A complex study was performed over several years with laboratory-made ceramic tilesto enable ballistic tests with a separate variation of selected influences keeping otherfactors constant. These investigations were aimed at answering the question about influencesof different microstructures and of associated mechanical properties dependingon systematic variations of the backing materials. Contradictive findings of the pastare explained now by the observation that the ballistic strength of Al2O3 and spinel ceramicsand single crystals with different backings (steel, aluminum, glass) is governedby a few major influences subject to a strict hierarchy: (1) Top priority is the mode ofceramic fragmentation governed by the microstructure and by the dynamic stiffness ofthe ceramic/backing target; these influences also affect the relative importance ofdwell and penetration. (2a) On a lower rank, Young's modulus and dynamic stiffness ofthe ceramic are responsible for projectile deformation during dwell. (2b) On penetration,the abrasive benefit of a high ceramic hardness depends on the size of the ceramicdebris, i.e. on ceramic fragmentation.In contrast, all strength data are weakly correlated with the ballistic efficiency. This resultis readily understood regarding the need of ceramic failure for maximum projectileerosion.
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