AN EMPIRICAL STRAIN RATE-DEPENDENT CONSTITUTIVE RELATIONSHIP FOR GLASS-FIBER-REINFORCED EPOXY AND PURE EPOXY

An investigation into the effect of strain rate on glass-fibre reinfor ced plastic (GFRP) and pure epoxy subjected to compressive loading has been conducted. Experimental results in this study were obtained by a hydraulically driven Instron Testing machine and a Split-Hopkinson Pr essure Bar. The range of strain sates explored was between 5x10(-4)/s and 2500/s. A comparison between the behaviour of pure epoxy and GFRP reveals that both are strain rate sensitive, especially in the low str ain rate regime. There is also a significant increase in the dynamic m odulus as strain rate increases. It is shown that the stress-strain re sponse under dynamic loading is not only a function of strain rate, bu t also of the strain state. An empirical equation incorporating both s train and strain rate terms is proposed and is found to adequately des cribe the stress-strain behaviour of both GFRP and pure epoxy for the range of loading rates studied.