Micro-mechanical properties and interfacial engineering of SiC fiber reinforced sol-gel fabricated mullite matrix composites

The toughening mechanisms of a SiC fiber reinforced sol-gel fabricated mullite matrix composites were studied by combining the microstructure, the micro-mechanical properties (especially the interface) and the macro fracture resistance by a bottom-to-upmechanical characterizationmethod (transmission electron microscopy, nano-indentation, fiber push-in, digital image correction, etc.). The results show a chemical-reaction controlled fiber/matrix interface in the as-fabricated composite, leading to pretty strong interfacial shear strength (similar to 537 MPa), measured by the fiber push-in tests. Interfacial engineering by chemical vapor deposited pyrocarbon interphase can effectively hinder the interfacial reactions and weaken the interfacial interactions. The low shear strength of the tailored fiber/matrix interface (similar to 155 MPa) could trigger the toughening mechanisms like interface debonding, fiber pull-out, etc., when the composite was subjected to external bending stresses. Finally, the fracture toughness of the novel composite was found significantly enhanced from similar to 0.8MPa root m to similar to 8.3MPa root m, after the interfacial engineering with pyrocarbon interphase. (C) 2017 Elsevier Ltd. All rights reserved.