New insights into nanoindentation crack initiation in ion-exchanged sodium aluminosilicate glass

The effect of ion-exchange on the fracture behavior and the threshold load is investigated for radial crack initiation resulting from cube-corner indentation. Both tin and air sides of the sodium aluminosilicate float glass are considered. The threshold load and mechanical properties are experimentally measured by nanoindentation. A qualitative explanation of crack initiation is developed by analyzing the stresses at the indentation site. The ion-exchanged glasses show a lower threshold load for radial crack initiation with a cube-corner indenter than the raw glass, and this is due to a higher crack driving stress for ion-exchanged glasses. However, the compressive stress on the surface of the ion-exchanged glasses can inhibit the expanding of the radial cracks. The air side always shows higher values for the threshold load than the tin side before and after ion-exchange, which is in accordance with the calculated crack driving stress results