Dynamic failure and fracture mechanism in alumina ceramics: Experimental observations and finite element modelling

The application of ceramics in composite armour requires the investigation on the failure and fracture mechanisms of the ceramics under dynamic loading. In this study, the split-Hopkinson pressure bar technique with high speed photography was used to directly observe the dynamic macro-cracking and fragmentation process in alumina and to characterise the stress and strain histories. An experimentally validated 3D finite element model of the full scale test was developed to predict the stress distribution and damage evolution in alumina that were related to the experimental observations. It was found that the damage (cracking) evolution is determined by the multiaxial stress state, in particular the substantial localised tensile stress concentration and the stress direction. The cracking process leads to the longitudinal axial splitting failure on the surface and the internal diagonal damage bands. The dynamic failure process in alumina is dominated by both the intergranular and transgranular fracture mechanisms