Uniaxial compression analysis of glassy polymer networks using digital image correlation

Analytical methods which apply digital image correlation (DIC) to study the strain behavior of glassy polymer networks in uniaxial compression are presented. This non-contact technique generates accurate and reproducible data for analyzing compression modulus, Poisson's ratio and yield strain. DIC eliminates the need for extensometers or strain gauges, and provides a substantial increase in accuracy for measuring strain compared to a LVDT. DIC allows for simultaneous longitudinal and transverse strain measurements to calculate Poisson's ratio, and is particularly sensitive for measuring small strain compression modulus of glassy solids. DIC techniques are useful for studying the pre-yield, yield and post-yield behavior of glassy polymer networks and provide insight of the non-uniform strain behavior of these materials prior to yielding. An accurate yield strain was obtained using DIC which clearly eliminated any erroneous strain data associated with fixture and equipment compliance. Finally, DIC allowed for the calculation of true compression stress and true compression strain of glassy polymers. (C) 2010 Elsevier Ltd. All rights reserved.