Development of Tensile Testing Methods for Quality Control Testing of Coated Ceramic Fibers

In order to make ceramic matrix composites (CMCs) into a useful class of materials for fabricating aerospace structures, there are several key issues that need to be resolved. One of these issues concerns the interaction between the interface coating and the fiber. The interface coating is key in controlling the crack deflection properties of the end composites. Current techniques used to analyze coatings provide have not proved useful in assessing whether the coated materials will yield good composites. At present, the only way to determine this is to actually make a composite and test it. The goal of this program is to develop a tensile testing method to quantitatively assess the interfacial shear strength between the fiber and the coating. This data should be useful in assessing whether a batch of coated material will yield a good composite material and will be a valuable quality control tool, significantly improving the manufacturability of CMCs. There are a number of issues associated with performing such measurements on coated fibers. This proposal identifies some of those shortcomings and addresses how they will be overcome. BENEFIT: Affordable, lightweight high-strength ceramic matrix composite materials could find use in a whole myriad of high-temperature applications, both military and commercial. The aerospace sector in particular would be well served in a number of applications by CMCs. Currently something of a niche market due to high cost, it is one whose growth is currently hindered by issues related to their manufacturability. The demand for these advanced materials will continue to grow as the cost is reduced.