Microscale mechanical behaviour of ceramic matrix composites considering processing e ects

Abstract

The current work explores the phenomenon of microscale damage mechanism driven quasi- ductile behaviour of C/BN/SiC ceramic matrix composite (CMC) at the microscale focusing on process-microstructure-property correlations. C/BN/SiC minicomposites have been fabri- cated by chemical vapour infiltration (CVI) with varying interphase thicknesses and constituent volume fractions by varying the interphase (BN) and matrix (SiC) in filtration durations. The effect of processing durations on the resulting microstructure, tensile response and damage mechanisms up to and during ultimate failure of CMC minicomposites have been obtained ex- perimentally that highlight the significant infuence of processing duration on the tensile and failure behaviour of CMC minicomposites. Processing induced micro-scale matrix porosity in the fabricated minicomposites has been characterized by X-ray micro-computed tomography. Effective elastic properties in the presence of matrix micro-pores have been obtained by a two-step numerical homogenization approach that includes the statistical distributions of pore parameters obtained from experimental char- acterization. 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. A probabilistic progressive damage modeling approach has been proposed to predict the tensile response of CMC minicomposites considering the microstructural information from fab- ricated minicomposites. The highlight of the proposed numerical approach is the development of a 3 phase shear lag model to better approximate matrix crack driven stress transfer in the presence of an interphase between the ber and the matrix. The in uence of volume frac- tions, constituent properties and interfacial properties on the mechanical behavior of CMC minicomposites have been presented. The presented approaches and results provide an insight into the processing-microstructure- tensile response relationship and the e ect of processes induced defects on the tensile response in CMCs. Additionally, modeling approaches have been proposed for predicting the tensile response of CMCs at the microscale considering processing induced defects.