Shear and spall strength of polycarbonate under plane shock loading

Plate impact experiments have been conducted to investigate the shear and spall strength of polycarbonate under plane shock loading. Stresses in the longitudinal and transverse directions relative to the direction of shock wave propagation have been measured with manganin stress gauges, and shear strength has been determined from the stress difference. Spall strength has been determined by measuring the free surface velocity profile of the back surface. Shear strength increases with increasing shock strength in the stress range up to 3 GPa. However, for shock stresses above 3 GPa, the shear strength decreases with increasing shock stress, and under the stress of 5 GPa, the shear stress can hardly be maintained. The spall strength is almost constant for shock stresses up to 2 GPa and decreases for higher stresses. However, in contrast to the case of shear strength, sufficient spall strength is maintained even at a shock load of 5 GPa. The boundary of the shock stress at which the spall strength decreases corresponds to the boundary at which the U_s-u_p linear relationship changes.