DELAYED FAILURE IN SHOCKED SILICON-CARBIDE

Plate impact and split Hopkinson pressure bar (SHPB) experiments have been conducted on three grades of silicon carbide produced by differen t routes. Data are presented which indicate that the failure of the ma terials was delayed for some time after the maximum stress had been ac hieved, In particular, the measured lateral component of the stress in plate impact was found to increase across a front which traveled behi nd the shock. This phenomenon is akin to the failure wave which has be en observed to occur in glasses but has not previously been reported i n polycrystalline materials. Hopkinson bar experiments have revealed s ignificant differences in the behaviors between the three materials. T hese may be related to the effects observed in the plate impact experi ments. These results explain the anomalous ballistic phenomena that ha ve been reported for the penetration behavior of SiC. Additionally the Hugoniot elastic limit (HEL) and shear strength were found to vary wi th the production route used. (C) 1997 American Institute of Physics.