Accession Number : ADA269137

Title :   Pressureless Densification of Ceramic Matrix Composites.

Descriptive Note : Final rept. Mar 90-May 93,

Corporate Author : MISSOURI UNIV-ROLLA

Personal Author(s) : Rahaman, M. N. ; Dharani, L. R. ; Moore, R. E.

Report Date : 31 JUL 1993

Pagination or Media Count : 265

Abstract : The project produced a remarkable improvement in our understanding of how ceramic matrix composites densify and how they may be persuaded to reach high density by pressureless sintering. The key factors which hinder the sintering of ceramic matrix composites were determined and an innovative processing method for alleviating the sintering difficulties was developed. The method involves coating the reinforcement phase with a cladding of the matrix by chemical precipitation. The research formed the first reported study in which polycrystalline ceramic matrix composites containing an appreciable volume fraction of a reinforcement phase (up to 35 vol% particles or 25 vol% whiskers) were sintered to full density. The room temperature mechanical properties of the composites fabricated by pressureless sintering of coated powders were significantly better than those for similar composites fabricated from mechanically mixed powders. Pressureless sintering of a ceramic matrix with rigid inclusions was analyzed by a viscoelastic finite element method. The effects of inclusion volume fraction, inclusion shape, inclusion interactions and matrix packing were considered. The model predictions showed good agreement with the experimental data. Considerable potential exists for the application of the experimental and theoretical procedures developed in the project. Ceramic matrix composites, Sintering, Analytical modeling.

Descriptors :   *CERAMIC MATRIX COMPOSITES, *HIGH DENSITY, *EVOLUTION(DEVELOPMENT), CHEMICAL PRECIPITATION, CHEMICALS, CLADDING, COATINGS, EXPERIMENTAL DATA, INCLUSIONS, INTERACTIONS, MECHANICAL PROPERTIES, MODELS, PARTICLES, PHASE, POLYCRYSTALLINE, POWDERS, PRECIPITATION, PREDICTIONS, ROOM TEMPERATURE, SHAPE, SINTERING, TEMPERATURE.

Subject Categories : Laminates and Composite Materials

Distribution Statement : APPROVED FOR PUBLIC RELEASE