Effects of elevated loading rates on mode I fracture of composite laminates using a modified wedge-insert fracture method

In this paper, experimental results for rate dependence of interlaminar mode I fracture of a polymer matrix composite laminate are presented. A modified wedge-insert fracture (MWIF) method for conducting mode I fracture testing at elevated loading rates is used. A correction factor has been introduced to the modified beam theory method for measuring the mode I interlaminar fracture toughness using the MWIF method. The experimental method was successfully verified against the most widely used standardized method at quasi-static loading rates. Mode I interlaminar fracture testing was conducted at loading rates ranging from 0.01 mm/s to 3600 mm/s. A reduction in fracture toughness with rate was seen. The fracture behavior at elevated rates differed from the lower rates. The effect of bridging (and process zone) lengths on the fracture toughness were seen decreasing drastically with increased loading rate.