Tensile dynamic behaviour of unidirectional glass fibre-reinforced thermoset matrix composites

Abstract
The aim of this study is to determine the tensile behaviour of unidirectional glass fibre-reinforced polyester matrix composites at high strain rate (≈ 10 ^-1). Different orientations of the composite are tested with an hydraulic tensile machine which covers the range from static strain rate to 50 s^-1. It is shown that difficulties might appear with solicitations of high velocity. The loading of the specimen becomes very complex. In this study, some improvements have been made to limit these effects. The geometry of the tests specimens is first optimised by a numerical simulation in order to obtain uniformly distributed stress and strain rate in the measurement zone. Another improvement is to choose an appropriate damping joint for limiting disturber loading. Displacement and force versus time signals obtained experimentally are free of oscillations. The longitudinal (0°) and transversal (90°) orientation of fibres in the composite are tested. For both orientation, it is observed that the mechanical properties (maximum stress, elastic modulus and failure strain) depend on the strain rate. Effect of the rate dependence on 0° specimens is moderate : the maximum stress increases slightly. For 90° specimens, the strain rate effect is much more significant on the maximum stress and the yield stress.