A method of forming a fluid passage in a composite aircraft stiffened panel

Abstract

The present application belongs to composite material forming technology, and relates to a forming method of an oil hole of an aircraft composite material stiffened panel. The present application effectively improves the efficiency and quality of manufacturing the oil hole of the composite material stiffened panel, solves the problem that the tool for drilling the oil hole interferes with the product, the product forming and the oil hole forming are completed at the same time, the working hours for separately processing the hole are saved, and the defects and problems of the mechanical processing of the composite material are avoided. The forming mechanism of the present application is simple, the positioning precision is high, the packaging of the vacuum bag during the forming process and the demolding of the product after the forming are facilitated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite material forming, and relates to a forming method of an oil passage hole of an aircraft composite material stiffened panel. BACKGROUND

[0002] With the application of integrated composite structures in the main load-bearing structure of an aircraft, composite material stiffened panels face new design requirements. In addition to meeting the structural strength and fatigue survivability requirements, the composite material partial functional area structure also needs to meet the use requirements such as oil supply, sealing, and oil passage. The design of the oil passage hole is an important measure to ensure oil passage and reduce unusable oil. The composite material stiffened panel is part of the structure, and the oil passage hole is usually arranged at the root of the composite material panel rib.

[0003] The technical problem to be solved by the present application is:

[0004] With the application of integrated composite structures in the main load-bearing structure of an aircraft, composite material stiffened panels face new design requirements. The present application provides a forming method of an oil passage hole of a composite material stiffened panel, which solves the following four problems.

[0005] (1) High design and manufacturing risk and great difficulty. Due to high modularity, the design and manufacturing of integrated composite structures bear greater risk than traditional metals. The design of large integrated composite materials is complex, difficult to prepare, and has many process steps. Any problem in any step may affect the overall performance. Therefore, higher safety margin should be considered in design, and more advanced process measures should be taken in manufacturing to ensure product quality.

[0006] (2) High maintenance requirement. The partial functional area structure is an important part of the aircraft. The oil tank area is usually equipped with oil supply system, oil pump, oil quantity sensor and other equipment, and the maintenance requirement is high.

[0007] (3) Existence of unusable oil. When the fuel system transports fuel, it is impossible to transport every drop of oil in the oil tank area to the engine for consumption. Therefore, a small amount of fuel cannot be used, which is called unusable oil. The weight of the unusable oil in the oil tank is largely determined by the height of the oil passage hole in the oil tank. Therefore, the shape and quality of the oil passage hole of the oil tank can reduce the amount of unusable oil, which is of great benefit to the performance and efficiency of the entire aircraft.

[0008] (4) The position of the oil passage hole is generally narrow, and the operation space is limited after curing and drilling. The design and manufacture of special tools are difficult, and the feeding speed and feeding force of the processing device are difficult to keep stable, which makes the product prone to defects such as porosity, delamination, tearing, burr and other defects, seriously affecting the performance and reliability of the composite material panel. SUMMARY

[0009] The purpose of this invention is to provide a simple molding process with controllable oil passage quality, enabling the one-time molding of reinforced composite material parts with oil passages that meet design requirements. It is applicable to various reinforced composite material panels with rib cross-sections such as "L", "T", "I", "J", "C", or "Z" shapes, and the oil passage shape can be round or irregular. A typical reinforced composite material panel with oil passages is shown below. Figure 1 As shown, Figure 1 Example of a reinforced wall panel for an "I"-shaped truss. Figure 2 This is an example of a common oil passage hole.

[0010] The technical solution of this invention:

[0011] A method for forming oil passage holes in a reinforced composite panel for aircraft, comprising the following steps:

[0012] The composite material reinforced wall panel is an "L-shaped", "T-shaped", "I-shaped", "J-shaped", "C-shaped" or "Z-shaped" stringer reinforced wall panel. The oil passage hole shape can be round or irregular hole, including the following steps:

[0013] Step 1: Skin preparation: First, lay the skin blank layer by layer on the skin curing mold. The skin can be pre-cured or bonded and cured at the same time as the stringer.

[0014] Step 2: Laying and Combining the Long Truss: Laying the long string blanks on the long string forming mold, and setting an oil passage hole forming device on the long string forming mold of the composite material reinforced wall panel. The custom-made pin is made of polytetrafluoroethylene material. The cross section of the pin is the same as that of the oil passage hole, which has a certain degree of elasticity. It coordinates the incompatibility between the mold and the product during the curing process and avoids damage to the parts by rigid materials. The material of this device is easy to obtain and the processing method is simple. It is a consumable item. After each use, it can be pulled out from the rib mold and replaced with a new part to quickly make it ready for use. Each layer of blank is pre-made with oil passage holes, which correspond to the oil passage hole device on the long string forming mold.

[0015] Figure 3 shows a schematic diagram of a typical composite material reinforced wall panel oil passage forming die. The dimensions of the PTFE plastic pin of the reinforcing strip core mold and the tooling core mold are as follows. Figure 4 As shown, the cross-section of the pin is the same as that of the oil passage hole, the thickness of the vertical edge of the rib is t, the length of the plastic pin is t + 2l1, l1 > t, and the depth of the core mold hole of the rib is reserved on each side as l2, which is generally 1 to 2 mm.

[0016] Assemble the various parts of the stringer, and if necessary, perform hot compaction to ensure that the thickness of each part of the stringer is similar to the thickness after curing, thus ensuring accurate positioning after assembly.

[0017] Step 3: Positioning and sealing of stringers and skin: Grind and clean the cured surfaces to be bonded as needed. Place a layer of adhesive film on the horizontal surface of the stringer to be bonded to the skin. Place and position the stringers according to their respective positions. Place auxiliary materials such as peelable protective layer, release film, and breathable felt. Stick sealing strips around the perimeter of the skin curing mold. Seal the entire part in a vacuum bag and check the airtightness.

[0018] Step 4: Curing: According to the corresponding material curing system, vacuuming, heating, and pressurizing are carried out to cure and shape the material.

[0019] Step 5: Cleaning and Demolding: After curing, remove the vacuum bag and auxiliary materials, remove the stringer core mold, and remove the custom PTFE pins.

[0020] The method is also applicable to the first curing of the stringer, followed by co-curing or secondary bonding with the skin.

[0021] The skin is either uncured or cured.

[0022] The method is applicable to composite material reinforced wall panels that are “L-shaped”, “T”-shaped, “I”-shaped, “J”-shaped, “C”-shaped or “Z”-shaped stringer reinforced wall panels.

[0023] The shape of the oil passage hole is suitable for round holes or irregularly shaped holes.

[0024] Beneficial effects:

[0025] The forming method provided by this invention effectively improves the efficiency and quality of manufacturing oil passage holes in reinforced composite wall panels. It solves the problem of interference between the drilling tools used for oil passage hole machining and the product, preventing machining. Product forming and oil passage hole forming are completed simultaneously, saving time spent machining the holes separately and avoiding defects and problems in composite material machining. The forming mechanism of this invention is simple, has high positioning accuracy, and facilitates vacuum bag sealing during the forming process and demolding of the formed product. Attached Figure Description

[0026] Figure 1 Schematic diagram of oil passage holes in composite reinforced wall panel;

[0027] Figure 2 Schematic diagram of oil passage holes (circular and irregular shapes);

[0028] Figure 3(a) is a schematic diagram of a one-time forming mold for oil passage holes in a composite reinforced wall panel;

[0029] Figure 3(b) is a cross-sectional view of the mold for forming the oil passage hole of the composite material reinforced wall panel in one step;

[0030] Figure 4 Schematic diagram of the tooling dimensions for the oil passage hole;

[0031] Figure 5 A schematic diagram of the I-shaped composite material reinforcement layer combination;

[0032] Figure 6 A schematic diagram of the composite material reinforcement strips with oil passage holes;

[0033] Figure 7 This is a schematic diagram showing the dimensions of a specific example.

[0034] In the diagram: 1. Skin; 2. Ribs; 3. Oil passage hole; 4. Core mold; 5. Top cover plate. Detailed Implementation

[0035] The invention will be further described below through specific operational examples to clarify the operational process.

[0036] Example 1:

[0037] Taking an "I"-shaped stiffened composite wall panel as an example, a circular oil passage hole 3 with a diameter of 6-10 mm is provided at the root of the stiffener 2. The distance between the hole axis and the upper surface of the horizontal edge of the stiffener 2 is 5-8 mm. A typical structure of the oil passage hole 3 in a composite stiffened wall panel is shown below. Figure 1 Since the distance between the axis of the oil passage hole 3 and the upper surface of the horizontal edge of the rib 2 is very small, the traditional machining method for making holes has certain limitations. Due to the size limitations of the tools, the drill bit clamping device interferes with the horizontal edge of the rib 2. The method of making holes from one side with a long drill bit is only suitable when all holes are coaxial and the distance between the hole at the center of the wall panel and the edge of the wall panel is less than the length of the drill bit.

[0038] A schematic diagram of the I-shaped composite material rib 2-layer ply combination is shown below. Figure 5 , 6 As shown, PTFE plastic pins are placed on the core mold 4 tooling, corresponding holes are pre-drilled on the layup, and then directly laid onto the two core molds 4 for assembly, encapsulation and curing.

[0039] Step 1: Place the PTFE plastic pin into the hole of the metal core mold 4 of the rib 2;

[0040] Step 2: When making the cut pieces, pre-make the oil passage hole 3 position;

[0041] Step 3: Lay the cut pieces onto the metal core mold 4 to form a C-shaped blank;

[0042] Step 4: Make the R-angle fiber strips and the upper and lower layer assemblies, and set them aside for later use;

[0043] Step 5: Assemble the components, encapsulate, and solidify.

[0044] Step 6: Remove the vacuum bag, remove the reinforcing strip 2 and core mold 4, and remove the plastic pin;

[0045] Step 7: Trim the surface of the parts and perform internal quality and external shape inspection.

[0046] Example 2:

[0047] A method for forming oil passage holes in a reinforced composite panel for aircraft, comprising the following steps:

[0048] The composite material reinforced wall panel is an "L-shaped", "T-shaped", "I-shaped", "J-shaped", "C" or "Z-shaped" stringer reinforced wall panel. The oil passage hole 3 can be round or irregularly shaped. The process includes the following steps:

[0049] Step 1: Skin preparation: First, lay the skin 1 blank layer by layer on the skin 1 curing mold. Skin 1 can be pre-cured or bonded and cured at the same time as the stringer.

[0050] Step 2: Laying and Combining the Long Truss: Laying the long string blanks on the long string forming mold, and setting the oil hole 3 forming device on the long string forming mold of the composite material reinforced wall panel. The custom-made pin is made of polytetrafluoroethylene material. The cross section of the pin is the same as that of the oil hole 3, which has a certain degree of elasticity. It coordinates the incompatibility between the mold and the product during the curing process and avoids damage to the parts by rigid materials. The material of this device is easy to obtain and the processing method is simple. It is a consumable item. After each use, it is pulled out from the rib 2 mold and replaced with a new part to quickly make it ready for use. Each layer of blank is pre-made with oil holes 3, which correspond to the oil hole 3 device on the long string forming mold.

[0051] Figure 3 shows a schematic diagram of a one-time forming mold for the oil passage hole 3 of a typical composite material reinforced wall panel. The dimensions of the reinforcing bar 2, the core mold 4, the PTFE plastic pin, and the tooling core mold 4 are as follows. Figure 4 As shown, the cross-section of the pin is the same as that of the oil passage hole 3, the thickness of the vertical side of the rib 2 is t, the length of the plastic pin is t + 2l1, l1 > t, and the depth of the core mold 4 hole of the rib 2 is reserved on each side with l2, which is generally 1 to 2 mm.

[0052] Assemble the various parts of the stringer, and if necessary, perform hot compaction to ensure that the thickness of each part of the stringer is similar to the thickness after curing, thus ensuring accurate positioning after assembly.

[0053] Step 3: Positioning and sealing of stringers and skin 1: Grind and clean the cured surfaces to be bonded as needed. Place a layer of adhesive film on the horizontal surface of the stringer that will be bonded to skin 1. Place and position the stringers according to their respective positions. Place auxiliary materials such as peelable protective layer, release film, and breathable felt. Stick sealing strips around the perimeter of the cured mold of skin 1. Seal the entire part in a vacuum bag and check for airtightness.

[0054] Step 4: Curing: According to the corresponding material curing system, vacuuming, heating, and pressurizing are carried out to cure and shape the material.

[0055] Step 5: Cleaning and Demolding: After curing, remove the vacuum bag and auxiliary materials, remove the stringer core mold 4, and remove the custom PTFE material pins.

[0056] The method is also applicable to curing the stringer first, and then bonding it to the skin 1 for co-curing or secondary bonding.

[0057] The skin 1 is either uncured or cured.

[0058] The method is applicable to composite material reinforced wall panels that are “L-shaped”, “T”-shaped, “I”-shaped, “J”-shaped, “C”-shaped or “Z”-shaped stringer reinforced wall panels.

[0059] The shape of the oil passage 3 is suitable for round holes or irregularly shaped holes.

Claims

1. A method for forming oil passage holes in a reinforced composite panel for aircraft, characterized in that, The steps are as follows: Step 1: Skin preparation: First, lay the skin (1) blank layer by layer on the skin (1) curing mold. The skin (1) is pre-cured or bonded and cured at the same time with the stringer. Step 2: Laying and combining stringers: Laying stringer blanks on stringer forming mold, setting oil hole (3) forming device on composite material reinforced wall panel stringer forming mold, using polytetrafluoroethylene material to customize pins, the cross section of which is the same as the cross section of oil hole (3), and has elasticity. After each use, it is pulled out from the stiffener (2) mold, and a new part can be replaced to quickly meet the usage conditions. Each layer of blank is prefabricated with oil hole (3), which corresponds to the oil hole (3) device on stringer forming mold; The cross-section of the pin is the same as that of the oil passage hole (3). The thickness of the vertical side of the rib (2) is t. The length of the plastic pin is t + 2l1, where l1 > t. The hole depth of the core mold (4) of the rib (2) is reserved on each side by l2. Step 3: Positioning and sealing of stringers and skin (1): Grind and clean the cured surfaces to be bonded as needed. Place a layer of adhesive film on the horizontal surface of the stringer that is to be bonded to the skin (1). Place and position the stringers according to their positions. Place a peelable protective layer, a release film, and a breathable felt. Stick sealing strips around the curing mold of the skin (1). Seal the entire part with a vacuum bag and check the airtightness. Step 4: Curing: According to the corresponding material curing regime, vacuuming, heating, and pressurizing are performed to cure and shape the material; Step 5: Cleaning and demolding: After curing, remove the vacuum bag and auxiliary materials, remove the stringer core mold (4), and remove the custom pins made of polytetrafluoroethylene material.

2. The method for forming oil passages in a reinforced composite material panel for aircraft as described in claim 1, characterized in that, The skin (1) is either uncured or cured.

3. A method for forming oil passages in a reinforced composite material panel for aircraft as described in claim 1 or 2, characterized in that, The method described is applicable to composite material stiffened wall panels that are "L-shaped", "T-shaped", "I-shaped", "J-shaped", "C-shaped" or "Z-shaped" stringer stiffened wall panels.

4. A method for forming oil passages in a reinforced composite material panel for aircraft as described in claim 1 or 2, characterized in that, The shape of the oil passage (3) is suitable for round holes or irregular holes.

5. A method for forming oil passages in a reinforced composite material panel for aircraft as described in claim 1 or 2, characterized in that, The l2 mentioned is 1~2mm.

6. The method for forming oil passages in a reinforced composite material panel for aircraft as described in claim 3, characterized in that, The l2 mentioned is 1~2mm.

7. The method for forming oil passages in a reinforced composite material panel for aircraft as described in claim 4, characterized in that, The l2 mentioned is 1~2mm.

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