Test device and test method for dynamic shear performance test of composite materials

Abstract

The present invention discloses a test device and a test method for dynamic shear performance test of composite materials. It belongs to the field of mechanical property test of materials. The device is composed of two upper and lower tensile clamping devices, which are coplanar and coaxially placed. The upper tensile clamping device includes an upper positioning groove clamp and an upper pressure block, and the lower tensile clamping device includes a lower positioning groove clamp and a lower pressure block. The upper pressure block and the lower pressure block are respectively installed on the upper positioning groove clamp and the lower positioning groove clamp by fastening bolts. Features of the present invention: The device has a simple structure, is easy to process and maintain, and can conveniently complete the test task; in addition, the shape of the specimen is easy to process and does not require a special processing shape; it can realize the dynamic shear load loading test of the material on a dynamic tensile testing machine, and the test cost is low; the test device has sufficient loading accuracy.

Description

Technical Field

[0001] The invention belongs to the field of material mechanical property testing, and relates to a test device and a test method for testing the dynamic shearing property of a composite material. Background Art

[0002] In the prior art, with the continuous development of aerospace technology and military equipment, the load forms that composite materials bear in their main structures are becoming more and more complex. Impact failure and shear failure are both common failure modes of materials. Therefore, the study of the dynamic mechanical properties of composite materials is becoming more and more necessary, especially for the study of the dynamic shear properties of composite laminates. The results can be used to study its dynamic damage mechanism to ensure the safety of the material structure in use.

[0003] At present, the basic performance testing technology of composite materials is relatively mature. Generally, a test piece with symmetrical V-shaped notches is clamped on a pair of special fixtures. The test machine performs tensile loading in one direction to generate shear stress in the working area of ​​the sample, and finally the sample is destroyed by shear. The common in-plane shear test standard for composite materials can be found in GB / T 28889-2012 (static tensile performance test), while there is no standard to follow for the dynamic shear test method of composite materials.

[0004] Research on the dynamic mechanical properties of composite materials mainly focuses on the tensile and compression analysis of materials. There are relatively mature experimental foundations for the tensile and compression dynamic mechanical properties tests. The tests are relatively easy to operate and the test results are relatively easy to obtain. However, the dynamic shear test of composite materials is more difficult to achieve. During the dynamic shear test, the stress generated by the tensile or compressive load must be small enough so that the material is in a shear state. The special fixture should have sufficient relative movement space to prevent collisions. However, it is difficult to achieve the dynamic shear test of composite materials with existing technical means. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a test device and a test method for testing the dynamic shear properties of composite materials.

[0006] Technical solution: The present invention discloses a test device for testing the dynamic shear performance of composite materials, which is composed of two matching upper and lower tensile clamping devices.

[0007] The upper stretching clamping device comprises an upper positioning groove clamp and an upper pressing block, wherein the upper pressing block is clamped in a groove formed in the upper positioning groove clamp;

[0008] A plurality of upper bolt holes are provided on the upper positioning groove clamp and the upper pressing block, and fastening bolts are passed through the upper bolt holes. The fastening bolts pass through the upper pressing block and the upper positioning groove clamp and are fixed by nuts.

[0009] The lower stretching clamping device comprises a lower positioning groove clamp and a lower pressing block, wherein the lower pressing block is clamped in a groove formed in the lower positioning groove clamp;

[0010] A plurality of lower bolt holes are provided on the lower positioning groove fixture and the lower pressing block, and fastening bolts are passed through the lower bolt holes. The fastening bolts pass through the lower pressing block and the lower positioning groove fixture and are fixed by nuts.

[0011] A groove is provided at the center of the upper end of the lower stretching clamping device, and an upper stretching clamping device matching with the lower stretching clamping device is installed in the groove;

[0012] A test piece is also installed between the upper positioning groove fixture, the lower positioning groove fixture, the upper pressing block, and the lower pressing block;

[0013] A bolt hole is provided on the test piece;

[0014] The number of the upper bolt holes is 6, and the upper pressing block is mounted on the upper positioning groove fixture by means of 6 fastening bolts passing through the upper bolt holes;

[0015] The number of the lower bolt holes is 8, and the lower pressing block is mounted on the lower positioning groove fixture by means of 8 fastening bolts passing through the lower bolt holes;

[0016] The inner planes of the upper positioning groove clamp and the upper pressing block are embossed, and an upper clamping end is installed on the top of the upper positioning groove clamp;

[0017] The inner planes of the lower positioning groove fixture and the lower pressing block are embossed, and a lower loading end is arranged at the bottom of the lower positioning groove fixture;

[0018] The width of the grooves in the upper positioning groove fixture and the lower positioning groove fixture is equal to the width of the test piece, both of which are D, and when the upper tensile clamping device and the lower tensile clamping device are placed in the initial position, there is a gap with a width of d on both sides;

[0019] The operation steps are as follows:

[0020] (1) Prepare a plane shear material test piece with a width of D, and spray a speckle pattern on the surface of the test piece to measure the surface strain of the test piece during the test;

[0021] (2) Place the upper positioning groove fixture and the lower positioning groove fixture in the initial position so that the positioning grooves are coplanar, and install the test piece in the opened grooves, align them, and then drill holes;

[0022] (3) Install the upper pressing block on the upper positioning groove fixture by using 6 fastening bolts; install the lower pressing block on the lower positioning groove fixture by using 8 fastening bolts;

[0023] (4) Operate the upper and lower chucks of the dynamic tensile testing machine to clamp the upper positioning groove fixture and the lower positioning groove fixture respectively, set the loading rate according to the material properties, and start the test until the test piece is destroyed.

[0024] The working principle of the present invention is: the dynamic tensile testing machine applies a dynamic tensile load at the clamping end until the test piece is destroyed, and the shear load can be obtained as F. Then the approximate calculation formulas of the shear stress τ and the shear strain γ of the material are respectively:

[0025] τ=F / D,γ=x / d,

[0026] Where x is the relative displacement of the test piece surface measured by digital speckle technology.

[0027] Beneficial effects: Compared with the prior art, the present invention has the following features: 1. The device has a simple structure, is easy to process and maintain, and can conveniently complete the test task; 2. The sample shape is easy to process, and no special processing shape is required; 3. The dynamic shear load loading test of the material can be realized on a dynamic tensile testing machine, and the test cost is low; 4. The test device has sufficient loading accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the structure of the present invention;

[0029] Figure 2 It is a front view of the present invention;

[0030] Figure 3 It is a loading schematic diagram when the present invention is working;

[0031] In the figure, 1 is an upper positioning groove fixture, 2 is an upper pressure block, 3 is a fastening bolt, 4 is a test piece, 5 is a lower pressure block, and 6 is a lower positioning groove fixture. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the technical solution of the present invention, the technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0033] As shown in the figure, the test device for dynamic shear performance test of composite materials described in the present invention is composed of two matching upper and lower tensile clamping devices.

[0034] The upper stretching clamping device comprises an upper positioning groove clamp 1 and an upper pressing block 2, wherein the upper pressing block 2 is clamped in a groove formed in the upper positioning groove clamp 1;

[0035] A plurality of upper bolt holes are provided on the upper positioning groove clamp 1 and the upper pressing block 2, and fastening bolts 3 are passed through the upper bolt holes. The fastening bolts 3 pass through the upper pressing block 2 and the upper positioning groove clamp 1 and are fixed by nuts.

[0036] The lower stretching clamping device comprises a lower positioning groove fixture 6 and a lower pressing block 5, wherein the lower pressing block 5 is clamped in a groove formed in the lower positioning groove fixture 6;

[0037] A plurality of lower bolt holes are provided on the lower positioning groove fixture 6 and the lower pressing block 5, and fastening bolts 3 are passed through the lower bolt holes. The fastening bolts 3 pass through the lower pressing block 5 and the lower positioning groove fixture 6 and are fixed by nuts.

[0038] A groove is provided at the center of the upper end of the lower stretching clamping device, and an upper stretching clamping device matching with the lower stretching clamping device is installed in the groove;

[0039] A test piece 4 is also installed between the upper positioning groove fixture 1, the lower positioning groove fixture 6 and the upper pressing block 2, the lower pressing block 5;

[0040] A bolt hole is provided on the test piece 4;

[0041] The number of the upper bolt holes is 6, and the upper pressing block 2 is installed on the upper positioning groove fixture 1 through 6 fastening bolts 3 passing through the upper bolt holes;

[0042] The number of the lower bolt holes is 8, and the lower pressing block 5 is installed on the lower positioning groove fixture 6 through 8 fastening bolts 3 passing through the lower bolt holes;

[0043] The inner planes of the upper positioning groove fixture 1 and the upper pressing block 2 are embossed, and an upper clamping end is installed on the top of the upper positioning groove fixture 1;

[0044] The inner planes of the lower positioning groove fixture 6 and the lower pressing block 5 are embossed, and a lower loading end is installed at the bottom of the lower positioning groove fixture 6;

[0045] The groove widths in the upper positioning groove fixture 1 and the lower positioning groove fixture 6 are equal to the width of the test piece 4, both of which are D, and when the upper tensile clamping device and the lower tensile clamping device are placed in the initial position, there are gaps with a width of d on both sides;

[0046] The operation steps are as follows:

[0047] (1) preparing a plane shear material test piece 4 with a width of D, and spraying speckles on the surface of the test piece 4 for measuring the surface strain of the test piece 4 during the test;

[0048] (2) Place the upper positioning groove fixture 1 and the lower positioning groove fixture 6 at the initial position so that the positioning grooves are coplanar, and install the test piece 4 in the opened grooves, align them, and then perform drilling;

[0049] (3) Install the upper pressing block 2 on the upper positioning groove fixture 1 by using 6 fastening bolts 3; install the lower pressing block 5 on the lower positioning groove fixture 6 by using 8 fastening bolts 3;

[0050] (4) Operate the upper and lower chucks of the dynamic tensile testing machine to clamp the upper positioning groove fixture 1 and the lower positioning groove fixture 6 respectively, set the loading rate according to the material properties, and start the test until the test piece 4 is destroyed.

[0051] Example

[0052] A plane shear test piece of carbon fiber laminate material is prepared, and its width is D, and speckles are sprayed on the surface of the test piece, so that during the experiment, the strain of the test piece surface exposed between the gap of width d between the upper and lower positioning groove clamps can be measured; then, the upper positioning groove clamp 1 and the lower positioning groove clamp 6 are placed in the initial position so that the positioning grooves are coplanar, and the test piece 4 is installed in the opened grooves, and holes are punched after alignment; the upper pressing block 2 is installed on the upper positioning groove clamp 1 by 6 fastening bolts 3; the lower pressing block 5 is installed on the lower positioning groove clamp 6 by 8 fastening bolts 3, and the plane shear test piece is accurately installed in the test device; the test device is stretched by the test machine, and a shear load can be applied to the test piece, which is the same as the conventional dynamic tensile test operation, and the upper and lower chucks of the dynamic tensile test machine are operated to clamp the upper positioning groove clamp 1 and the lower positioning groove clamp 6 respectively, and the loading rate is set to start the test until the test piece 4 is destroyed.

[0053] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A test method for a test device for testing dynamic shear properties of composite materials, characterized in that: It is composed of two matching upper and lower stretching clamping devices; The upper stretching clamping device comprises an upper positioning groove clamp and an upper pressing block, and a plurality of upper bolt holes are provided on the upper positioning groove clamp and the upper pressing block, and fastening bolts are passed through the upper bolt holes; The lower stretching clamping device comprises a lower positioning groove clamp and a lower pressing block, and a plurality of lower bolt holes are provided on the lower positioning groove clamp and the lower pressing block, and fastening bolts are passed through the lower bolt holes. A test piece is installed between the upper positioning groove fixture, the lower positioning groove fixture, the upper pressing block and the lower pressing block; The width of the grooves in the upper positioning groove fixture and the lower positioning groove fixture is equal to the width of the test piece, both of which are D, and when the upper tensile clamping device and the lower tensile clamping device are placed in the initial position, there is a gap with a width of d on both sides; Specifically, a plane shear test piece of a carbon fiber laminate is prepared, and its width is D. Speckles are sprayed on the surface of the test piece, and then during the experiment, the strain of the test piece surface exposed between the gap of width d between the upper and lower positioning groove fixtures is measured; then, the upper positioning groove fixture and the lower positioning groove fixture are placed at the initial position, so that the positioning grooves are coplanar, and the test piece is installed in the opened groove, and holes are punched after alignment; The upper pressing block is installed on the upper positioning groove fixture by 6 fastening bolts; the lower pressing block is installed on the lower positioning groove fixture by 8 fastening bolts, and the plane shear test piece is accurately installed in the test device; the test device is stretched by the testing machine to apply a shear load to the test piece, and the upper and lower chucks of the dynamic tensile testing machine are operated to clamp the upper positioning groove fixture and the lower positioning groove fixture respectively, the loading rate is set, and the test is started until the test piece is destroyed.

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