On the interaction between transformation toughening and crack bridging by ductile layers in hybrid composites

This paper presents the results of a combined theoretical and experimental study of toughening due to the combined effects of crack bridging ductile layers and particles that undergo stress-induced martensitic phase transformation in brittle matrix composites. The synergism that arises due to interactions between crack bridging and transformation toughening is discussed within the context of a micromechanics model. The synergism is shown to result in the potential for the design of hybrid composites with greater overall toughening levels than what can be achieved individually from each of the toughening mechanisms, i.e., crack bridging and transformation toughening. The theoretical model is validated for hybrid NiAl composites reinforced with ductile V layers and partially stabilized zirconia particles. The implications of the results are then discussed for the design of toughened brittle matrix composites.