AN OVERVIEW OF CERAMIC MATRIX COMPOSITES

Abstract

Ceramic matrix composites are materials in which one or more distinct ceramic phases are intentionally
added to another, in order to enhance some property that is not possessed by the monolithic ceramic materials. In
ceramic matrix composites, a given ceramic matrix is reinforced with either discontinuous reinforcement, such as
particles, whiskers or chopped fibers or with continuous fibers. The basic reinforcements which are included in the
ceramic matrices are carbon, glasses, glass-ceramics, oxides and non-oxides. The main function of the matrix is to keep
the reinforcing phase in the desired orientation or location and act as a load transfer media as well as protect
reinforcement from the environment. Whereas, the primary aim of the reinforcement is to provide toughness to an
otherwise brittle matrix. Filler materials in particle form are also sometimes added to the matrix materials during the
processing of CMCs to enhance the properties such as electrical conductivity, thermal conductivity, thermal expansion
and hardness. Particles with different shapes such as spherical, irregular and faceted are commonly used during the
processing of CMCs. Ceramic matrix composites (CMCs) can be processed either by conventional powder processing
technique or by other more specific and customized techniques. The processing temperature for CMCs is extremely high
compared to polymer or metal matrix composites which leads to a very difficult and expensive processing. Moreover,
ceramic matrix composites are widely used in several engineering applications such as in heat shield systems, gas
turbines components such as combustion chambers, stator vanes and turbine blades, rocket engines, components for
burners, flame holders, hot gas ducts, brake disks and brake system components for airplanes or cars which experience
extreme thermal shock, bearing components that necessitate high corrosion and wear resistance. Ceramic materials
possess high strength and modulus at elevated temperature. But their use as structural components is severely limited
because of their brittleness. The continuous fiber rein forced ceramic-matrix composites (CMCs),by incorporating fibers
in ceramic matrices, however, not only exploit their attractive high-temperature strength but also reduce the propensity
for catastrophic failure. In this paper presents an over view and study on ceramic matrix composites of the role of
oxidation in time-dependent response, properties of hexagonal boron nitride and fatigue behaviour of SiC composites