60395 - Constituent and Ply Level Understanding of Electrical Resistance in Si-Containing Sic/sic Composites 

Electrical resistance, also known as direct current potential drop (DCPD), is being used to monitor damage evolution in SiC-based ceramic matrix composites. This technique can be utilized as a convenient nondestructive evaluation method for in situ damage detection. However, the electrical network in the composite system could be a challenging task due to the architecture complexity of the material and the variation of the constituent conductivity. 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, experimental and modeling of the resistance and change in resistance for different laminate architectures based on the nature of constituent content and orientation is needed to utilize and optimize electrical resistance as a health-monitoring technique. In this work, unidirectional, cross-ply and laminate composites fabricated with carbon containing “rods” have been analyzed as to resistance to develop a model for ply and constituent-based resistance properties. From this the change in resistance can be modeled for damage development and perhaps the architecture/constituent content can be tailored to create a “smarter” composite.