An experimental investigation in interlaminar fracture behavior and toughness of multi-directional composite laminates was conducted. ENF-like specimens were used for three-point-bending tests first to determine the crack-jumping behavior in various laminates. It was found that a delamination crack could propagate only along the 0/0 interface. Based on the result of this investigation, an experimental method to determine Mode II dominated interlaminar toughness was proposed and used to obtain interlaminar toughness of 0/0 interfaces in AS4/3501-6 composite material with 0 = 30°, 45°, 60°, and 90°. It was found that the critical strain energy release rate decreases as the off-axis angle 0 increases.
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