Abstract
The residual effects of thermal aging of Kevlar 49 fibers in the temperature range 150-450′C have been analyzed. Thermal aging introduces crystallographic as well as macro-structural changes. Weight losses and deterioration in tensile properties were also observed. The order in which the deterioration in crystallinity, weight and tensile strength occur has been identified. Master curves for predicting the time needed for 50% deterioration at various temperatures and the corresponding activation energy have been estimated. The role of the parameter, t cum(T), the cumulative exposure to any temperature T, on thermally induced effects has been unambiguously established. In particular, the influence of the T- t cum(T) effect on crystallographic parameters has been observed for the first time.
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