: Process the shape, holes and cross grooves on a CNC milling machine, and process the oblique V-shaped annular grooves on a CNC lathe.

[0049] The fragile cover prepared according to the above embodiment Figure 3The maximum height of the flange root after fracture is 0.3mm, the fragile cover is evenly divided into petals, and the root is well aligned.

[0050] The above is a detailed introduction to a composite material fragile cover and a preparation method thereof provided by the present invention. This article uses specific examples to illustrate the structure and working principle of the present invention. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A composite material fragile cover, characterized in that: The invention comprises a fragile cover body (1), a pressure plate (2) and a bottom plate (3) are respectively arranged on both end surfaces of the fragile cover body (1), grooves are provided on the front and back surfaces of the fragile cover body (1), the grooves include a rectangular cross groove (7) provided along the center of a circle and an oblique V-shaped annular groove (8) provided along the annular direction, the angle of the oblique V-shaped annular groove (8) is 30 to 45 degrees, The raw materials of the fragile cover body (1) include fiber woven cloth (6), sandwich felt and epoxy resin matrix.

2. The composite material frangible cover according to claim 1, characterized in that: The fragile cover body (1) comprises a middle area and an annular area, the middle area comprising a rectangular cross groove (7) and four equally divided middle sector areas (11) divided by the rectangular cross groove (7), the annular area comprising an annular flange area (10), an oblique V-shaped annular groove (8) provided on the inner annular surface of the annular flange area (10), and a plurality of annular circular mounting holes (9) evenly arranged on the annular flange area (10).

3. The composite material frangible cover according to claim 1, characterized in that: The two end surfaces of the fragile cover body (1) are respectively provided with an outer surface annular groove (4) and an inner surface annular groove (5), and a pressure plate (2) and a bottom plate (3) are respectively installed on the outer surface annular groove (4) and the inner surface annular groove (5).

4. The composite material frangible cover according to claim 3, characterized in that: The diameter of the outer surface annular groove (4) is 1 to 3 mm larger than the diameter of the inner surface annular groove (5), the inner diameter of the pressure plate (2) is consistent with the outer diameter of the outer surface annular groove (4), and the inner diameter of the bottom plate (3) is consistent with the outer diameter of the inner surface annular groove (5).

5. The composite material frangible cover according to claim 3, characterized in that: The pressing plate (2) and the bottom plate (3) are made of aluminum alloy or low carbon steel.

6. A method for preparing a composite material fragile cover according to any one of claims 1 to 5, characterized in that: The following steps are included: Step 1: cutting the fiber woven fabric (6) and the chopped fiber mat; Step 2: laying the cut fiber woven fabric (6) and the chopped fiber mat on the mold bottom plate in sequence, and evenly scraping the resin layer by layer to make the resin completely saturate the fiber woven fabric (6) or the chopped fiber mat; Step 3: Cover the mold cover, push it into the molding machine, and heat press to cure; Step 4: After curing, demould after natural cooling; Step 5: Process the outer shape, the circular mounting hole (9) and the rectangular cross groove (7) on a CNC milling machine, and process the oblique V-shaped annular groove (8) on a CNC lathe.

7. The method for preparing a composite material fragile cover according to claim 6, characterized in that: The fiber woven fabric (6) in step 1 is one of glass fiber, carbon fiber, and aramid fiber 0° / 90° woven fabric, which is laid on the inner and outer surfaces of the composite material fragile cover respectively; the chopped fiber felt material is selected from chopped glass fiber felt, carbon fiber felt, and nylon felt.

8. The method for preparing a composite material fragile cover according to claim 6, characterized in that: The resin in step 2 is one of epoxy resin, unsaturated resin or vinyl resin, preferably epoxy resin.

9. The method for preparing a composite material fragile cover according to claim 6, characterized in that: The molding pressure in step three is 0.2-2 MPa, the curing temperature is room temperature to 200° C., and the curing time is 1-24 h, preferably 0.5 MPa and 90° C. for 3 h.

Images