Evaluation of matrix and interface properties in SiC/SiC composites

Abstract

It has become increasingly important to characterize composite matrix materials in terms of processing-microstructure-property relationships. The characteristics of composite matrices can differ significantly from monolithic materials processed using more conventional techniques such as hot-pressing or sintering. Knowledge of the mechanical and thermophysical properties of the matrix as a function of processing parameters is necessary for the modeling and design of composite materials. In this study, the microstucture and mechanical properties of the matrix in the Nicalon/SiC composite system have been characterized as a function of processing temperature.The composites were fabricated by stacking multiple layers of plain-weave Nicalon fabric rotated in a 30°-60°-90° sequence within the cavity of a graphite holder. The preforms were then coated with carbon at 1375 K and 3 kPa. The coated preforms were densified using a forced chemical vapor infiltration (FCVI) technique developed at ORNL. The SiC matrix was produced by the decomposition of methyltrichlorosilane carried in hydrogen at temperatures of 1000, 1100, 1200, 1300, and 1400°C in order to reveal the effect of temperature on the properties of the composite and matrix.