On the use of dynamic mechanical thermal analysis (DMTA) for measuring glass transition temperature of polymer matrix fibre reinforced composites

The influence of test parameters such as static and dynamic test loads and fiber orientation in polymer matrix fiber reinforced composites was analyzed and measured. The tests were carried out on unidirectional carbon fiber cyanate-ester matrix composite materials. It was found that the value of glass transition temperature (Tg) determined using dynamic mechanical thermal analysis (DMTA) can be influenced by the applied test loads. For temperatures lower than Tg, the dynamic component was controlled in displacement control mode both in the static and the dynamic component. For temperatures equal or higher than Tg, both the dynamic and static components were controlled in displacement control mode. The results show that testing identical materials with different values of the applied preload produces different values of Tg. The observed dependence of the measured Tg from the preload is relevant to the problem of standardization of DMTA for measuring Tg in composite materials.