Temporal pattern of microcracking in impact-damaged porous SiC ceramics

Abstract

Temporal characteristics of the localized damage development initiated by a short-time impact pointed loading of SiC ceramics which is widely applied as a protective material against the shock action upon engineering constructions and people were investigated. The statistics of crack nucleation and relaxation was studied with the methods of acoustic emission and electromagnetic emission, correspondingly. It was shown that the length of intervals between microcrack nucleations follows a power law specific to cooperative phenomena. The time distribution of decaying electric charges which appear on impact-induced crack edges and annihilate after the passage of impact wave was, in contrast, linear. The temporal pattern of the crack relaxation permitted identifying two sets of newly formed damages that are the tiny cracks localized in the grain bulk and those that interconnect grains. Keywords: SiC, porous ceramics, impact damage, acoustic emission, electromagnetic emission.