Experimental Investigation of Dynamic Compression and Damage Kinetics of Glass/Epoxy Laminated Composites under High Strain Rate Compression

Abstract

The choice of composite materials as a substitute for metallic materials in high technological applications such as in the marine field is becoming more pronounced especially due to the great weight-savings these materials offer. In many of these practical situations, the structures are subjected to high impact loads like slamming, impact, underwater explosions or blast effects. Material and structural response vary significantly under impact loading conditions compared to static loading. The mechanical characteristics of these materials are well known for static loading; however, with the strain rate they are likely to evolve (Goldsmith et al., 1995; Shi et al., 1993; Tsai & Sun, 2004; Tsai & Sun, 2005; Gillespie et al., 2005; Brara & Klepaczko, 2007). The behaviour of structures subjected to impact has been of interest to many scientists for design purposes as well as for the purpose of developing constitutive models of the materials tested [7-8]. The study of the composite materials behaviour at high strain rates is still relatively new and reliable data on strain rate effects is very scarce. Even though the problem of obtaining reliable data is accentuated by difficulties encountered in design and conducting impact tests on composites [9], the qualitative relationship between the dynamic constitutive response and the dynamic damage evolution for composites at high strain rates is still far from being fully understood. To investigate the rate-dependent constitutive relations of materials at high strain rates, the Split Hopkinson Pressure Bar (SHPB) technique has been extensively accepted [10]. Experience of the use of SHPB for the investigation of metals has led to the adaptation of this technique for the characterization of laminated polymer composites at medium strain rates. Significant efforts have been made to examine the high strain rate behaviour of more brittle materials such as composites and ceramics using the split Hopkinson bar to measure dynamic response of materials under varying loading conditions (Kumar et al., 1986); (El-Habak, 1991), (Harding, 1993), (Sierakowski & Nevill, 1971). Ochola et al. (2004) studied the strain rate sensitivity of both carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP). The results show that the dynamic material strength for GFRP increases with increasing strain rates and the failure strain for both CFRP and GFRP is seen to decrease with increasing strain rates. Vinson & Woldensenbet’s (2001) results show that the ultimate stress