A non-destructive testing comparison test block for a composite material assembly structure and a manufacturing method thereof

Abstract

The present application discloses a non-destructive testing reference block for composite material assembly structure and a manufacturing method thereof. The non-destructive testing block is a double-layer structure of a composite material test piece + an aluminum alloy test piece, and is mechanically connected by Hi-Lok bolts and Hi-Lok nuts. 20 holes with a diameter of φ6.33 mm are made on the test block, and the hole positions are arranged at equal intervals. 13 cracks are prefabricated by electric spark machining at the edge of the holes in the aluminum alloy test piece. The prefabricated cracks are triangular, and the crack depths are designed as 0.5 mm, 1.0 mm, 2.0 mm and 3.0 mm. The crack lengths and crack depths are designed according to the proportional relationships of 0.5:1, 1:1, and 2:1 to simulate the fatigue cracks that may naturally occur at the edge of the assembly holes of the aircraft wing in actual work. The present application can simulate the cracks that may naturally occur at the edge of the holes of the aluminum alloy frame beam of the composite material wing assembly structure of the aircraft, and can be used for the verification research on the applicability of various non-destructive testing methods to the wing assembly structure, as well as the quantitative evaluation and analysis of the detection sensitivity. It can also be used for the verification of the effectiveness of the detection equipment, so as to ensure the product quality.

Description

Technical Field

[0001] This application belongs to the technical field of non-destructive testing, and more specifically, it relates to the technical field of non-destructive testing for assembly structures. Background Art

[0002] In modern aircraft wing design, the skin is generally made of carbon fiber composite materials, and generally there is an aluminum alloy frame beam under the skin. The skin and the aluminum alloy frame beam are mechanically assembled and connected by Hi-Lok bolts and Hi-Lok nuts. Such a structure can withstand high loads and is the development trend of wing structure types. For example, the latest developed Boeing B787 and Airbus A350 both adopt this structural form.

[0003] During the flight of an aircraft wing, due to the action of external loads generated by high-speed flight, large stress concentrations are likely to occur at the hole corner edge area of the connection holes, and then fatigue cracks will be generated. Once the fatigue cracks are generated, they will rapidly expand, which has a crucial impact on the safe flight of the aircraft. Therefore, it is necessary to regularly perform non-destructive testing (such as X-ray testing, eddy current testing, etc.) on the aircraft wing to ensure product quality. Whether the non-destructive testing method and testing equipment are reliable, especially whether they can detect the latent fatigue cracks at the hole corners of the aluminum alloy frame beam under the composite material skin of the wing structure, it is necessary to make a non-destructive testing comparison test block in advance and use this test block to verify the performance of the non-destructive testing method and testing equipment before each test. The artificial simulation of defects in the production of non-destructive testing comparison test blocks is a key technology, and the real simulation of fatigue cracks is the difficulty in the production of test blocks. Summary of the Invention

[0004] The technical problem to be solved by this application is to provide a comparison test block for non-destructive testing of composite material assembly structures, which can be used for the verification of various non-destructive testing methods and testing equipment, and can be repeatedly produced to ensure a high-quality level, so as to determine whether the non-destructive testing method and testing equipment are reliable; in addition, through the comparison of the detectability of prefabricated cracks of different sizes, it can be used for the comparison of the advantages and disadvantages of different non-destructive testing methods.

[0005] A comparison test block for non-destructive testing of composite material assembly structures in this application includes a composite material test piece and an aluminum alloy test piece. The composite material test piece and the aluminum alloy test piece are connected by Hi-Lok bolts; prefabricated cracks are provided at the edges of the holes connected by Hi-Lok bolts on the aluminum alloy test piece; the prefabricated cracks are triangular, the width of the cracks is in the range of 0.04 m to 0.09 m, the crack depths are set at 0.5 mm, 1.0 mm, 2.0 mm, and 3.0 mm, and the crack length to crack depth ratios are 0.5:1, 1:1, and 2:1; the holes connected by Hi-Lok bolts are arranged at equal intervals.

[0006] There are 20 Hi-Lok bolts for connection.

[0007] A total of 13 prefabricated cracks are provided.

[0008] The prefabricated cracks are arranged in a staggered manner, and the crack directions are randomly arranged to the left, right, and down.

[0009] The prefabricated cracks are prefabricated by electrical discharge machining.

[0010] The test block has an outer dimension of 164 mm in length, 98 mm in width, the composite material test piece has a thickness of 3 mm, and the aluminum alloy test piece has a thickness of 4 mm.

[0011] The aperture of the hole connected by the Hi-Lok bolt is 6.33 mm.

[0012] The manufacturing method of the non-destructive testing comparison test block for the composite material assembly structure of this application is as follows:

[0013] S1 Preparation of aluminum alloy test piece

[0014] Take an aluminum plate with a material of 7050-T7451-AMS4050H and a thickness of at least 6 mm, and perform milling and cutting to make a test piece with a thickness of 4 mm and drill holes;

[0015] S2 Prefabrication of cracks

[0016] Perform electrical discharge machining on the aluminum alloy test piece with drilled holes at the hole corner edge to prefabricate cracks.

[0017] S3 Measurement of crack size

[0018] Measure and inspect the crack length and crack width of the prefabricated cracks respectively, ensure that the maximum error of the crack length is controlled within ±5%, and the crack width is controlled within the range of 0.04 m to 0.09 m.

[0019] S4 Preparation of composite material test piece

[0020] Cut and stack the composite material prepreg cloth according to a size of not less than 200 mm × 120 mm, and send it to the autoclave for curing after stacking; after curing, perform numerical control milling on the prepared composite material laminate to prepare a composite material laminate with a size of 164 mm × 98 mm and a thickness of 3.0 mm; drill holes and countersink the composite material laminate, the drill hole diameter is 6.33 mm, and the maximum countersink diameter is 12.75 mm;

[0021] S5 Assembly of test block

[0022] Respectively press Figure 2 Mechanically connect the composite material test piece and the aluminum alloy test piece at each hole position with Hi-Lok bolts and Hi-Lok nuts to obtain a non-destructive testing test block for the composite material assembly structure.

[0023] A reference block for non-destructive testing of composite material assembly structures in the present application is a double-layer assembly connection structure of "composite material - aluminum". Artificial cracks with different lengths and depths are prefabricated at the edges of the assembly connection holes in the aluminum alloy layer by artificial methods. The prefabricated cracks are triangular, simulating the fatigue cracks that may naturally occur at the edges of the assembly holes of the aircraft wing during actual operation. There are 13 artificial defects in total. The outer dimensions of the block are 164 mm in length and 98 mm in width. The thickness of the composite material layer is 3 mm, and the thickness of the aluminum alloy layer is 4 mm. The cracks are arranged in a staggered manner, and the crack directions are randomly arranged to the left, right, and down.

[0024] The beneficial effects of the present application are as follows: Artificial cracks with different lengths, depths, and directions are prefabricated at the edges of the aluminum alloy assembly holes under the composite material skin. When detecting the fatigue cracks generated at the edges of the aluminum alloy frame beam assembly holes under the composite material skin of the aircraft wing assembly structure, it can be effectively used for verifying the applicability of the detection method and the detection sensitivity, and then can effectively screen out more suitable detection methods. Before each detection, this reference block can be used to verify the performance of the non-destructive testing method and testing equipment to ensure the reliability of the detection results. The reference block of the present application can be used for verifying the applicability of various non-destructive testing methods for detecting cracks in the aircraft wing assembly structure, as well as for quantitative evaluation and analysis of the detection sensitivity, and can also be used to verify the effectiveness of the testing equipment during actual operation, thereby ensuring the product quality. Brief Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the distribution of prefabricated cracks of a reference block for non-destructive testing of composite material assembly structures in the present application.

[0026] Figure 2 It is a schematic diagram of the crack cross-section.

[0027] Figure 3 It is a schematic diagram of the combined assembly relationship of a reference block for non-destructive testing of composite material assembly structures in the present application.

[0028] Figure 4 It is a three-dimensional schematic diagram of a reference block for non-destructive testing of composite material assembly structures in the present application. Detailed Embodiments

[0029] The present application will be further described below with reference to the accompanying drawings. Embodiment 1

[0030] A non-destructive testing comparison test block for a composite material assembly structure of the present application has an outer dimension of 164 mm in length, 98 mm in width, a thickness of 3 mm for the composite material test piece, and a thickness of 4 mm for the aluminum alloy test piece. A total of 20 holes with a diameter of φ6.33 mm are made in four rows and five columns at the same positions on the composite material test piece and the aluminum alloy test piece, and the hole positions are arranged at equal intervals. At the edges of the holes made in the aluminum alloy test piece, 13 cracks with different lengths and depths are prefabricated manually. The manually prefabricated cracks are triangular in shape to simulate the cracks that may occur naturally at the hole corners of the aluminum alloy frame beams in the aircraft composite wing assembly structure during actual operation. Example 2

[0031] A non-destructive testing comparison test block for a composite material assembly structure of the present application includes a composite material test piece 2 and an aluminum alloy test piece 1. The composite material test piece 2 and the aluminum alloy test piece 1 are connected by Hi-Lok bolts; prefabricated cracks are provided at the edges of the holes connected by the Hi-Lok bolts on the aluminum alloy test piece; the prefabricated cracks are triangular in shape, the width of the cracks is in the range of 0.04 m to 0.09 m, the crack depths are set at 0.5 mm, 1.0 mm, 2.0 mm, and 3.0 mm, and the crack lengths and crack depths are 0.5:1, 1:1, 2:1; the holes connected by the Hi-Lok bolts are arranged at equal intervals. There are 20 Hi-Lok bolts for connection. A total of 13 prefabricated cracks are provided. The prefabricated cracks are prefabricated by electric discharge machining. The outer dimension of the test block is 164 mm in length, 98 mm in width, the thickness of the composite material test piece is 3 mm, and the thickness of the aluminum alloy test piece is 4 mm. The aperture of the holes connected by the Hi-Lok bolts is 6.33 mm.

[0032] Figure 1 It is a schematic diagram of the defect arrangement, crack cross-section and test block outer shape of a comparison test block for non-destructive testing of an aircraft wing assembly structure of the present application. The hole numbers are represented by A1, A2, B1, B2,... as shown in the figure, and the length and depth are represented by X / Y (example: 0.5 / 2.0 represents a length of 0.5 mm and a depth of 2.0 mm). Example 3

[0033] The manufacturing method of a comparison test block for non-destructive testing of an aircraft wing assembly structure of the present application is as follows:

[0034] S1 Preparation of aluminum alloy test piece

[0035] The received material is an aluminum plate of 7050-T7451-AMS4050H with a thickness σ of at least 6 mm, and it is milled and processed as shown respectively to make a test piece with a thickness of δ4.0 mm and drill holes. Figure 1 shown respectively milled and processed to make a test piece with a thickness of δ4.0 mm and drill holes.

[0036] S2 Crack prefabrication

[0037] The pre-drilled S1 aluminum alloy test piece 1 is damaged by electrical discharge machining. The hole positions, directions, lengths, depths, and patterns of the damage are as follows Figure 1 shown. The hole numbers for drilling are represented by A1, A2, B1, B2,... as shown in the figure. The length and depth are represented by X / Y (example: 0.5 / 2.0 means a length of 0.5 mm and a depth of 2.0 mm).

[0038] S3 Crack Size Measurement

[0039] The prefabricated cracks are respectively measured for crack length and crack width. The measurement results show that the crack lengths prefabricated by the electrical discharge method are very accurate, and the maximum error is controlled within ±2%. The crack width is about 0.06, indicating that the cracks simulated and prefabricated by the electrical discharge method adopted in this application can more realistically represent fatigue cracks, with high manufacturing precision and can be fabricated repeatedly.

[0040]

[0041] S4 Preparation of Composite Material Test Pieces

[0042] The prepreg cloth of the composite material with the grade of T700 / LT-03A is cut and laminated according to a size of not less than 200 mm × 120 mm, and then sent to an autoclave for curing after lamination. After curing, the prepared composite laminate is numerically controlled milled to prepare a composite laminate with a size of 164 mm × 98 mm and a thickness of 3.0 mm. The prepared composite laminate 2 is Figure 1 drilled and counterbored at the positions shown. The drill hole diameter is 6.33 mm, and the maximum counterbore diameter is 12.75 mm.

[0043] S5 Test Block Assembly

[0044] Respectively according to Figure 3 and Figure 4 The holes of the composite material test piece 2 and the aluminum alloy test piece 1 are connected and assembled in combination with Hi-Lok bolts 4 and Hi-Lok nuts 3.

Claims

1. A non-destructive testing comparison test block for a composite material assembly structure, characterized in that, it includes a composite material test piece and an aluminum alloy test piece, and the composite material test piece and the aluminum alloy test piece are connected by Hi-Lok bolts; prefabricated cracks are provided at the edges of the holes connected by Hi-Lok bolts on the aluminum alloy test piece; the prefabricated cracks are triangular, the width of the cracks is in the range of 0.04 m to 0.09 m, the crack depths are set at 0.5 mm, 1.0 mm, 2.0 mm and 3.0 mm, and the crack lengths and crack depths are 0.5:1, 1:1, 2:1; the holes connected by Hi-Lok bolts are arranged at equal intervals, and the holes on the composite material test piece are countersunk holes.

2. The non-destructive testing comparison test block for a composite material assembly structure according to claim 1, characterized in that, 20 Hi-Lok bolts are provided for the connection.

3. The non-destructive testing comparison test block for a composite material assembly structure according to claim 1, characterized in that, a total of 13 prefabricated cracks are provided.

4. The non-destructive testing comparison test block for a composite material assembly structure according to claim 1, characterized in that, the prefabricated cracks are arranged in a staggered manner, and the crack directions are randomly arranged to the left, right and down respectively.

5. The non-destructive testing comparison test block for a composite material assembly structure according to claim 1, characterized in that, the prefabricated cracks are prefabricated by an electric discharge machining method.

6. The non-destructive testing comparison test block for a composite material assembly structure according to claim 1, characterized in that, the outer dimensions of the test block are 164 mm in length, 98 mm in width, the thickness of the composite material test piece is 3 mm, and the thickness of the aluminum alloy test piece is 4 mm.

7. The non-destructive testing comparison test block for a composite material assembly structure according to claim 1, characterized in that, the aperture of the holes connected by Hi-Lok bolts is 6.33 mm.

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