Page 24 - Mechanics Analysis Composite Materials

Chapter 1. Introduction 9
Solids that deal with equations derived for infinitesimal volumes of material. And
third, this allows us to simplify the strength and stiffness evaluation problem and
to reduce it to a reasonable practical level not going into analysis of the actual
mechanisms of material deformation and fracture.

1.2. Composite materials

This book is devoted to composite materials that emerged in the middle of the
20th century as a promising class of engineering materials providing new prospects
for modern technology. Generally speaking any material consisting of two or more
components with different properties and distinct boundaries between the compo-
nents can be referred to as a composite material. Moreover, the idea of combining
several components to produce a material with properties that are not attainable
with the individual components has been used by man for thousands of years.
Correspondingly, the majority of natural materials that have emerged as a result of
a prolonged evolution process can be treated as composite materials.
With respect to the problems covered in this book we can classify existing
composite materials (composites) into two main groups.
The first group comprises composites that are known as “filled materials”. The
main feature of these materials is the existence of some basic or matrix material
whose properties are improved by filling it with some particles. Usually the matrix
volume fraction is more than 50% in such materials, and material properties, being
naturally modified by the fillers, are governed mainly by the matrix. As a rule, filled
materials can be treated as homogeneous and isotropic, i.e., traditional models of
Mechanics of Materials developed for metals and other conventional materials can
be used to describe their behavior. This group of compositesis not touched on in the
book.
The second group of composite materials that is under study here involves
composites that are called “reinforced materials”. The basic components of these
materials (sometimes referred to as “advanced composites”) are long and thin fibers
possessing high strength and stiffness. The fibers are bound with a matrix material
whose volume fraction in a composite is usually less than 50%. The main properties
of advanced composites due to which these materials find a wide application in
engineering are governed by fibers whose types and characteristics are considered
below.
The following sections provide a concise description of typical matrix materials
and fiber-matrix compositions. Two comments should be made with respect to the
data presented in those sections. First, only a brief information concerning material
properties that are essential for the problems covered in this book is presented there,
and, second, the given data are of a broad nature and are not expected to be used in
design or analysis of particular composite structures. More complete description of
composite materials and their components including the history of development and
advancement, chemical compositions, physical characteristics, manufacturing, and
applications can be found elsewhere (Peters, 1998).