Importance of hardness and toughness in ceramic armour

Extensive studies on ceramic armour had been conducted since the late 1960s, laying down the foundations for ceramic armour studies today. However, most of the work done has focussed on small calibre projectiles; i.e. 7.62 mm projectile, with limited work on long rod projectiles. Of these, there is a lack of studies that investigate relationships between hardness and fracture toughness of ceramic armour module components. On top of that, there is no consensus in the community on the relationship between ceramic hardness and its ballistic performance. The overall objective of this study was therefore to understand the influence of hardness and fracture toughness of ceramic armour module components on the ballistic performance of ceramic armour against long rod projectiles. The strategy to understand the correlation between hardness and toughness of various component of ceramic armour and its ballistic performance was through experimentation using surrogate long rod projectile against modified ceramic armour modules. Computer simulations using LS-Dyna were then applied to understand the mechanism and the role each material properties played within a ceramic armour system. This study emphasised on the three primary components of a ceramic armour module: (1) cover plate, (2) ceramic and (3) backing plate. Cover plate hardness did not affect the ballistic performance of ceramic armour module. The ballistic performance was reduced by decreasing cover plate fracture toughness due to the early loss of confinement pressure which resulted in premature dwell termination. By increasing ceramic hardness from 20.6 GPa to 24.4 GPa, mass efficiency of the armour module increased from 1.52 to 1.73. In contrast, fracture toughness did not influence the performance of the module. However, fracture toughness of ceramic highly influenced the damage radius, i.e. damage condition of neighbouring tile. When fracture toughness increased from 2.84 MPa.m1/2 to 6.99 MPa.m1/2 the damage radius reduced from 420 mm to 138 mm. Backing plate hardness was observed to have the most significant influence on the ballistic performance of a ceramic armour module. When backing plate hardness increased from HRC 30 to HRC 50, the ballistic performance increased from 1.29 to 1.84, an increase of 43% in ballistic performance; as compared to 0 % improvement for cover plate hardness over the same range. Through the work conducted, the following conclusions were drawn; hardness and toughness of the components in ceramic armour worked toward influencing the dwell time. The cover plate was observed to be of critical importance in establishing dwell while ceramic and backing plate contributed to sustaining the dwell. Lastly based on the research findings, an optimized armour was designed. The cover plate was first optimized based on maximizing the dwell time to areal density ratio. It was followed by the optimization of the ceramic to backing ratio. The best configuration was determined based on dwell time and DOP measurement.Doctor of Philosoph