Evaluation of the accuracy of the four-point bend end-notched flexure test for mode II delamination toughness determination

Results are presented from an experimental study to investigate the accuracy of the four-point bend end-notched flexure (4ENF) test for the determination of mode II delamination toughness. In previous studies, 4ENF tests have yielded higher delamination toughnesses than the more commonly used three-point bend end-notched flexure (ENF) test. In a recent finite-element study, it was found that the higher toughnesses found by the 4ENF test cannot fully be attributed to frictional effects. This current study was performed in order to examine if the difference between ENF and 4ENF results is due to current methods used to determine crack length and compliance during a 4ENF test. It was found that if these two parameters are measured accurately then the 4ENF test yields toughnesses similar to those obtained from ENF testing.