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

The aim of this study is to determine the tensile behaviour of unidirection al glass fibre-reinforced polyester matrix composites at high strain Tate ( approximate to 10 s(-1)). Different orientations of the composite are teste d with an hydraulic tensile machine which covers the range from static stra in rate to 50 s(-1). It is shown that difficulties might appear with solici tations of high velocity. The loading of the specimen becomes very complex. In this study, some improvements have been made to limit these effects. Th e geometry of the tests specimens is first optimised by a numerical simulat ion in order to obtain uniformly distributed stress and strain rate in the measurement zone. Another improvement is to choose an appropriate damping j oint for limiting disturber loading. Displacement and force versus time sig nals obtained experimentally are free of oscillations. The longitudinal (0 degrees) and transversal (90 degrees) orientation of fibres in the composit e are tested For both orientation, it is observed that the mechanical prope rties (maximum stress, elastic modulus and failure strain) depend on the st rain rate. Effect of the rate dependence on 0 degrees specimens is moderate : the maximum stress increases slightly. For 90 degrees specimens, the str ain rate effect is much more significant on the maximum stress and the yiel d stress.