Indentation and acoustic emission in filtration processed platelet reinforced ceramics

Al2O3-platelet reinforced zirconia ZrO2 composites were fabricated by the filtration method. The elastic constants of composites predicted by the effective medium theory compare very well with experimental values. The fracture toughness of materials was measured by the indentation technique. Incorporation of 5 wt.% platelets in the matrix material increased the fracture toughness by 16% as compared with the pure matrix. During the indentation experiments the acoustic emission activity was monitored, indicating that the indentation crack is formed under increasing loading and it ceases to develop shortly after the indentation force reaches a nominal value. Variations in the acoustic emission energy and the amplitude distribution were related to the crack length and a presence of platelets in the matrix.