Ceramic Composite Mechanical Fastener System for High-Temperature Structural Assemblies

Hot structures fabricated from ceramic composite materials are an attractive design option for components of future high-speed aircraft, re-entry vehicles and propulsion systems to reduce weight and increase performance. One important detail in the design of such structures is that of joining and attachment. Large-area hot structures will likely be fabricated by mechanically joining smaller component sub-assemblies. Conventional metallic fasteners and fastening techniques do not provide structurally tight joints over a wide temperature range. A metallic fastener, which is snug at room temperature, will loosen at elevated temperature due to its relatively high thermal expansion. Excessive preloading at room temperature to maintain a tight joint at elevated temperature may be detrimental to the structural integrity of the joint. Ceramic composite fasteners on the other hand can be designed with near-perfect thermo-elastic compatibility with the adherends, however their prohibitively high cost to produce severely restricts their utility. The objective of this proposed program is to demonstrate the feasibility of a unique, cost-effective thermal stress-free ceramic composite mechanical fastener system suitable for assembly of high-temperature ceramic composite structures. The innovative fastener design facilitates joining load-bearing hot structural assemblies and can be produced at a cost much lower then other competing designs and methods. Ceramic composite fasteners will be produced and experimentally evaluated to determine the shear and tensile properties of the fasteners both individually and of respective lap-joined ceramic composite assemblies.