This paper focuses on the study of the flaw tolerance and resistance curve behaviour (R-curve) in 3Y-TZP/Nb composites containing indentation-induced small surface cracks. It has been found that toughening and resistance curve behaviour occurs as a result of the combined effects of crack bridging and transformation toughening. The ZrO_2-Nb composites are described as synergistically toughened composites due to anticipated interactions between crack bridging and stress-induced phase transformation. It has been found that these interactions produce a notable increase in toughness (K_(ss) approx = 13 MPa m~(1/2)) greater than the sum of the combination that would be provided separately by the two types of reinforcement.
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Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas (CSIC), C/Sor Juana Ines de la Cruz, 3, 28049 Madrid, Spain;