Indentation size effect of alumina ceramic shocked at 12Â GPa

► Strong ISE in Nanohardness of Shocked Alumina. ► Weak ISE in Nanohardness of As Received Alumina. ► Explanation of ISE by concept of Interaction between Nanoindent and Microstructural Damage. ► Extent of ISE controlled by relative ease of Indenter penetration governed by relative frequency of Multiple Micro pop in Events. ► Important role of Shear stress generated just underneath the nanoindenter.