SHOCK COMPRESSIBILITY AND SPALL STRENGTH OF TWO COMPOSITE MATERIALS BASED ON ARAMID FIBERS*

Using a VISAR laser interferometer, the experiments on investigation of the shock wave structure, spall strength and determination of Hugoniot were performed for two composites based on aramid fibers - textolite and kevlar. They have the same compound, but different structure. The density is 1.27 g/cc. To study the shock wave compressibility of composites under extreme conditions, the explosive propellant charges were used. On the velocity profiles with transverse fiber orientation, for both materials after the initial shock jump, oscillations are observed due to the heterogeneous structure. When a shock wave propagates along the fibers, a two-wave configuration is recorded, which is due to the anisotropic structure. For each composite, Hugoniot data were obtained for two orientations. It was found that Hugoniots for transverse orientation of the fibers are parallel to each other and differ only in the first coefficient determined by the sound speed of the material. For both materials, the value of spall strength along the fibers is several times higher than that for the transverse direction. It was found that shock wave properties of textolite and kevlar were strongly dependent on the orientation and structure of the fibers.