The response to shock loading of a glass-fibre-epoxy composite: effects of fibre orientation to the loading axis

The shock response of a two-dimensional glass-fibre-epoxy composite has been investigated in terms of orientation of the fibres to the loading axis. Results show that when shocked in the through thickness orientation (fibres normal to the loading axis), the resultant shock pulses are similar to many other monolithic materials, and the shock velocity-particle velocity is linear. Examination of the spall response as a function of specimen thickness and the release velocities has also led us to suggest that the shock pulse generates damage behind it, which accumulates as a function of pulse duration. In contrast, when shocked along a fibre direction, the shock pulses have a strongly ramped nature, which steepens to a shock at higher stress amplitudes. Analysis of the wave velocity-particle velocity behaviour has led us to suggest that a low amplitude stress pulse is transmitted along the fibres, with the higher amplitude remainder being transmitted in the 'matrix'-i.e. the epoxy binder and fibres normal to the loading axis between them. Such a response has been observed in other fibre-based composites, and it is believed that this is due to the structural configuration of such materials.