Effect of Chemical Vapor Infiltration Induced Matrix Porosity on the Mechanical Behavior of Ceramic Matrix Minicomposites

Abstract

Ceramic matrix composites (CMCs) exhibit process-induced defects such as matrix porosity at multiple length scales that have a considerable influence on their mechanical and failure behavior. This work focuses on the microscale mechanical behavior of single tow CMCs in the presence of microporosities that exist within fiber bundles of the composite. Microporosities in a single tow C/boron nitride (BN)/SiC CMC minicomposite fabricated by chemical vapor infiltration (CVI) have been characterized by X-ray microcomputed tomography. The porosity distribution in the scanned region has been represented by probability distribution functions (PDFs) that serve as an input to numerical homogenization. Effective elastic properties in the presence of matrix micropores have been obtained by a two-step numerical homogenization approach considering the statistical distributions of pore parameters obtained from experimental characterization. A variation of the approach has been utilized to investigate the severity of pores with respect to their location and orientation relative to the fiber reinforcement.