Preparation method of composite material wallboard type structure co-curing molding soft mold

Abstract

The invention provides a preparation method of a composite material wallboard type structure co-curing forming soft mold. The preparation method comprises the following steps: positioning, mounting, curing and forming a skin process false part on a skin forming mold; laying and curing a rubber soft mold on the skin process false part, wherein the rubber soft mold comprises a first rubber layer and a second rubber layer which are oppositely arranged, and a prepreg layer arranged between the first rubber layer and the second rubber layer; clamping and fixing the skin forming mold, the skin process false part and the rubber soft mold; a machining area is formed on the rubber soft mold in a milling mode, and the size of the machining area is matched with that of the lower flange of the reinforcing rib. According to the method, the size precision of the rubber soft mold and the axial degree of the reinforcing ribs of the composite material stiffened wall plate can be guaranteed, meanwhile, manufacturing of reinforcing rib process fake parts is omitted, the repair work after curing forming of the rubber soft mold is reduced, the machining precision and the production efficiency are improved, and the manufacturing cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of composite material forming, and more specifically, to a preparation method for a co-curing soft mold of a composite material panel structure. Background Art

[0002] Composite materials have a series of advantages such as high specific strength, high specific stiffness, fatigue resistance, good designability, and easy integral forming, and are widely used in the aerospace field. The amount of their use has become an important indicator to measure the advancement of aircraft. The stiffened panel is one of the most commonly used structures of composite materials and is widely used in large-sized wing structures and fuselage structures. The cross-section of the stiffener includes an I-shaped cross-section and an inverted T-shaped cross-section, etc.

[0003] The existing composite material panel structures are generally composed of a composite material skin and a composite material stiffener connected together. Before production, it is necessary to prepare a soft mold to constrain the curing and forming of the composite material stiffener. In the prior art, generally, a process dummy of the stiffener is made in advance, positioned and fixed on the laid rubber soft mold material according to the digital model of the composite material panel, and the soft mold material is cut by an artificial cutting method so that the cut part of the soft mold matches the shape and size of the bottom of the stiffener. Then, the soft mold material and the process dummy of the stiffener are combined and cured. However, during the curing process, the process dummy of the stiffener expands due to heat and easily squeezes the soft mold material, resulting in deformation of the soft mold material at the corresponding position. In addition, due to the poor dimensional accuracy of the artificial cutting of the soft mold material, there is also a certain influence on the axis straightness of the stiffener of the composite material stiffened panel. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] The technical problems to be solved by the present invention are the problems that the existing soft mold material is prone to deformation during the curing process and the existing cutting method affects the axis straightness of the stiffener.

[0006] (2) Technical Solutions

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a preparation method for a co-curing soft mold of a composite material panel structure, including the following steps:

[0009] S1. Position, install and cure a skin process dummy on a skin forming mold;

[0010] S2. Lay and cure a rubber soft mold on the skin process dummy. The rubber soft mold includes a first rubber layer and a second rubber layer arranged oppositely, and a prepreg layer arranged between the first rubber layer and the second rubber layer;

[0011] S3. Clamp and fix the skin forming die, the skin process dummy and the rubber soft mold;

[0012] S4. Milling and cutting a processing area on the rubber soft mold, wherein the size of the processing area matches the size of the lower flange of the stiffener.

[0013] Preferably, the following steps are further included:

[0014] After the milling and cutting is completed, measure the processing area. If the size of the processing area is within the error range, stop the processing. If the size of the processing area is not within the error range, continue the milling and cutting until the size of the processing area meets the error range.

[0015] Preferably, the error range includes: the dimensional error between the processing area and the lower flange of the stiffener is not greater than ±0.25 mm, and the angular error is not greater than ±2°.

[0016] Preferably, both the first rubber layer and the second rubber layer are Airpad rubber, and the prepreg layer is a laminate of 2 - 8 layers of carbon fiber prepreg or a laminate of 2 - 8 layers of glass fiber prepreg.

[0017] Preferably, the skin forming die is provided with a skin process dummy positioning line and laser positioning target holes.

[0018] Preferably, laser positioning targets are installed in the laser positioning target holes, the number M of the laser positioning targets ≥ 4, and the center distance H between adjacent two laser positioning targets ≤ 1 m.

[0019] Preferably, when using a laser tracker to emit positioning laser for positioning, the deviation of each laser positioning target from the positioning laser point is not greater than 0.3 mm.

[0020] Preferably, the size of the processing area is 0.15 mm smaller than the size of the lower flange of the stiffener.

[0021] Preferably, the following steps are further included:

[0022] Manually mill and cut to remove the process allowance so that the size of the processing area is equal to the size of the lower flange of the stiffener.

[0023] Preferably, a CVD composite coating milling cutter with a diameter of 4 mm is used to mill and cut the processing area, the rotational speed of the milling cutter is 12000 rad, the feed rate is 800 mm / min, and the cutting depth is not greater than 0.5 mm.

[0024] (III) Beneficial effects

[0025] The above technical solutions of the present invention have at least the following advantages:

[0026] In the present invention, by first curing and forming a rubber soft mold that matches the surface shape of the skin process dummy, and then milling a processing area that matches the shape and size of the lower flange of the stiffener on the cured rubber soft mold, the preparation of the rubber soft mold is realized, the dimensional accuracy of the rubber soft mold is improved to ensure the axis degree of the stiffener of the co-cured composite stiffened panel, and at the same time, the production of the stiffener process dummy is cancelled, the repair work after the curing and forming of the rubber soft mold is reduced, the processing accuracy and production efficiency are improved, and the preparation cost is reduced. By improving the processing accuracy of the rubber soft mold, the present invention solves the positioning problem of the stiffener combined with the skin during the co-curing process of the composite panel structure, and ensures the axis accuracy of the stiffener bars of the co-cured composite panel. For composite panel structures, especially large-size composite stiffened panel structures, it has certain engineering application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is one of the schematic flowcharts of the preparation method of the co-curing soft mold for the composite panel structure provided by the embodiment of the present invention.

[0029] Figure 2 It is the second schematic flowchart of the preparation method of the co-curing soft mold for the composite panel structure provided by the embodiment of the present invention.

[0030] Figure 3 It is the third schematic flowchart of the preparation method of the co-curing soft mold for the composite panel structure provided by the embodiment of the present invention.

[0031] Figure 4 It is the fourth schematic flowchart of the preparation method of the co-curing soft mold for the composite panel structure provided by the embodiment of the present invention.

[0032] The reference numerals in the drawings are as follows:

[0033] 1, skin forming mold; 2, skin process dummy; 3, rubber soft mold; 4, stiffener; 41, lower flange of stiffener; 31, processing area. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as "connected to" another element, it can be directly connected or indirectly connected to the other element.

[0036] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention, rather than indicating that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention.

[0037] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating relative importance or indicating the number of technical features. In the description of the present invention, the meaning of "a plurality of" is two or more unless otherwise specifically defined. The following describes the specific implementation of the present invention in more detail with reference to specific embodiments:

[0038] As Figures 1 to 4 shown, an embodiment of the present invention provides a method for preparing a co-cured soft mold for a composite material panel structure, including the following steps:

[0039] S1. Position, install and cure a skin process dummy 2 on a skin forming mold 1; specifically, the skin process dummy 2 is consistent with the skin's used material, surface shape, and external dimensions in the digital model of the composite material panel structure;

[0040] S2. Lay and cure a rubber soft mold 3 on the skin process dummy 2. The rubber soft mold includes a first rubber layer and a second rubber layer arranged oppositely, and a prepreg layer disposed between the first rubber layer and the second rubber layer;

[0041] S3. Clamp and fix the skin forming mold 1, the skin process dummy 2, and the rubber soft mold 3;

[0042] S4. Mill and cut a processing area 31 on the rubber soft mold 3. Among them, the reinforcing rib 4 has a reinforcing rib lower flange 41, and the size of the processing area 31 matches the size of the reinforcing rib lower flange 41. Specifically, the lower surface of the rubber soft mold 3 has the same geometric profile as the upper surface of the skin process dummy 2, and the thickness of the rubber soft mold 3 is not less than the thickness of the reinforcing rib lower flange 41.

[0043] In one embodiment, the following steps are further included:

[0044] After the milling and cutting are completed, measure the processing area 31. If the size of the processing area 31 is within the error range, stop the processing. If the size of the processing area 31 is not within the error range, continue the milling and cutting until the size of the processing area 31 meets the error range.

[0045] In one embodiment, the error range includes: the dimensional error between the processing area 31 and the reinforcing rib lower flange 41 is not greater than ±0.25 mm, and the angular error is not greater than ±2°.

[0046] In one embodiment, both the first rubber layer and the second rubber layer are Airpad rubber, and the prepreg layer is a 2-8 layer carbon fiber prepreg ply or a 2-8 layer glass fiber prepreg ply.

[0047] In one embodiment, the skin forming mold 1 is provided with a skin process dummy positioning line and a laser positioning target hole.

[0048] In one embodiment, a laser positioning target is installed in the laser positioning target hole. The number M of the laser positioning targets ≥ 4, and the center distance H between two adjacent laser positioning targets ≤ 1 m.

[0049] In one embodiment, when using a laser tracker to emit positioning laser for positioning, the deviation of each laser positioning target from the positioning laser is not greater than 0.3 mm.

[0050] In one embodiment, the size of the processing area is 0.15 mm smaller than the size of the reinforcing rib lower flange. Leave an appropriate machining allowance, and then remove it manually later to ensure the smoothness of the milling section and the machining accuracy.

[0051] In one embodiment, the following steps are further included:

[0052] Manually mill and cut to remove the process allowance so that the size of the processing area is equal to the size of the reinforcing rib lower flange.

[0053] In one embodiment, a CVD composite coating milling cutter with a diameter of 4 mm is used to mill the machining area. The rotational speed of the milling cutter is 12,000 rad, the feed rate is 800 mm / min, and the cutting depth is not greater than 0.5 mm. By selecting a CVD composite coating milling cutter and appropriate machining parameters, the milling machining of the vulcanized rubber soft mold can be achieved.

[0054] The following is a specific embodiment provided by the present invention:

[0055] The length of the skin of a certain composite stiffened panel to be prepared is 10 m, the length of the ribs of the stiffeners is 7.5 m, the total number of stiffeners is 15, and the straightness requirement of the rib axes of the stiffeners is ±1 mm. A one-time co-curing forming scheme is adopted. Referring to Figures 1 - 4 , this example provides a method for preparing a co-curing forming soft mold, including the following steps:

[0056] Step 1: Prepare the skin process dummy 2. According to the skin structure in the digital model of the composite stiffened panel, design and manufacture the skin forming mold 1 using Q235 ordinary steel. The shaping surface of the skin forming mold 1 is equipped with 36 laser positioning target holes and 60 skin process dummy positioning lines. The skin process dummy positioning lines include 15 positioning lines in each of the front, back, left, and right directions. The center distance between adjacent laser positioning target holes is 0.8 m. Use the skin forming mold 1 to cure and prepare the skin process dummy 2 (composite material). Make positioning lines on the skin process dummy 2 according to the skin process dummy positioning lines on the skin forming mold 1. If the skin process dummy 2 undergoes a demolding process and then the rubber soft mold 3 is prepared again, the positioning of the skin process dummy 2 on the skin forming mold 1 can be completed first according to the positioning lines on the skin forming mold 1 and the skin process dummy 2; the skin process dummy 2 is not demolded after curing;

[0057] Step 2: Prepare the rubber soft mold 3. According to the digital model of the composite stiffened panel, design and prepare the rubber soft mold 3. The specific preparation method is as follows: Add 4 layers of carbon fiber prepreg between two layers of Airpad rubber. The above materials are laid, encapsulated, and vulcanized in a autoclave on the upper surface of the skin process dummy 2 to make the rubber soft mold as Figure 2 shown;

[0058] Step 3: Install the skin forming mold 1, the skin process dummy 2, and the vulcanized rubber soft mold 3 on the corresponding processing workbench;

[0059] Step 4: Determine the machining area 31 according to the position of the stiffener 4 in the digital model of the composite stiffened panel. Milling is carried out based on the contour of the area covered by the lower flange 41 of the stiffener (CNC milling area) to ensure the side angle of the lower flange 41 of the stiffener, and a CNC machining program is compiled. Among them, the cutting edge position of the milling machine is located inside the machining area 31; the unilateral dimension of the contour program of the machining area 31 is 0.15 mm smaller than the theoretical dimension; when programming, the height position from the skin process dummy 2 is not less than 1 mm, and a depth process allowance offset is set, leaving 1 mm of allowance as the process section; a CVD composite coating milling cutter with a size of 4 mm is selected, the rotational speed is S12000 rad, the feed rate is 800 mm / min, and the cutting depth is not greater than 0.5 mm;

[0060] Step 5: Use a laser tracker to pick up the laser positioning targets attached to the shaping surface of the skin forming die 1 for positioning. After positioning, use a five-axis CNC high-speed milling machine to mill and remove the area of the rubber soft mold 3 covered by the lower flange 41 of the stiffener in the digital model of the composite stiffened panel. After milling, use manual milling to remove the process amount to obtain the machining area 31, which is a machining groove corresponding to the shape and size of the lower flange 41 of the stiffener; when using a laser tracker for positioning, the deviation of each target point position is not greater than 0.3 mm; the tool length error is not greater than 0.02 mm; after milling, measurement is carried out, the dimension error is not greater than ±0.25 mm; the angle error is not greater than ±2°; use a wallpaper knife to manually cut 1 mm of process allowance, remove the redundant material and trim the burrs remaining after manual cutting to ensure that the fracture position of the rubber soft mold 3 fits the stiffener 4 after CNC milling as Figure 4 shown.

[0061] The present invention proposes a preparation method for a co-cured forming soft mold of a composite panel structure to ensure the dimensional accuracy of the rubber soft mold and the axis degree of the stiffeners of the composite stiffened panel, and at the same time cancel the production of stiffener process dummies (in the prior art, it is necessary to manufacture stiffener process dummies in advance and assemble and cure them with the laid-up rubber soft mold after cutting), reduce the repair work on the rubber soft mold after forming, improve the machining accuracy and production efficiency, and reduce the preparation cost. By improving the machining accuracy of the co-cured soft mold, the present invention solves the positioning problem of the stiffeners combined with the skin during the co-curing forming process of the composite panel structure, and ensures the axis accuracy of the ribs of the co-cured composite panel. For composite panel structures, especially large-size composite stiffened panel structures, it has certain engineering application value.

[0062] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite material wall panel structure co-curing soft mold, characterized in that: The following steps are involved: S1. Positioning, installing and curing the skin process dummy on the skin forming mold; S2, stacking and curing a rubber soft mold on the skinning process dummy, wherein the rubber soft mold includes a first rubber layer and a second rubber layer that are arranged opposite to each other, and a prepreg layer arranged between the first rubber layer and the second rubber layer; S3, clamping and fixing the skin forming mold, the skin process dummy and the rubber soft mold; S4. Milling the rubber soft mold to form a processing area, wherein the size of the processing area matches the size of the lower flange of the reinforcing rib.

2. The method for preparing a composite material wall panel structure co-curing soft mold according to claim 1, characterized in that: The following steps are also included: After milling is completed, the processing area is measured. If the size of the processing area is within the error range, the processing is stopped. If the size of the processing area is not within the error range, milling is continued until the size of the processing area meets the error range.

3. The method for preparing a composite material wall panel structure co-curing soft mold according to claim 2, characterized in that: The error range includes: the dimensional error between the processing area and the lower flange of the reinforcing rib is no more than ±0.25 mm, and the angular error is no more than ±2°.

4. The method for preparing a composite material wall panel structure co-curing soft mold according to claim 1, characterized in that: The first rubber layer and the second rubber layer are both Airpad rubber, and the prepreg layer is 2 to 8 layers of carbon fiber prepreg plies or 2 to 8 layers of glass fiber prepreg plies.

5. The method for preparing a composite material wall panel structure co-curing soft mold according to claim 4, characterized in that: The skin forming mold is provided with a skin process dummy positioning line and a laser positioning target hole.

6. The method for preparing a composite material wall panel structure co-curing soft mold according to claim 5, characterized in that: A laser positioning target is installed in the laser positioning target hole, the number of the laser positioning targets M is ≥ 4, and the center distance between two adjacent laser positioning targets is H ≤ 1 m.

7. The method for preparing a composite material wall panel structure co-curing soft mold according to claim 5, characterized in that: When using a laser tracker to emit a positioning laser for positioning, the point deviation between each laser positioning target and the positioning laser is no more than 0.3mm.

8. The method for preparing a composite material wall panel structure co-curing soft mold according to claim 1, characterized in that: The size of the processed area is 0.15 mm smaller than the size of the lower flange of the reinforcing rib.

9. The method for preparing a composite material wall panel structure co-curing soft mold according to claim 8, characterized in that: The following steps are also included: Manual milling is performed to remove process allowances so that the size of the processing area is equal to the size of the lower flange of the reinforcing rib.

10. The method for preparing a composite material wall panel structure co-curing soft mold according to claim 1, characterized in that: The processing area is milled using a 4 mm CVD composite material coated milling cutter, the rotation speed of the milling cutter is 12000 rad, the feed speed is 800 mm / min, and the cutting depth is not greater than 0.5 mm.

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