Development of a constitutive model for numerical simulation of projectile penetration into brittle geomaterials

James Donald Cargile, Purdue University

Abstract

A nonlinear, inelastic fracture model for brittle geomaterials has been developed for simulating the response of these materials to high-velocity projectile penetration. Laboratory mechanical property experiments show a transition in the shearing response for these materials from brittle at low pressures to ductile at high pressures. The model has the underlying assumption that the shearing response can be resolved into a brittle cohesive component and a ductile frictional component. At low pressures the cohesive component controls the behavior and the material response is brittle. As pressure increases, the cementing bonds that hold the aggregate particles together are broken and the contribution of the cohesive component decreases while the contribution of the frictional component increases. Once the bonds are completely broken, the material response is determined only by the ductile frictional component. The model response agreed well with the results from various quasi-static triaxial experiments on concrete samples. The model is implemented into a finite-element code and used to simulate high-velocity projectile penetration events. A series of laboratory penetration and perforation experiments were conducted and used to evaluate the model within the finite-element wave propagation code. Penetration experiments were conducted by launching robust steel projectiles into semi-infinite concrete targets to obtain depth of penetration and crater profiles at impact velocities ranging from 277 to 800 m/s. Perforation experiments were conducted by launching robust steel projectiles at 313 m/s into concrete slabs measuring 127 to 284 mm thick to obtain exit velocity and crater profiles. High-speed movies of the impact and exit faces of the targets showed the evolution of surface damage during the perforation event. Depth of penetration and exit velocity from simulations of the penetration and perforation experiments agree well with the experiment results. The simulations show the break-up and damage to the target during formation of the impact crater and tunnel in the deep penetration experiments and the impact and exit craters in the perforation experiments.

Degree

Ph.D.

Advisors

Bourdeau, Purdue University.

Subject Area

Civil engineering|Mechanics

COinS