NUMERICAL SIMULATION OF IMPACT ON CERAMIC ARMOUR SYSTEM.docVIP

NUMERICAL SIMULATION OF IMPACT ON CERAMIC ARMOUR SYSTEM The work reports on numerical simulation of impact problems on ceramic/aramid armour systems backed with Kevlar 29. Tests were performed with STANAG 2920 fragments and NATO 5.56 bullets driven at velocities up to 1100m/s. In order to obtain the best ballistic efficiency of the composite armour system three configurations of the armour system was taken into account in numerical simulations, varying the thickness of ceramic front plate. The thickness of backed plate was maintained constant at 2 mm. The configurations are contemplated in the table 1. Table 1 Configuration Ceramic/Kevlar thickness ratio (h1/h2) C1 5 C2 7.5 C3 9.5 The ballistic performance of the lightweight armour systems was examined to obtain an estimate for the global damage of the composite plates. Material models The Mohr-Coulomb (MC) strength model and linear equation of state (EOS) are used to model the ceramic layer. The micro mechanical failure of ceramic is modelled using a cumulative damage model. Since experiments indicate that ceramics show a marked increase in compressive strength as the hydrostatic pressure is increased, it is most likely that this model will be used in conjunction with the Mohr-Coulomb model which uses a yield strength that is a function of the local hydrostatic pressure. An advanced orthotropic model [1] implemented in Autodyn hydrocode, which use non-linear equation of state in conjunction with an orthotropic stiffness matrix is used to model the Kevlar 29/Epoxy layer. The 4340 steel used for STANAG fragments was represented using the Johnson Cook strength model, which include strain and strain rate hardening and thermal softening effects. A model of the NATO 5.56 bullet was developed using material data available from existing Autodyn model libraries and parameters modified based upon the measured hardness of the bullet′s individual components. The bullet is of three-part construction wit