Computational modeling of composite armour and effect of CNT inclusion using orthotropic material model

Abstract

We report development of indigenous Material Point Method (MPM3D) and Smoothed Particle Hydrodynamics (SPH3D) codes for modeling and design of composite body armour. Typical armour consists of a ceramic backed by a polymer matrix composite. The ceramic plate contributes to blunting of bullet nose, its erosion and reduction in speed. The polymer matrix with high tensile strength arrests the bullet. Mie-Gruneisen EOS, Johnson-Cook strength and failure models were used for projectile. Johnson-Holmquist (JH2) model was used for ceramics. An orthotropic model which accounts for different compression and tensile properties in through-thickness and in-plane directions was implemented and used for Ultrahigh Molecular Weight Polyethylene (henceforth termed as ‘PE’). The codes were validated against published results for impact onto PE targets. Then the codes were used to simulate various published experiments (of coauthors) on ceramic/PE composite targets performed according to NIJ standards. Back Face deformation (BFS) is measured. In all cases, the projectiles do not penetrate through the armour panels, consistent with experiments. Typically, the SPH and MPM codes compute BFS values which only deviate within 10–20 % of measured values. The simulation results are also compared with the commercial FEM code simulations. Experiments and simulations were carried out for PE reinforced with Carbon Nanotube (CNT) inclusions. The mechanical moduli and other strength parameters of PE are adjusted to account for the increase in flexural strength due to inclusion of CNT. The CNT inclusion greatly reduces the BFS. The simulations results qualitatively follow these trends.