Influence of composition on mechanical behaviour of porcelain tile. Part II: Mechanical properties and microscopic residual stress

The influence of the starting composition on the mechanical properties of sintered porcelain tile was evaluated based on the linear elastic fracture mechanics. Tile compositions were prepared according to a simplex-centroid mixture design set out in part I of this research. Results were analyzed based on the linear elastic fracture mechanics. The Irwin equation and the experimental data were treated according to a Taylor's series expansion. This methodology made it possible to evaluate the mechanisms which are more relevant for strengthening and the role of each component of the system.It was observed that the phase composition affects markedly the mechanical strength of porcelain tile mainly by changes in fracture energy. Young's modulus and flaw size have also a notable but less important influence. Wide variations in flaw size can cause a more severe impact on the mechanical strength. In turn, the fracture energy is equally affected by the state of microscopic residual stress and the deflection in crack propagation. Regarding to the contributions of the each phase component, it was noticed that mullite and kaolinite glass significantly worsen the fracture energy while quartz particles have a decisive contribution on increasing the fracture energy. Finally, the results confirm once again that the Selsing equation can be used for estimating microscopic residual stress on quartz particles in porcelain tile.