A New Brazilian Disc Test Procedure for the Elastic Moduli of Orthotropic C/C-SiC Composites

Background

Advanced ceramic matrix composites (CMC) are aimed at highly demanding thermo-mechanical environments, such as space or hypersonic applications. Their design and manufacturing require a reliable, cost-effective method for estimating and quantifying CMC mechanical properties.

Objective

CMC composite materials present orthotropic mechanical properties. Different tests are often conducted to measure all independent elastic properties. These variety of tests are expensive and demand significant time and effort. Therefore, it is highly desirable to have one mechanical test that can generate all or most of the elastic properties.

Method

This study proposes a single Brazilian disc (BD) test setup. It investigates an efficient inverse problem to evaluate the Young’s and shear moduli of an orthotropic Liquid Silicon Infiltrated (LSI) C/C–SiC CMC. A combined BD test and Digital Image Correlation (DIC) technique were used for this purpose. The BD test employs a circular disc compressed diametrically in varying orientations of the tested multi-layered CMC 0°/90 ^o woven carbon fibers. The BD introduces a multi-axial stress and strain field highly affected by these primary elastic moduli. DIC enables full-field multi-axial strain calculations in large spatial variations.

Results

A numerical study resulted in a unique iterative inverse-mechanics test procedure based on BD tests conducted on orthotropic materials at two material orientations. This approach was applied to measure C/C-SiC material properties, showing an efficient and reliable appraisal of major elastic moduli.

Conclusions

The presented approach may drive down both the duration and cost of the mechanical evaluation, thereby potentially improving future process designs.