TRANSFORMATION TOUGHENING OF A CALCIUM ZIRCONATE MATRIX BY DICALCIUM SILICATE, UNDER BALLISTIC IMPACT

摘要

Preliminary investigations have been made on toughening ceramic armor materials by inducing large volume change phase transformations in ceramics. Such transformations cannot be induced by a normal, slow crack growth mechanism such as occurs in zirconia, but requires an exceedingly high activation energy barrier to be overcome. We have developed a procedure for evaluating mechanical behavior under both quasi-static and dynamic loading conditions. The failure modes under quasi-static loading conditions were observed to be non-catastrophic. Preliminary results suggest that dicalcium silicate (CaiSiO{sub}4 dispersed in a calcium zirconate (CaZrO{sub}3) matrix material increases the toughness of the material. It is thought that the energy of ballistic impact is able to overcome the prohibitively, high activation energy barrier to nucleate the orthorhombic to monoclinic transformation in Ca{sub}2SiO{sub}4 which is accompanied by an ～12% volume increase at 490℃.