Abstract
PBX solid high explosive exhibits brittle behaviour in uniaxial tension, quasi-brittle in uniaxial compression, and ductile when subject to high confining pressure. Tension cracking is the primary failure mode of PBX quasi-brittle solid, which is the main effect leading to overall failure of structural integrity. One characteristics of brittle or quasi-brittle solids, such as PBXs, is that when subject to overall compressive loading, the tensile cracks can still initiate inside the material due to existence of imperfection within the materials. In present study the extended finite element method is applied to analyze the cracking failure mechanism in the PBX 9502 platelike specimen with cavity subjected to overall compression. The nonlinear constitutive behaviours and failure of PBX under complex stress states were described by means of stress state dependent strength surface, non-associated flow rule and cohesive model the nonlinear behaviors of PBXs, including failure. Analysis indicates the tensile stress around the cavity arises in the specimen although loaded by overall compression, and this local tensile condition leads to cracking initiation. The comparison between simulation results and the experimental data published by LANL[Liu C, Thompson D G. Crack initiation and growth in PBX 9502 high explosive subject to compression. Journal of Applied Mechanics, 2014, 81(10):212-213] shows that they are in agreement with each other on some aspects of crack behaviours, including overall development of crack history and inflexion, crack initiation moment, crack initial speed, etc.
Highlights
Polymer-bonded explosives (PBXs), highly particle filled composite materials comprised of 90–95% by weight of powerful explosive crystals held together by a polymeric binder (5–10% by weight), have been used in a wide variety of applications ranging from rocket propellants to the main explosive charge in conventional munitions for civil and defence fields[1,2,3,4]
It is found from the experimental observation that the plastic deformation and subsequent cracking problems of the energetic materials directly affect the evolution of the reaction and the reaction level [14]
XFEM is a new finite element method to solve the problem of fracture mechanics
Summary
Polymer-bonded explosives (PBXs), highly particle filled composite materials comprised of 90–95% by weight of powerful explosive crystals held together by a polymeric binder (5–10% by weight), have been used in a wide variety of applications ranging from rocket propellants to the main explosive charge in conventional munitions for civil and defence fields[1,2,3,4]. It is generally believed that the ignition mechanism of explosives under low velocity impact includes: elastic-plastic or visco-elastoplastic deformation, damage and failure, crack initiation and growth, plastic localization and plastic work conversion into heat and heat conduction [13]. It is found from the experimental observation that the plastic deformation and subsequent cracking problems of the energetic materials directly affect the evolution of the reaction (such as increasing the surface area will accelerate the combustion rate) and the reaction level [14]. Analyse the crack initiation and failure of PBX 9502 plate with cavity against compression failure test [26]
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