Prestressed composite specimen for mixed-mode I/II cracking in laminated materials

Abstract

This article presents the mixed-mode I/II prestressed end-loaded split specimen for the fracture testing of composite materials. The system is based on the fact that one of the two fracture modes is provided by the prestressed state of the specimen, and the other one is increased up to fracture initiation using a testing machine. The novel beam-like specimen is able to provide any combination of the mode-I and mode-II energy release rates. A simple closed-form solution is developed using beam theory as a data reduction scheme and for the calculation of the energy release rates in the new configuration. The applicability and the limitations of the novel fracture mechanical test are demonstrated using unidirectional glass—polyester composite specimens. If only crack propagation onset is involved, then the prestressed mixed-mode beam specimen can be used to obtain the fracture criterion of transparent composite materials in the G I—GII plane.