On the failure of boron carbide under shock

The failure of brittle materials during uniaxial, compressive shock-loading has been the subject of extensive recent research. For instance, the physical interpretation of the yield point, the Hugoniot elastic limit (HEL), remains poorly understood. Stress and particle velocity records show B(4)C exhibits a type of behaviour different to that of other brittle materials. A number of features have been measured to investigate these features. In other ceramics, failure has been seen to occur behind a travelling boundary that follows a shock front that has been called a failure wave, across which the strength of the material is dramatically reduced. In order to elucidate whether this failure process occurs, gauges were embedded to measure the lateral stress behind the shock front in B(4)C. As in other materials the stress in B(4)C was seen to rise across a failure front. However, this phenomenon only occurred over certain stress ranges. More significantly, the failure penetrated further into the ceramic than has been seen in other materials. A mechanical interpretation is suggested to explain the observed behaviour of B(4)C.