Influence of the Third Invariant in the Ballistic Impact of Silicon Carbide

This report examines the dependence of the ballistic performance of silicon carbide on the third invariant of the stress tensor by use of numerical simulations and test data. The JHB ceramic model is modified to account for the influence of the third invariant, and the modification includes a material parameter defined as the ratio of yield in tri-axial extension to yield in tri-axial compression. Simulations of high-velocity impact are performed systematically with several values of the parameter to determine the influence of the third invariant. The simulation results are also compared to test data to determine the degree of influence that provide s the best agreement. Simulations include tensile and compressive plate-impact tests, long-rod penetration of prestressed targets, long-rod penetration of confined targets, long-rod penetration of unconfined targets, and ballistic impact of thin targets with substrates.