Finite strain analysis of deformations of quasibrittle material during missile impact and penetration

The conference presentation deals with three problems involved in finite element analysis of the impact of missiles into reinforced concrete walls and their penetration through the walls: (1) Formulation of the constitutive law for complex nonlinear triaxial behavior of concrete, including the strain-softening damage; (2) extension of the formulation to very large finite strains; and (3) application of the model in dynamic finite element analysis. Only problem (2) is discussed in some detail in this brief paper. Because the Biot strain tensor has a clear physical meaning even for very large finite strains, its use is preferable in the fitting of complex triaxial test data. It is shown that the constitutive relation can be conveniently formulated as a relation of the Biot strain tensor to the back-rotated Cauchy stress tensor, and the justification of this form of the constitutive relation is given.