Dynamic mechanical analysis of pultruded glass-graphite/epoxy hybrid composites at elevated temperatures

In this paper the dynamic performance characteristics of pultruded glass-graphite/epoxy hybrid samples at elevated temperatures are presented. In previous research the dynamic mechanical properties of the hybrid composites have been characterized at room temperature but the wide application range of these pultruded products necessitates their characterization at high temperatures and over longer periods. The dynamic mechanical analysis technique has been employed to characterize pultruded glass-graphite/epoxy hybrid composite materials over a wide temperature range. At elevated temperatures, the rate of degradation in flexural modulus and variation in loss factor were found to be dependent on the fiber lay-up sequence. Results indicate that the width of the glass transition zone, an important design criterion, can be effectively broadened by judicious incorporation of the glass fibers. Tests repeated on post-cured pultruded products demonstrate a significant shift in the glass transition temperature towards higher side along with an increase in the onset temperature of glass transition. The frequency multiplexing technique used in conjunction with the time-temperature superposition principle proved to be an effective method for predicting the long-term behavior of these hybrids.