The use of Digital Image Correlation in determining the mechanical properties of materials

The main purpose of this paper is to study the use of Digital Image Correlation in order to determine the Poisson's ratio in the case of aluminium alloy and composite materials under tensile tests. The satisfactory results obtained in the case of specimens made of aluminium alloy prove that Digital Image Correlation is able to satisfy the requirements in order to determine the Poisson's ratio. The testing procedure was carried out for two kinds of composite materials: (1) jute / epoxy composite material; (2) jute / glass / epoxy composite material. During the tests, a digital camera was used to capture the images of the tensile specimen during the tensile test. In order to measure both the longitudinal strain in direction of the tensile force and the transverse strain, the Digital Image Correlation method is used in the post-processing of all images recorded for each specimen. The data of transverse strain related to the longitudinal strain were graphically shown. The initial portion of curve corresponding to the linear portion of the stress-strain curve, was approximated by a linear regression function for each specimen tested. The slope of the fitting line represents Poisson's ratio. The Poisson's ratio, corresponding to the reinforcing plane with fabric for Jute / epoxy composite, is 35.5% greater than the corresponding to Jute / glass / epoxy composite.