Method of protecting a rigid composite article from rain erosion

Abstract

The application discloses a rain-erosion-resistant protection method for rigid composite material parts and belongs to the technical field of composite material protection. In order to solve the problem that the rigid composite material parts are easily damaged by liquid drop impact in a rain-erosion scene, the method mainly removes a preset thickness of a rigid layer and spreads and lays a fiber-reinforced flexible composite material as a flexible layer, the flexible layer and the rigid layer are connected through in-situ curing of a flexible resin, and thus the overall protection performance is improved. The application can realize the synergistic effect of the rigid part bearing the load and the flexible part absorbing the impact energy, and the rain-erosion resistance, sand-erosion resistance and impact resistance of the parts are significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite material protection, and particularly relates to a rain erosion resistant protection method for rigid composite material parts. BACKGROUND

[0002] At present, in order to achieve the targets of wave penetration, stealth and light weight, a large number of quartz / glass fiber composite materials and carbon fiber composite material parts are used in aircraft wave penetration cabins, aerodynamic leading edges and wind power blade leading edges. With the further improvement of the tip speed and the improvement of the all-weather use demand, the defects of the rain erosion resistance of the composite material products are further exposed. In the case that the aircraft penetrates rain or cloud or the rotor part rotates at high speed in liquid drops, rain erosion occurs, which causes the matrix fragmentation and fiber fracture in the composite material and even structural damage, which is an important cause of damage in the service process of the composite material in the high-speed scene.

[0003] At present, in order to improve the rain erosion resistance of the high-speed scene composite material products, two main technical paths are adopted. One is to coat a flexible coating on the surface of the part, and the other is to paste a flexible film. The coating system adopted by the flexible coating includes neoprene, polyurethane and fluororubber coating, which is suitable for different temperature conditions. However, since the coating is in situ running on the surface of the part, and the coating system usually has no reinforcing body, the breaking strength and elongation of the coating material are poor, and the coating process is seriously dependent on the coating process. The flexible film is usually polyurethane film bonded by pressure-sensitive adhesive or hot melt adhesive. Since the polyurethane film is prepared separately, it can be strengthened by high pressure or bidirectional stretching, and the breaking strength and elongation rate can be increased by 100% to 150% compared with the coating material. However, the bonding interface strength of the pressure-sensitive adhesive or hot melt adhesive is poor, and the interface is damaged first under the condition of rain erosion, resulting in the bubbling or flaky peeling between the rain erosion protection film and the substrate. SUMMARY

[0004] The purpose of the present application is to provide a rain erosion resistant protection method for rigid composite material parts, which can greatly improve the rain erosion resistant performance of the rigid composite material parts by designing and adding a flexible layer on the rigid composite material parts.

[0005] The technical scheme adopted by the present application to achieve the purpose is as follows:

[0006] A rain erosion resistant protection method for rigid composite material parts, comprising the following steps:

[0007] Determining the to-be-protected area of the rigid composite material part, and removing the rigid layer of the area with a predetermined thickness;

[0008] Paving the fiber-reinforced flexible composite material on the to-be-protected area as a flexible layer, and connecting the flexible layer and the rigid layer by in-situ curing of the flexible resin to achieve rain erosion resistant protection.

[0009] Further, if the rigid layer of the rigid composite part originally contains a rain erosion protection layer, the fiber-reinforced flexible composite material is laid between the rain erosion protection layer and the rigid layer from which the preset thickness is removed, so that the flexible layer formed serves as an intermediate layer.

[0010] Further, the rigid composite part is a wave-transparent structure, a load-bearing structure, a fairing structure, a rotor structure, an impact-resistant structure, or a blast-resistant structure for a rain erosion scene.

[0011] Further, the fiber-reinforced flexible composite material includes one of a quartz fiber-reinforced polyurethane composite material, a carbon fiber-reinforced polyurea composite material, a glass fiber-reinforced polyurea composite material, a quartz fiber-reinforced polyurea composite material, a carbon fiber-reinforced silicone rubber composite material, and a carbon fiber-reinforced polysiloxane composite material.

[0012] Further, if the rigid layer of the rigid composite part is made of a quartz fiber-reinforced cyanate ester composite material, the flexible layer is made of a quartz fiber-reinforced polyurethane composite material.

[0013] Further, if the rigid layer of the rigid composite part is made of a carbon fiber-reinforced epoxy composite material, the flexible layer is made of a carbon fiber-reinforced polyurea composite material.

[0014] Further, if the rigid layer of the rigid composite part is made of an aramid / carbon fiber hybrid fabric-reinforced epoxy composite material, the flexible layer is made of a carbon fiber-reinforced silicone rubber composite material.

[0015] The present application has the following beneficial effects:

[0016] 1. The present application greatly improves the rain erosion protection performance of the part by designing and adding a fiber-reinforced flexible layer on the surface of the rigid composite part, which can effectively absorb liquid drop impact energy and buffer stress.

[0017] 2. The present application uses a flexible resin in-situ curing process, so that the bonding force between the flexible layer and the rigid layer is strong, and the structural stability and protection effect are significantly enhanced.

[0018] 3. The present application realizes the design of different material systems in the thickness direction of the product by optimizing the materials of the flexible layer and the rigid layer, and obtains a multifunctional structure layer with different stiffness and impact resistance.

[0019] 4. The present application is suitable for various harsh application scenes, such as rain erosion, sand erosion, bullet impact or blast, and other complex working conditions, and meets the needs of wave-transparent structures, load-bearing structures, impact-resistant structures, etc.

[0020] 5. The present application makes full use of the designability of composite materials, optimizes the balance of structural load bearing and rain erosion / sand erosion / impact resistance, and expands the potential application of composite materials in complex environments such as aircraft.

[0021] 6. The present application provides customized solutions for various specific scenarios through the rational combination of different materials, such as quartz fiber reinforced cyanate ester and polyurethane, carbon fiber reinforced epoxy resin and polyurea, etc., showing strong adaptability and practical value. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a rain erosion protection improvement schematic diagram of the leading edge of the aircraft fairing in Example 1.

[0023] Figure 2 is a rain erosion protection improvement schematic diagram of the leading edge of the fixed-wing unmanned aerial vehicle tail in Example 2.

[0024] Figure 3 is a rain erosion protection improvement schematic diagram of the antenna cover of the unmanned aerial vehicle in Example 3.

[0025] Figure 4 is a rain erosion protection improvement schematic diagram of the leading edge of the wind power blade in Example 4. DETAILED DESCRIPTION

[0026] In order to make the above technical features and advantages or technical effects of the technical scheme of the present application more obvious and easy to understand, the following will be described in detail with reference to the drawings.

[0027] Example 1

[0028] A certain civil aircraft fairing adopts a single-layer structure of glass fiber reinforced epoxy resin composite material, and its leading edge is damaged by rain erosion / sand erosion during service, with a standard rain erosion resistance life of 35 minutes. The present application is used for improvement, and 1 / 3 of the total thickness of the glass fiber reinforced epoxy resin composite material (i.e. rigid layer) at the leading edge is changed to glass fiber reinforced polyurea composite material as a flexible layer, forming a gradient composite material structure, as shown in Figure 1 .

[0029] The glass fiber reinforced polyurea composite material has dielectric properties close to those of the glass fiber reinforced epoxy composite material, and thus has little effect on the wave-penetrating property. The improved gradient composite material structure is subjected to rain erosion test, and under the same rainfall and flight speed, the rain erosion life of the improved structure reaches 140 min. Meanwhile, the improved gradient composite material structure is subjected to vibration, impact, bird strike, and aerodynamic load tests. Due to the damping effect of the flexible layer, the structure has smaller response under dynamic load such as vibration and impact, and the simulation deformation under aerodynamic load increases by 20% relative to the original state, and the simulation maximum stress increases by 25% relative to the original state, which are within the safe range. The improved gradient composite material structure is subjected to actual strength test, and the maximum deformation of the product under the limit load increases by 22% relative to the original state, and the maximum stress of the sampling point test increases by 24% relative to the original state, which are within the safe state.

[0030] Example 2

[0031] The leading edge of the tail wing of a certain civil fixed-wing unmanned aerial vehicle is made of a 3.0 mm thick carbon fiber reinforced epoxy resin composite material structure (i.e., a rigid layer), and a 0.36 mm flexible polyurethane film is originally attached to the surface as a rain erosion protective layer for improvement. Test shows that the improved structure appears delamination between the polyurethane film and the base material after about 90 min of standard rain erosion test. The original structure is improved by reducing the thickness of the 3.0 mm thick carbon fiber reinforced epoxy resin composite rigid layer of the leading edge part to 2.7 mm, adding a 0.5 mm thick carbon fiber reinforced polysiloxane composite material as a flexible layer, and then attaching a 0.36 mm flexible polyurethane film rain erosion protective layer (not shown in the figure) to the surface to form a gradient composite material structure, as shown in Figure 2 .

[0032] A flexible layer is added as a transition between the flexible polyurethane film and the rigid layer, providing load buffering during impact load. The improved gradient composite material structure is subjected to standard rain erosion test, and after 240 min, the flexible polyurethane film appears pitting and begins to expand and damage, but the interface does not damage. Meanwhile, the structure strength, fatigue, and vibration impact tests are carried out, and the structure safety and fatigue characteristics meet the design requirements.

[0033] Example 3

[0034] The antenna cover of a certain civil unmanned aerial vehicle adopts a honeycomb sandwich structure, and the outer skin is a quartz fiber reinforced epoxy resin composite structure with a thickness of 1 mm. During the flight test, it is found that after 5-7 takeoffs and landings in rainy weather, the outer skin begins to be damaged seriously and cannot continue to serve. The outer skin is improved by the method to a quartz fiber reinforced epoxy resin composite structure (i.e. rigid layer) with a thickness of 0.7 mm and a quartz fiber reinforced polyurea composite structure (i.e. flexible layer) with a thickness of 0.4 mm, forming a gradient composite structure, which can maintain the original structural strength and rigidity, as shown in Figure 3 .

[0035] The improved gradient composite structure is tested by flight test, and after 13-15 takeoffs and landings in rainy weather, the outer skin rigid layer is undamaged, and the flexible layer has cracks. However, the quartz fiber reinforced polyurea composite flexible layer can be prepared in situ after polishing and coated to continue to serve, which can prevent damage to the outer skin rigid layer. The electrical properties, structural strength and rigidity, and rain erosion resistance of the repaired product are not different from the original state.

[0036] Example 4

[0037] The blade of a certain type of wind power equipment has a working radius of 60 meters, a maximum rotating speed of 38 r / min, and a maximum tip speed of 120 m / s. The main structure of the blade is a foam core layer and a glass fiber epoxy resin composite skin structure (i.e. rigid layer), and the skin structure has a thickness of 8 mm. The surface is coated with a 1.2 mm thick coating as a rain erosion protective layer. Under the combined action of rain erosion / sand erosion / sunlight, etc. in the weather conditions at the installation location, the maintenance period is 1.5 years. The method is improved to maintain the thickness of the skin structure unchanged, and a glass fiber reinforced polyurea composite with a thickness of 0.5 mm is formed on the skin structure as a flexible layer structure, and a rain erosion protective layer with a thickness of 0.7 mm is coated on the flexible layer structure to form a gradient composite material, as shown in Figure 4 .

[0038] The total thickness of the improved gradient composite material structure is unchanged, and the increase in the thickness gradient does not exceed 2% of the total weight of the structure. Within the design tolerance, the environmental erosion resistance is significantly improved through equivalent tests and actual installation tests, and the maintenance period is increased to 2.5-3 years, which significantly improves the continuous operation time of the equipment and reduces the maintenance cost of the equipment.

[0039] Although the present application has been disclosed as above, it is not intended to limit the present application, and appropriate modifications or equivalent replacements of the technical solutions of the present application made by those skilled in the art should be covered within the protection scope of the present application, and the protection scope of the present application is defined by the claims.

Claims

1. A method of providing rain-erosion protection to a rigid composite article, the method comprising: The method comprises the following steps: determining a region to be protected of the rigid composite part, and removing a preset thickness of the rigid layer of the region; applying a fiber-reinforced flexible composite material to the region to be protected as a flexible layer, and connecting the flexible layer and the rigid layer by in-situ curing of flexible resin, so as to achieve rain erosion protection; the fiber-reinforced flexible composite material comprises one of a quartz fiber-reinforced polyurethane composite material, a carbon fiber-reinforced polyurea composite material, a glass fiber-reinforced polyurea composite material, a quartz fiber-reinforced polyurea composite material, a carbon fiber-reinforced silicone rubber composite material, and a carbon fiber-reinforced polysiloxane composite material.

2. The method of claim 1, wherein, If the rigid layer of the rigid composite part originally comprises a rain erosion protection layer, the fiber-reinforced flexible composite material is applied between the rain erosion protection layer and the rigid layer from which the preset thickness is removed, so that the flexible layer formed serves as an intermediate layer.

3. The method of claim 1, wherein, The rigid composite part is a wave-transparent structure, a load-bearing structure, a fairing structure, a rotor structure, an impact-resistant structure, or an anti-explosion structure used in a rain erosion environment.

4. The method of claim 1, wherein, If the rigid layer of the rigid composite part is made of a quartz fiber-reinforced cyanate ester composite material, the flexible layer is made of a quartz fiber-reinforced polyurethane composite material.

5. The method of claim 1, wherein, If the rigid layer of the rigid composite part is made of a carbon fiber-reinforced epoxy resin composite material, the flexible layer is made of a carbon fiber-reinforced polyurea composite material.

6. The method of claim 1, wherein, If the rigid layer of the rigid composite part is made of an aramid / carbon fiber hybrid fabric-reinforced epoxy resin composite material, the flexible layer is made of a carbon fiber-reinforced silicone rubber composite material.

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