High strain rate studies for different laminate configurations of bi-directional glass/epoxy and carbon/epoxy composites using DIC

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The strain rate dependence of glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) composites was experimentally characterized over the range of strain rates (1.6 × 10−3–542 s−1) by performing a series of tensile tests on (0/90), (0/90/30/−60), (0/90/45/−45) and (30/−60/60/−30) laminate specimens. The Digital Image Correlation (DIC) technique was employed by using a high-speed camera to measure the displacement field in-situ on a specimen surface and the results were coupled to Scanning Electron Microscopy (SEM) examinations. The experimental results were validated and strain rate parameters were estimated using the Cowper-Symonds model. These parameters will be useful for designers to validate numerical simulations with experimental values for accurate simulation of the structural performances. The results indicate that the tensile strength and modulus increase and the percent of failure strain decreases for both GFRP and CFRP composites of all lay-up sequences, with the change in strain rate from quasi-static to 542 s−1. The strain rate effect was found to be more for all laminate configurations of GFRP composites than CFRP composites. For the same lay-ups of GFRP and CFRP composites, the recorded tensile strength and modulus are higher and the failure strain is lower for CFRP composites than GFRP composites. In both GFRP and CFRP composites, the (0/90/45/−45) laminates have more strain rate sensitivity compared to the laminates of other orientations.