X-ray microtomography of ceramic and metal matrix composites

Abstract

Capabilities and limitations of X-ray computed microtomography (CT) in characterizing relevant composite material issues as identified during manufacturing processes were investigated. Damage in engine subcomponents was evaluated and compared with damage detected in pedigreed coupon type specimens. The system used is a newly developed state-of-the-art X-ray computed tomography system capable of providing digital radiography, computed tomography, and computed laminography. CT was found viable for characterizing processing defects and coating effect in thermally shocked carbon fiber reinforced silicon carbide matrix (C/SiC) samples. CT results from mechanically tested silicon carbide fiber reinforced reaction bonded silicon nitride (SiC/RBSN) matrix sample were evaluated and compared to engine tested SiC/RBSN turbine vanes. Thermomechanically cycled SiC (SCS-6) fiber reinforced Timetal 21S samples showed viability of CT in detecting composite constituents and limitations of CT in detecting matrix and fiber cracking. Also an engineering analysis approach was proposed to continuously integrate nondestructive evaluation modalities in the design-manufacturing-prototyping cycle of engine components.