ABSTRACT
Given the choice of using rubber or steel to construct a permanent road bridge, we are all likely to opt for steel. Someone will have made a choice like this for many of the products and engineering structures that we use, and different solids have many different types of properties which enable them to be used in a wide variety of applications. The mechanical properties of solids reveal how they behave when a stress is applied to them. The relationship between stress and strain for a particular material can be plotted as a stress–strain curve, which shows a hypothetical stress–strain curve for a metal being subjected to a tensile stress. Like alloys, composite materials combine the properties of two or more materials when no single material is up to the job. There are several tests for measuring hardness.
