Effects of temperature and moisture on the high strain rate compression response of graphite/epoxy composites

Experimental investigations were carried out on unidirectional Graphite/Epoxy laminate samples under dynamic compression loading using a modified Split Hopkinson Pressure Bar. High strain rate testing was carried out at room and elevated temperatures. 30 layered graphite/epoxy unidirectional laminates made using DA 4518U unidirectional prepregs system were fabricated. Tests were carried out on samples at room, 51.7degreesC, 121.1degreesC, and 190.6degreesC temperatures. Additional high strain rate tests were conducted on samples that were subjected to moist/freeze conditioning for 42 days. Failure modes were studied through scanning electron microscopy. Results of the study indicated plasticizing of matrix which was reflected through increased ductility of the samples as well as reduced slope of the stress-strain curves with the increase in temperature. Similar effect was evident in the samples that were subjected to moist/freeze conditioning.