ABSTRACT
The determination of the stress-strain characteristics of a material up to failure is particularly useful as it gives information concerning important mechanical properties such as Young’s modulus, yield strength and brittleness. These parameters are vital in design considerations when the material is used in a practical situation. Stress-strain curves can be readily obtained for polymers by subjecting a specimen to a tensile force applied at a constant rate of testing. The stress-strain behaviour of polymers is not fundamentally different from that of conventional materials, the main difference being that polymers show a marked time or rate dependence (i.e. viscoelasticity). The situation can be simplified greatly by making measurements at a fixed testing rate, but it is important to bear in mind the underlying time dependence that still exists.
