Numerical modeling of crack growth in polymer-bonded explosive with cavity subject to compression

Polymer-bonded explosives are solid high-explosive particles that exhibit brittle behavior in uniaxial tension, quasi-brittle in uniaxial compression, and ductile when subjected to high confining pressure. Tension cracking is the primary failure mode of polymer-bonded explosives quasi-brittle solid, which will lead to overall failure of structural integrity. One characteristic of brittle or quasi-brittle solids, such as polymer-bonded explosives, is that when subjected to overall compressive loading, the tensile cracks will initiate inside the material due to existence of imperfection within the materials. In this study, extended finite element method is applied to analyze the cracking failure mechanism in the PBX 9502 plate-like specimen with cavity subjected to overall compression. The nonlinear constitutive behaviors and failure of polymer-bonded explosives under complex stress states were described by means of stress state–dependent strength surface, non-associated flow rule, and cohesive failure model. Analysis indicates that the tensile stress around the cavity arises in the specimen under overall compression, and this local tensile stress will lead to cracking initiation. The comparison between simulation results and the experimental data reported by Liu and Thompson shows that they are in agreement with each other on some aspects of crack behaviors, including overall development of crack history and inflection, crack initiation moment, and crack initial speed.