抄録
End-notched flexure (ENF) test is commonly accepted to determine the mode II interlaminar fracture toughness of composite laminates. As the crack propagation in the ENF specimen is unstable under displacement-control, the critical energy release rate, GIIC, is determined at the onset of crack initiation but not during the crack propagation. In order to estimate the mode II fracture toughness from the initiation to the stable crack propagation, a new test method has been proposed in the present paper. A special COD gauge has been developed for the measurement of the crack opening displacement (COD) of ENF specimen and applied to the mode II interlaminar fracture toughness test. The crack initiation in the ENF specimen can be detected with higher accuracy from the load-COD diagram than the load-displacement dia-gram. Moreover, the crack propagates in the stable manner under the COD-control test, though it is unstable when the conventional displacement-control test is applied. Analytical compliance method has been successfully applied to the ENF test and the relation between fracture tough-ness, GIIC, and crack length, a, can be obtained automatically by using a computer aided test-ing system. Applicabilities of the COD-control test and the analytical compliance method to the ENF test are confirmed in the present paper.
