ASPECTS OF DYNAMIC MECHANICAL ANALYSIS IN POLYMERIC COMPOSITES

Patterns of behaviour of dynamic mechanical properties in the glass-transition region have been considered and it is shown that the tan delta peak always occurs at a higher temperature than the E'' peak. The temperature interval between the peaks varies significantly in unidirectional carbon-fibre/epoxy laminates, depending on the fibre orientation with respect to the applied load. The E'' peak is shown to be a more consistent indicator of the behaviour of the composites. Fibre incorporation reduces viscoelastic damping beyond that possible by matrix volume reduction alone. This was observed in various fibre reinforced polymers and is explained in terms of fibre/matrix interactions.