BALLISTIC DAMAGE OF ALUMINA CERAMICS - LEARNING FROM FRAGMENTS

We have used transmission electron microscopy (TEM), optical luminescence microscopy (OLM) and scanning electron microscopy (SEM) to study the characteristics of the surfaces of alumina ceramic fragments generated by ballistic impact. The identified characteristics - transgranular fracture, intergranular fracture, plastic deformation and microcracking - showed a strong association with the sizes of fragments. Collected fragments with different sizes were quantitatively mapped against these characteristics, and a transition can be distinguished from such mapping. A cavity-expansion model is adapted to describe the ballistic impact, and fragmentation is estimated using Grady's model with surface characteristics accounted. This study demonstrates that characteristics on fragments at different length scales are informative for understanding the ballistic damage of alumina ceramics.