Development of Numerical Tool to Optimize the PyC Fiber Interface Coating in C/SiC Composites

Improved performance of Army missile systems depends in part on the development of advanced composite materials including ceramic matrix composites (CMCs). These material systems must be engineered for high strength, high toughness, low density, and high temperature capability. It is well understood that properties of CMCs have a large dependence on the behavior of the interface between the fibers and matrix. The key toughening mechanisms, including crack deflection and fiber pull-out, are controlled by the interfacial behavior. Any model that is developed to predict and optimize CMC properties must include this interfacial behavior as well as all constituent level damage that is experimentally observed. This Phase I program proposed by MR&D seeks to create a micromechanics-based tool that accurately models the interfacial region of CMCs and use that model to inform processing conditions for fabrication. The tool will be finite element based using commercial off-the-shelf software with user scripting to model some of the damage mechanics. In addition, through the use of subcontractors, MR&D will fabricate and test CMC materials with varying pyrolytic carbon (PyC) fiber interface coating thicknesses to validate the micromechanics tool. Finally, MR&D will optimize the interface parameters of the CMC material and perform a cost analysis to determine the potential reduction in cost resulting from the optimized fiber interface.