Forming method for preventing R-angle prepreg from being stacked

Abstract

The invention belongs to the field of aerospace, and relates to a forming method for preventing R-angle prepreg stacking. The method comprises the steps that after prepreg at the R corner is laid, a laying layer at the R corner needs to be checked, and it is guaranteed that the laying layer in the R corner area is not bridged; measuring the size of an inner R angle according to a part mathematical model, calculating to obtain the filling amount of a triangular area, and manufacturing a special silk twisting strip by using a silk twisting machine; filling the triangular area with a thread twisting strip, checking the filling area, and observing the filling amount; all laying material pieces of the part are completed, and a piece of demolding cloth matched with an R angle is cut according to the size of the R angle in the part; paving a layer of demolding cloth at the corresponding position of the inner R angle; and 6, a layer of Airpad black silica gel strip is laid in the remaining area of the H-shaped or T-shaped composite material structural part, and meanwhile, the Airpad black silica gel strip is fixed to the tool molded surface through an adhesive tape.

Description

Technical Field

[0001] The invention belongs to the field of aerospace and relates to a molding method for preventing R-corner prepreg stacking. Background Art

[0002] Composite materials have many advantages such as high specific strength, high specific modulus, corrosion resistance, and strong designability. In recent years, they have been widely used in high-tech industries such as aviation and aerospace. Their usage accounts for a growing proportion of the total weight of aircraft structures. All-composite aircraft are gradually emerging, and the application of composite materials in helicopters has developed to the main load-bearing structural parts. H-type, C-type, and T-type parts are relatively difficult to form. The R angle of the parts has a small curvature or is close to a 90° right angle. After the parts are formed, prepreg is prone to accumulation at the R angle, forming R angle wrinkles.

[0003] After this type of parts are laid and bagged, they are sent to the autoclave for curing. During the temperature rise stage of curing, the resin in the prepreg will soften. Under the action of gravity, the resin will flow downward. After reaching the pressurized temperature, the pressure is maintained for a period of time, which will cause the prepreg on the edge to stack up at the R corner, causing R corner wrinkles and glue accumulation problems, thus affecting the part's appearance quality and assembly accuracy. Summary of the invention

[0004] Purpose of the invention: The present invention solves the problems of wrinkles and glue accumulation at the inner R corners of H-shaped, C-shaped and T-shaped parts, and provides a molding process method for structural parts to prevent R corner prepreg stacking. When the parts are laid, a black silicone strip is used at the edge of the part margin area and a release cloth is added to the inner R corner for fixing. During the curing process, the pulling force between the prepreg and the Airpad black silicone strip is increased.

[0005] Technical solution:

[0006] Provided is a molding method for preventing R-corner prepreg stacking, comprising:

[0007] Step 1: After laying the prepreg at the R corner, check the ply at the R corner to ensure that there is no bridging in the ply at the R corner area;

[0008] Step 2: According to the part digital model, measure the size of the inner R angle, calculate the size of the filling amount of the triangular area, and use a twisting machine to make a special twisted wire strip;

[0009] Step 3: Use twisted wire strips to fill the triangular area, check the filled area, and observe the filling amount;

[0010] Step 4: After all the ply sheets of the part are completed, cut a stripping cloth that matches the R angle according to the size of the R angle inside the part;

[0011] Step 5: Lay a layer of release cloth at the corresponding position of the inner R angle;

[0012] Step 6: Lay a layer of Airpad black silicone strip on the remaining area of ​​the H-shaped and T-shaped composite structural parts, and fix it to the tooling surface with tape.

[0013] Furthermore, the calculation formula of the twisted wire width H is:

[0014] H=(2R 2 -0.5πR 2 )*1.1;

[0015] R is the radius of the inner corner.

[0016] Furthermore, a layer of Airpad black silicone strip is laid in the residual area of ​​the H-shaped and T-shaped composite structural parts, including:

[0017] Cut out a 40mm wide Airpad black silicone strip and place it outward between the part line and the allowance line.

[0018] Furthermore, after the twisted wire strips are filled, the method further comprises:

[0019] Use the method of pre-drawing once to check whether the filling of the twisted wire strips is too little or too much.

[0020] Furthermore, the width of the stripping cloth is 10-15 mm.

[0021] Furthermore, the method further comprises:

[0022] During the laying process, it is necessary to check the laying condition of each layer of prepreg in the R corner area of ​​the part.

[0023] Furthermore, the release sheet is not allowed to bridge with the original laminate.

[0024] Beneficial effects: For H-type and T-type composite structural parts, due to the particularity of their structure, during the laying, bag making and curing process, in the molten state, excessive resin is very easy to stack at the R corner of the H-type and T-type composite structural parts under the action of gravity. At the same time, the filling area of ​​the twisted wire strip is overfilled, which easily leads to the stacking of the prepreg at the R corner of the part, causing wrinkles, glue accumulation and excessive thickness at the R corner. After adopting this method, first, the pulling force between the prepreg of the part itself and the Airpad black silicone strip is increased; second, by controlling the filling amount of the twisted wire strip in the triangular area, the prepreg of the H and T-type composite structural parts is prevented from stacking at the R corner, causing the thickness of the part to exceed the tolerance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the twisted wire filling area.

[0026] Figure 2 This is a diagram for placing black silicone. DETAILED DESCRIPTION

[0027] The present invention provides a molding method for preventing the accumulation of R-corner prepreg of a composite material structural part, and the steps are as follows:

[0028] Step 1: After laying the prepreg at the R corner, check the ply at the R corner to ensure that there is no bridging in the ply at the R corner area;

[0029] Step 2: According to the part digital model, measure the size of the inner R angle, calculate the size of the filling amount of the triangular area, and use a twisting machine to make a special twisted wire strip;

[0030] Step 3: Use twisted wire strips to fill the triangle area. Figure 1 As shown, check the filling area and observe the filling amount;

[0031] Step 4: After all the ply sheets of the part are completed, cut a stripping cloth that matches the R angle according to the size of the R angle inside the part;

[0032] Step 5: Lay a layer of release cloth at the corresponding position of the inner R angle. Figure 2 As shown, the release sheet is not allowed to bridge with the original ply;

[0033] Step 6: Lay a layer of Airpad black silicone strip on the remaining area of ​​the H-shaped and T-shaped composite structural parts, and fix it to the tooling surface with tape.

[0034] During the laying process, it is necessary to check the laying condition of each layer of prepreg in the R corner area of ​​the part.

[0035] Furthermore, after the upper mold "C" structure is laid, the size of the inner R angle is measured according to the part digital model, and the calculation formula (2R 2 -0.5πR 2 )*1.1 to get the width of the twisted wire strip;

[0036] Further, the obtained prepreg of twisted wire strip width is placed in a twisting machine to produce twisted wire strip width, the quality of the twisted wire strip is checked, and the twisted wire strips of the required specifications of the twisted wire strips with poor quality are removed;

[0037] Further, after the lower mold "C" shape and the upper mold "C" shape are laid, the twisted wire strips are filled into the triangular area at the corresponding position ( Figure 1 ), and check the filling of the twisted wire strips;

[0038] Furthermore, after the twisted wire strips are filled, a pre-drawing method is used to check whether the twisted wire strips are filled too little or too much;

[0039] Further, continue to complete the part laying and check the laying quality of the R corner area;

[0040] Furthermore, after the part is laid up, a strip of demoulding cloth with a width of 10-15 mm is manually cut and placed in the R corner area inside the part;

[0041] Further, cut out a 40mm wide Airpad black silicone strip ( Figure 2 ), place the black silicone strip outward along the part line and the allowance line, and use tape to fix it on the non-part surface of the tooling.

[0042] Furthermore, a vacuum bag is made and the parts are sent into an autoclave for curing and forming.

[0043] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that the technical solutions of the invention can be modified or replaced by equivalents without departing from the scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A molding method for preventing R-corner prepreg stacking, characterized in that: include: Step 1: After laying the prepreg at the R corner, check the ply at the R corner to ensure that there is no bridging in the ply at the R corner area; Step 2: According to the part digital model, measure the size of the inner R angle, calculate the size of the filling amount of the triangular area, and use a twisting machine to make a special twisted wire strip; Step 3: Use twisted wire strips to fill the triangular area, check the filled area, and observe the filling amount; Step 4: After all the ply sheets of the part are completed, cut a stripping cloth that matches the R angle according to the size of the R angle inside the part; Step 5: Lay a layer of release cloth at the corresponding position of the inner R angle; Step 6: Lay a layer of Airpad black silicone strip on the remaining area of ​​the H-shaped and T-shaped composite structural parts, and fix it to the tooling surface with tape.

2. The method according to claim 1, characterized in that The calculation formula of twisted wire width H is: H=(2R 2 -0.5πR 2 )*1.1; R is the radius of the inner corner.

3. The method according to claim 2, characterized in that Lay a layer of Airpad black silicone strip in the remaining area of ​​H-shaped and T-shaped composite structural parts, including: Cut out a 40mm wide Airpad black silicone strip and place it outward between the part line and the allowance line.

4. The method according to claim 3, characterized in that After the twisted wire strips are filled, the method further comprises: Use the method of pre-drawing once to check whether the filling of the twisted wire strips is too little or too much.

5. The method according to claim 4, characterized in that The width of the stripping cloth is 10-15mm.

6. The method according to claim 1, characterized in that The method further comprises: During the laying process, it is necessary to check the laying condition of each layer of prepreg in the R corner area of ​​the part.

7. The method according to claim 1, characterized in that The release sheet is not allowed to bridge with the original laminate.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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