Creep behavior of polyetherimide semipreg and epoxy prepreg composites: Structure vs. property relationship

In the present study, the creep behavior of polyetherimide semipreg and epoxy prepreg composites was studied using dynamic mechanical analyzer and focused on structure vs. property relationships in glassy, glass transition, and elastomeric regions. The main contribution to the field is to study pre-impregnated materials concerning creep behavior, mainly based on different analytical models, and microstructure. Two different reinforcements were used (carbon fiber and glass fiber) for each matrix. Findley, Burger, and Weibull analytical models were applied with an excellent fit for the most of them. The impregnation quality, verified by C-scan and the void content by acid digestion, shows different impregnation behaviors, mainly for epoxy/CF, which also influenced molecular motion behavior. The creep behavior was mainly influenced by matrix type than reinforcement architecture and void content. In addition, the creep was higher for epoxy in the glassy region; however, in the glass transition region, higher deformation was found for polyetherimide composites. Previous behavior is mainly attributed to higher energy storage in the glassy region which plays a significant role in the dissipation (glass transition energy), resulting in the energy loss or the drop of storage modulus in a narrow temperature range - more abrupt. This behavior was corroborated by time-temperature superposition curves in which the low deformation obtained for polyetherimide composites at low temperatures is maintained only until the glass transition temperature. Epoxy composites showed a higher initial creep deformation, but the values were almost constant with temperature, even when the temperature passes by the glass transition temperature.