Self-tightening clamp for V-shaped notch shear test of composite material and test method

Abstract

The invention discloses a self-tightening clamp for a V-shaped notch shear test of a composite material. The self-tightening clamp comprises two clamping pieces which are oppositely arranged, each clamping piece comprises a body, the body comprises a clamping part and a stretching part which are connected together, the two ends of the clamping part form a connecting end and a clamping end, and the stretching part is connected to the connecting end; a stretching rod is mounted on the stretching part, and a positioning surface is formed on the side surface, facing the clamping end, of the stretching part; a wedge-shaped groove is formed in the clamping part, two wedge-shaped clamping blocks are movably mounted in the wedge-shaped groove, and a clamping groove is formed between the two wedge-shaped clamping blocks; a clamping groove is formed in the end, facing the stretching part, of each wedge-shaped clamping block, the adjusting plates are inserted into the clamping grooves, and the adjusting screw rods are connected to the adjusting plates. The invention further discloses a test method adopting the self-tightening clamp. By utilizing the device, the coincidence requirement of the central axis of the V-shaped notch section of the V-shaped notch sample and the load line can be effectively ensured, the testing efficiency is improved, and the sample mounting time and manpower are saved.

Description

technical field [0001] The invention relates to a self-tightening fixture and a test method for V-notch shear tests of composite materials, which can be used for V-notch shear performance tests of composite materials in engineering fields such as aviation, aerospace, wind power, and rail transit. Background technique [0002] At present, the main methods for testing the in-plane shear performance of composite materials are: torsion method, off-axis tensile method and shear method. The torsion method is a method based on the shear performance test of metal materials. It mainly generates pure shear stress on the thin-walled cylinder by applying torque to both ends of the thin-walled cylinder. However, due to the complicated sample preparation of this method, the test country During the process, the shear force caused by the torque of the clamping end makes it difficult for the sample to fail at the gauge length, the test results have large deviations, and an additional torsion...

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Problems solved by technology

[0004] ATSM D4255 specifies an orbital shear method, which generates shear loads by means of double-track tension or triple-track compression to determine in-plane shear performance, but the shear stress produced by it is not uniform

ASTM D5379 specifies an Iosipescu shear method, which applies a pair of loads of opposite directions and equal magnitude to the two ends of the notch of the sample by compression to generate shear stress at the gauge length of the sample, but this method is due to The working area is small, it is difficult to apply some thick fibers or fibers with large spacing

ASTM D7078 specifies a V-notch shear method, which is to apply tensile loads on both sides of the V-notch of the sample, thereby generating shear stress at the gauge length of the sample. The most important and common method for material shear performance, but testing according to the fixture recommended by ASTM D7078, is prone to the following problems: (1) The sample is fixed by screws on both sides of the fixture. Due to the difference in human operation, It is easy to cause the sample (9) to be twisted or misplaced in the fixture, so that the central axis of the V-shaped notch section cannot coincide with the load line, especially for samples with a size of about 2mm, which will have a greater impact on the results; (2) the whole set The clamp has 12 screws. In order to ensure the clamping of the sample, each screw needs to be tightened by slowly increasing the torque with a torque wrench, so the installation of the sample is time-consuming and laborious, and the efficiency is low

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