Repair of Ceramic Matrix Composite Structures

The proposed Phase II research will build on a recent breakthrough development by MSNW, Inc. of a reinforced adhesive chemically compatible with oxide/oxide CMCs and demonstrating through thickness tensile strengths greater than 1 ksi. The Phase I projectdemonstrated the potential of this adhesive as the basis for a tailorable repair material. In the proposed Phase II research, two state-of-the-art CMCs, one from COI Ceramics and one from Boeing-Huntington Beach, will continue to be used as the basecom-posites. Reinforced adhesive materials containing chopped fibers or ceramic powders as discontinuous reinforcements and/or adhesive-impregnated Nextel 720 fabric plies as continuous reinforcements will be used to produce prototype field level repairsin damaged composite panels (Level 3 or Level 4 damage). The process will use a pressure-molding and low temperature drying and curing process followed by a final heat treatment in air. The repairs will be evaluated via mechanical testing at ambient andelevated temperatures both in the as-fabricated condition and after extended exposure at elevated temperatures. Failure modes will be evaluated by scanning electron microscopy microstructural examination and fractography. Dielectric properties of thebase composites and the repair materials will be evaluated to 2000,aF; emissivity properties to 2400,aF, both related to candidate applications. The project will target candidate applica-tions which include, but are not limited to, the DUST and X-37programs and possibly the SITE-M follow-on program. A demonstration component/subcomponent from the selected application will be damaged/repaired and provided to AFRL or its designee for independent evaluation. The Phase II project will be performed withengineering and testing assistance provided by Boeing-Huntington Beach and Boeing-St. Louis.