Effect of elastic target on Taylor–Hopkinson impact of low-density foam material

Abstract

As a common approach to evaluate the dynamic strength of cellular materials, the Taylor–Hopkinson test is often carried out by utilizing cylindrical cellular samples striking on the Hopkinson bar axially and determining the dynamic stress through the final deformation of the projectiles. However, extensive related theoretical analyses regard the Hopkinson bar as a rigid wall and ignore the influence of the elastic target bar, which may lead to inaccurate estimation of the dynamic stress of foam materials. In this work, a theoretical model for a low-density foam projectile impinging against a semi-infinite elastic target bar is presented to investigate the effect of elastic target bar on the dynamic stress prediction of the Taylor–Hopkinson test. A shock wave model incorporating the elastic wave propagation in the target bar is developed to obtain the deformation history and kinematic process of the foam projectile. It is demonstrated that the elastic properties of the target bar have a significant effect on the duration and deformation of the impact process. It is also indicated that the material and geometric parameters of the foam projectile and the target bar, and the initial velocity of the foam projectile have great influence on the impact–contact duration and the final deformation of the foam projectile. The history and final deformation of the foam projectile predicted by the present model are compared well with experimental results and finite element simulations. The present analysis provides a more accurate way to take advantage of the Taylor–Hopkinson test to predict the dynamic behavior of low-density foam materials.