Constant strain rate testing of a G10 laminate composite through optimized Kolsky bar pulse-shaping techniques

Abstract

Pulse-shaping techniques have been used for many years now in Kolsky bar testing of brittle materials. The use of pulse shapers allow the experimentalist to conduct high strain rate tests on brittle materials while ensuring that the sample will achieve a state of dynamic stress equilibrium before it fails, as well as to achieve a constant strain rate loading state for a large portion of the test. The process of choosing the appropriate pulse-shaper system has typically been one of trail-and-error, sometimes requiring many experimental trails to achieve optimal results. Advances in analytic modeling of Kolsky bar tests now make it possible, in an a priori fashion, to design a pulse-shaper system to produce a known constant strain rate experiment. This article describes the approach of coupling these analytic models to an optimization technique to quickly find a pulse-shaper system that will produce an experiment at a known constant strain rate. Experiments were conducted and the model predictions compared to resulting strain rate histories for a G10 material. Stress–strain curves for G10 are presented at three different strain rates in both the in-plane and out-of-plane loading configurations with respect to the laminate plys. The G10 material is not found to be rate sensitive in either its strength or failure properties.