Material Science
Prof. Satish V. Kailas
Associate Professor
Dept. of Mechanical Engineering,
Indian Institute of Science,
Bangalore – 560012
India
Chapter 12. Composites
There is a great need for materials with special properties with emergence of new
technologies. However, conventional engineering materials are unable to meet this
requirement of special properties like high strength and low density materials for aircraft
applications. Thus, emerged new class of engineering materials – composites.
Unfortunately, there is no widely accepted definition for a composite material. For the
purpose of this module, the following definition is adopted: any multiphase material that
is artificially made and exhibits a significant proportion of the properties of the
constituent phases. The constituent phases of a composite are usually of macro sized
portions, differ in form and chemical composition and essentially insoluble in each other.
Composites are, thus, made by combining two distinct engineering materials in most
cases; one is called matrix that is continuous and surrounds the other phase – dispersed
phase. The properties of composites are a function of the properties of the constituent
phases, their relative amounts, and size-and-shape of dispersed phase.
Millions of combinations of materials are possible and thus so number of composite
materials. For ease of recognition, composite materials are classified based on different
criteria like: (1) type of matrix material – metal matrix composites, polymer matrix
composites and ceramic matrix composites (2) size-and-shape of dispersed phase –
particle-reinforced composites, fiber-reinforced composites and structural composites. It
is understandable that properties of composite materials are nothing but improved version
of properties of matrix materials due to presence of dispersed phase. However, engineers
need to understand the mechanics involved in achieving the better properties. Hence the
following sections highlight the mechan