Evaluation Tools to Measure Surface Quality and Chemistry of Carbon-Carbon Composites and Coatings

A suite of nondestructive evaluation (NDE) techniques is proposed for monitoring the condition of high temperature carbon-based ceramic matrix composite (CMC) materials during manufacturing. Measurements of surface roughness, microstructural makeup, and chemical species will be performed in real time using a laser source that is common to two of the three techniques and noncontact optical detection. Surface roughness and chemical species composition can be measured simultaneously using interferometric methods and Raman scattering, respectively. The measurements will be made at a point that can be scanned across the specimen with instrumentation that is integrated into the manufacturing system. Microstructural features can be monitored simultaneously as well using a complementary technique, optical coherence tomography (OCT). The proposed feasibility study will permit three interferometric methods for surface roughness to be evaluated, enabling down selection of the optimum technique. Feasibility will also be evaluated for Raman scattering to determine species composition and OCT to determine microstructural features.