The relative residual fibre displacement after indentation loading and unloading of fibre-reinforced ceramic composites

The interfacial properties of fibre-reinforced ceramic composites have been evaluated by using the indentation technique. The ratio of the residual fibre displacement after complete unloading to the fibre displacement at peak loading is examined. Assuming a constant interfacial shear stress at an unbonded interface, this ratio is 0.5. However, deviation of this ratio from 0.5 is always obtained from experimental results. Both Poisson's effect and the existence of the residual axial stress have been proposed to explain this deviation. A methodology is presented in this study to classify conditions for which either Poisson's effect or the residual axial stress dominates this deviation. The application of this methodology to Nicalon fibre-reinforced lithium aluminosilicate glass-ceramic is also illustrated.