Indentation - a method for classification of armour ceramics?

Ceramics have been used in armour applications for a long time due to their hardness and relatively low weight. The increasing demand of ballistic protection has given a rapid development of a large number of new types of ceramics with potential as armour. This trend in connection with the high cost of ballistic testing has shown a need for a fast and non expensive mechanical test that can be related to the ballistic performance of the developed ceramics. In this report the possibility of using different indentation methods as a tool for ranking of armour ceramics are discussed. In addition, an investigation where the hardness, fracture thoughness and ballistic performance of some ceramics are presented. Two test series are done. In the first three different ceramics (silicon carbide, titanium diboride and boron carbide) are compared and in the second series four different qualities of silicon carbide. The literature study in connection with the results found in this investigation show that indentation methods can be used, at least as a part in a programme to rank armour ceramics. The result also show that for ceramics of the same type (silicon carbide) but different qualities an increase in fracture thoughness may be related to an increase in ballistic performance. On the other hand the hardness did not correlate to protectional capability. For ceramics of different types no correlation between hardness, fracture thoughness and ballistic performance could be seen.