Shear Response ASTM D3518
In-plane shear response of polymer matrix composite materials, by tensile test of a ±45° laminate, per ASTM D-3518
ASTM D-3518 Shear is a test method used to measure the shear stress and shear strain properties of a composite material specimen composed of +45 plies and -45° plies. The physical properties of many materials can vary depending on ambient temperature, making it important to test materials at temperatures that simulate the intended end-use environment.
The test procedure for ASTM D-3518 involves placing test specimens in the grips of a universal tester at a specified grip separation and pulling until failure. The test specimens and protocol are as called out in ASTM D-3039 for Tensile Properties of Composite Materials. To measure strain response during the test, bonded strain gauges can be mounted to the specimen. A standard test speed of 2 mm/min is used for standard test specimens.
For elevated or reduced temperature testing, a thermal chamber is installed on the universal test machine. The chamber allows the test mounts to pass through the top and bottom, and standard test fixtures are installed inside the chamber. Testing is conducted inside the controlled thermal environment, the same as it would be at ambient temperature. The chamber has internal electric heaters for elevated temperatures and uses external carbon dioxide gas as a coolant for reduced temperatures.
The most common specimen size for ASTM D-3518 has a constant rectangular cross-section, 25 mm (1 in) wide and 250 mm (10 mm) long. Optional tabs can be bonded to the ends of the specimen to prevent gripping damage. The specimens can be machined from larger samples and tabs bonded if requested.
From the tensile test results, the following calculations can be made: Maximum Shear Strength, Shear Strain, Shear Modulus of Elasticity, and Offset Shear Strength. Testing under varying temperature conditions provides valuable information on the behavior of composite materials and helps to ensure their suitability for specific applications.