Shock compressibility and spall strength of kevlar/epoxy composite

Experimental studies have been carried out on the shock-wave properties of a composite made of aramid ballistic fabric and epoxy binder, with the fibers oriented longitudinally and transversely to the direction of wave propagation. Laser interferometry was used to record particle velocity profiles. The Hugoniot of the composite is shown to be independent of fiber orientation, and a break is observed at 17 GPa, indicating a phase transition. The most striking feature of the velocity profiles in samples with longitudinal fiber orientation is the presence of a two-wave structure at compression pressures below 12 GPa. It is shown that the spall strength of a Kevlar-based composite with a longitudinal fiber orientation is approximately twice that of a transverse fiber orientation and is equal to 180 MPa.