Loading rate effect on mode I interlaminar fracture of carbon/epoxy composite

Fracture testing was performed for the Carbon/Epoxy double cantilever beam specimens to investigate the effect of loading rate on the interlaminar fracture toughness of composite laminate. Fracture toughness was obtained from the relationship of displacement and crack length. It showed little change up to 2 mm/sec of loading rate, however, 44% increase was observed at 20 mm/sec and 73 % increase at 120 mm/sec. Critical crack propagation speed was found to be between 6 mm/sec and 14 mm/sec from the change of fracture toughness for crack propagation speed which divides static loading range and high rate range.