SEDL / STP / STP1169-EB / STP17983S

Internal Friction in Silicon-Carbon/Glass Ceramic Composites

Rivière, A
Professor and director, Laboratoire de Mécanique et Physique des Matériaux, U.R.A.C.N.R.S., Poitiers,

Woirgard, J
Professor and director, Laboratoire de Mécanique et Physique des Matériaux, U.R.A.C.N.R.S., Poitiers,

Pages: 10    Published: Jan 1992

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Abstract

Composite materials composed of a glass-ceramic matrix and silicon-carbon (SiC) fibers have been recently developed for high-temperature applications.

In the present work, damping properties and the dynamic modulus of unidirectional composites made with SiC-Nicalon fibers and aluminum silicate based matrix (glassy or partially recrystallized) have been studied in a variable frequency torsion pendulum over wide temperature and frequency ranges.

A relaxation peak, characteristic of the vitreous phase, has been observed in specimens with different ratios of the recrystallized phase. The apparent activation energy (Hp = 1.24 eV) and the limit relaxation time (τ0 = 2.10^-16s) were found to be constant for all samples.

On every specimen, a decrease of the peak width, accompanied by an increase in the relaxation strength, was observed for measurements at increasing temperatures.

In glassy matrix specimens, the low-frequency damping background has been found to increase abruptly. In the partially crystallized composite specimens, a peak caused by the glassy transition superimposed on to the high-temperature background was also observed.