Evaluation of Testing Techniques for the losipescu Shear Test for Advanced Composite Materials

Abstract

The purpose of the study was to explore and subsequently establish ex perimental techniques for the losipescu shear test method for advanced composite materials. For the preparation of notches in the Iosipescu specimens it was found that con ventional machine cutting tools could be used provided that the base of the notch was in spected for micro-damage. The occurrence of a pure shear strain field in the test section was evaluated by separately monitoring the readings from the tension and compression strain gauges. Grinding of the four loading surfaces of the original University of Wyoming test fixture was required to eliminate in-plane or out-of-plane bending or twisting of the specimen. A state of pure shear strain (as defined by equal readings from the tension and compression gauges) can be produced in 90 degree but not 0 degree original Iosipescu specimens when tested in the original University of Wyoming fixture (when the loading surfaces were ground smooth and parallel). In terms of analysis of the results for the 90 degree specimens for IM6/1806, IM6/F584 and IM6/5245C material systems, the deter mination of the in-plane shear modulus by the tangent method had lower scatter than by initial modulus or secant methods.