Time-temperature dependent mechanical properties of cured epoxy resin and unidirectional CFRP

For composite structure design, determining the relationships between failure time and mechanical properties in the full range of working temperatures is essential. Dynamic mechanical analysis (DMA) and tensile tests were performed to get the dynamic and static mechanical properties of resin 5228A respectively at various temperatures. The master curves of storage modulus and Young's modulus were constructed at selected reference temperature 25°C using closed form shifting (CFS) method based on the time-temperature superposition principle (TTSP). During the shifting procedure of storage modulus, corresponding time-temperature shift factors were obtained, which meet the Arrhenius equation very well. Finally, the master curves of transverse and longitudinal compressive strength were constructed at 25°C by shifting the compression tests data of unidirectional laminates CCF300/5228A horizontally with the time-temperature shift factors obtained previously. Results show that both dynamic and static mechanical properties of the resin 5228A are obviously time-temperature dependent, higher frequencies induce more elastic-like behavior, transverse and longitudinal compressive strength decreases significantly with increasing failure time.