Effects of IR Thermography-Detected Defects on Performance of SiC/SiC Composites

In order to utilize the promising high temperature characteristics of ceramic matrix composites (CMCs) in applications such as Joint Strike Fighter (JSF) engine components, the effects of potential defects must be sufficiently understood and characterized. The use of CMCs in engines provides reduction in cost and weight, while still providing high strength, more durability, and high temperature capabilities. The combination of these leads to a significant increase in performance of an engine. The ability of engine components to withstand higher temperatures also leads to higher thrust capabilities. Under this program, infrared (IR) thermography will be used for the non-destructive evaluation (NDE) of SiC/SiC panels to investigate defects. The ability for IR thermography to be used as a field technique makes it an excellent choice of NDE for this application. Through testing and finite element analysis, virgin panels and panels manufactured with representative artificial defects will be evaluated to assess the structural effects that defects have on the material. Manufacturing defects such as delaminations and porosities will be investigated in addition to in-service defects that are applicable to CMC engine components. BENEFITS: The overall goal of the Phase I and Phase II SBIR program is to develop and demonstrate the feasibility of identifying and evaluating defects in CMC engine parts. Phase I of this program will generate a method for identifying and evaluating defects in representative CMC coupons. Trade studies will be performed to determine the best modeling methods for analyzing NDE methods for defect identification and correlating test data used for defect evaluation. The successful completion of Phase I and Phase II will result in the application of this new technology to a representative engine flap subcomponent with several representative complex geometries. Defects such as delaminations, high porosity regions, and joint micro-cracking will be intentionally incorporated during fabrication. The subcomponent will have gone through a thorough testing program including structural and dynamic testing. Developments and results from Phase I activities will allow for accurate pre-test predictions on the structural performance of the CMC structure with defects. IR thermography will be conducted intermittently throughout the test program to assess any growth of the defects.