3D Braid CMC Fasteners

Ceramic Matrix Composites (CMCs) are attractive for propulsion applications due to their potential for higher temperature capability, weight reduction, and durability improvements. However, CMCs present design challenges due to their anisotropic properties, generally low interlaminar shear strength, low bearing strength, limited strain tolerance, and their reaction with alloy components at CMC/alloy interfaces. Currently the prevalent mode of joining CMC to metals is to use metallic fasteners. Since the CMC component has lower Coefficient of Thermal Expansion (CTE), and bearing strength, it is desirable to use CMC fasteners for the attachments. The current baseline for a CMC fastener is the Miller fastener, which is a 2D, laminated CMC design with a rectangular cross-section. It is susceptible to stress concentrations at the corners and failure due to delamination. As such, it has not found wide acceptance in the industry. In this topic a 3D braided solution is sought which can be fabricated to near net-shape. This will eliminate delamination as a potential failure mode and reduce scrap during production.