Development of Capability for Characterization of Ceramic/Ceramic Composites. Part 1. Effects of Reinforcement Geometry on the Mechanical Properties of SiCw/Al2O3 Composites and Prediction of Flexural Properties by Energy Method
Abstract
The mechanical properties of ceramic composites change due to variations in the size and geometry of the reinforcement. In the present work the effects of SiC whisker (SiCw) and SiC platelets (SiCp) have been investigated on the mechanical properties of SiC/Al2O3 composites. The flexural properties of both whisker- and platelet-reinforced SiC/Al2O3 composites were measured using the four-point bend test. Fracture toughness was determined for both straight and chevron notched specimens. Scanning electron microscopy examination of the fractured surfaces was conducted to perform failure analyses and understand toughening mechanisms. The results of the investigation indicate that SICw/Al2O3 composite provides higher flexural strength and fracture toughness compared to SiCp/Al2O3 composite. During the hot pressing, the control of the orientation of the SiCp is extremely difficult and it appears to form a porous matrix structure which substantially lowers the strength. Moreover, low l/d ratio of SiCp has a major influence on the fracture toughness. Attempts have been made to predict the flexural properties of the composite by coupling the principle of minimization of potential energy and the rule of mixture. The deflection curve of a composite four-point beam coupon is found from an assumed Fourier series solution satisfying the geometric boundary conditions and using the rule of mixture. Strain compatibility conditions are applied to determine the axial displacement field and hence the flexural strain. Stresses on the matrix and fiber are then estimated under the assumption of isostrain conditions.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1991
- Accession Number
- ADA251319
Entities
People
- A. Haque
- Hassan Mahfuz
- Shaik Jeelani
- Sirajus Salekeen
Organizations
- Tuskegee University