Abstract
In this study, the Arcan type test method is adopted to evaluate the fracture toughness of the unidirectional FRP(GFRP, CFRP）under mixed mode loading. The effects of the mixed mode ratios on the fracture toughness and the difference of the fracture toughness between reinforced fibers are investigated. By incorporating the effect of proceeding micro crack which is observed during the experiment, it could simulate the entire fracture process including the initial failure process, and the propagation of the damage zone was also well represented by applying the analytically obtained fracture elements. Considering an orthotropic property of the unidirectional FRP, the stress intensity factor at the starting point of crack initiation was calculated by finite element method. Consequently, in the case of GFRP, a mixed mode fracture criterion is proposed in the form of an ellipsoidal curve. On the other hand, in the case of CFRP, it is proposed in the form of an ellipsoidal curve and a line on K Ⅰ and K Ⅱ plane. The physical meaning of the fracture toughness obtained in this study was discussed. A good agreement with whole fracture process between the experimental and the analytically obtained results was observed.
Finally, for the unidirectional FRP specimen subjected to mixed mode loading, the validity of the elasticplastic analysis using Hoffman's law as a condition of fracture was discussed and the validity of this modeling of the proceeding micro crack was also examined.
