Perforation of concrete targets

During construction of concrete buildings for military purposes, one is interested in minimizing the potensial damage caused by an impacting projectile. To achieve this, it is necessary to use a wall thickness that either stops the projectile from perforating the structure, or at least reduces the residual velocity considerably. In this report, a new analytical approach for calculating the penetration process of a rigid projectile in a finite structure is presented. The method is based on cavity expansion theory and uses a force reduction factor to decrease the force on the projectile when it is close to the rear side of target, giving a more realistic expression for the force. Both ballistic limit, residual velocity and required wall thickness to prevent perforation can be determined from the model. On comparison with experimental data, the new model gives good agreement and is seen as a vast improvement over existing empirical models. Using the new method together with the models for semi-infinite targets, we have a complete collection of powerful analytical tools for analysing normal impact of rigid projectiles against concrete targets.