Processing of Non-Oxide Ceramic Matrix Composites: An Overview

2006 ◽  
Vol 50 ◽  
pp. 64-74 ◽  
Author(s):  
Roger R. Naslain
Keyword(s):  
Shear Stress ◽  
Thin Layer ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Oxide Ceramic ◽  
Matrix Composites ◽  
The Matrix ◽  
Low Shear Stress ◽  
Compliant Material ◽  
Low Shear

Ceramic matrix composites (CMCs) comprise a fiber reinforcement embedded in a ceramic matrix, the two main constituents being bonded through an interphase, which is a thin layer of a compliant material with a low shear stress, arresting and deflecting the matrix microcracks formed under load. Non-oxide CMCs, such as C/C ; C/SiC or SiC/SiC, are fabricated from a suitable precursor of the matrix, following a gaseous (CVI-process), a liquid (PIP and RMI processes) or a slurry (SI-HPS) routes. Each of these routes is briefly depicted focusing on fundamental aspects and its advantages and drawbacks discussed. Possible extensions of the processes to new composites are suggested. Finally, a comparison of these techniques, in terms of processability and composites properties is presented.

Micromechanics Approach for the Overall Elastic Properties of Ceramic Matrix Composites Incorporating Defect Structures

2020 ◽  
Author(s):  
Rajesh S. Kumar
Keyword(s):  
Elastic Properties ◽  
Volume Fraction ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Volume Shrinkage ◽  
Matrix Composites ◽  
Defect Structures ◽  
Linear Elastic ◽  
Elastic Tensor ◽  
The Matrix

Abstract Initial mechanical behavior of Ceramic Matrix Composites (CMCs) is linear until the proportional limit. This initial behavior is characterized by linear elastic properties, which are anisotropic due to the orientation and arrangement of fibers in the matrix. The linear elastic properties are needed during various phases of analysis and design of CMC components. CMCs are typically made with ceramic unidirectional or woven fiber preforms embedded in a ceramic matrix formed via various processing routes. The matrix processing of interest in this work is that formed via Polymer Impregnation and Pyrolysis (PIP). As this process involves pyrolysis process to convert a pre-ceramic polymer into ceramic, considerable volume shrinkage occurs in the material. This volume shrinkage leads to significant defects in the final material in the forms of porosity of various size, shape, and volume fraction. These defect structures can have a significant impact on the elastic and damage response of the material. In this paper, we develop a new micromechanics modeling framework to study the effects of processing-induced defects on linear elastic response of a PIP-derived CMC. A combination of analytical and computational micromechanics approaches is used to derive the overall elastic tensor of the CMC as a function of the underlying constituents and/or defect structures. It is shown that the volume fraction and aspect ratio of porosity at various length-scales plays an important role in accurate prediction of the elastic tensor. Specifically, it is shown that the through-thickness elastic tensor components cannot be predicted accurately using the micromechanics models unless the effects of defects are considered.

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