Constituent and Ply-Level Understanding of Electrical Resistance in Si-Containing SiC/SiC Composites

Electrical resistance (ER), also known as direct current potential drop, has been demonstrated as an enabling means to monitor damage evolution in SiC-based ceramic matrix composites (CMCs). For laminate composites, it has become apparent that the location and orientation of SiC fibers, free Si, and in some cases insertion of C rods can greatly affect the measured resistance. In addition, the nature of crack growth through the different plies which consist of different constituents will have different effects on the change in resistance. Therefore, both experimental and modeling approaches as to the resistance and change in resistance for different laminate architectures based on the nature of constituent content and orientation are needed to utilize and optimize ER as a health-monitoring technique. In this work, unidirectional and cross-ply laminate composites have been analyzed using a ply-based electrical model. Based on a ply-level circuit model, the change in resistance was modeled for damage development. It is believed that this can serve as a basis for tailoring the architecture/constituent content to create a “smarter” composite.