A novel test system for mixed mode-I/II/III fracture tests - Part 2: Experiments and criterion development

In this part of the study, details of mixed mode-I/II/III fracture experiments for the CTST (Compact Tension-Shearing and Tearing) specimen, for which modeling and analyses results are given in Part 1, are presented. Critical fracture loads obtained from the tests are used with knowledge of mixed mode stress intensity factors (SIFs) from three-dimensional fracture analyses (Part 1) to compare with criteria existing in the literature for mixed mode-I/II/III fracture conditions. It is observed that existing criteria start deviating from the experimental measurements for cases in which coupled modes-II and -III are dominant under general mixed mode loading conditions. Similar studies are also performed for the same specimen under different out-of-plane mixed mode-I/III loading cases. Similarly, higher discrepancies are obtained for prediction of unstable fracture load values between fracture criteria and experimental results for highly mode-III conditions. Therefore, an improved empirical mixed mode-I/II/III fracture criterion is developed using all data obtained from numerical and experimental analyses. The results show that the improved criterion gives considerably good congruence with the experimental measurements