Aspects Concerning the Transversal Contraction in the Case of Some Composite Materials Reinforced with Glass Fabric

Abstract

Abstract: The work presents the experimental determination of the transverse contraction coefficient i (Poissson's ratio) for three kinds of composite materials. For this purpose, it was used the digital image correlation method that is an optical method for the measuring of the deformations. The composite materials were made of the same epoxy resin but the reinforcement was different: reinforcement with glass fabric; reinforcement with oak wood flour; reinforcement both with oak wood flour and with glass fabric (hybrid composite material). The specimens were subject to tensile test and during the test, it was used the system Aramis 2M for image acquisition and their post-processing to determine both the longitudinal strain epsilon(y) (axial strain) on the direction of tensile loading and transversal strain epsilon(y) on the direction of the specimen width. The variations of the transverse strains epsilon(y) as a function of the axial ones for each specimen were graphycal represented. Then, the experimental data were approximated by linear regression that is by linear functions. The slopes of the straight lines represent Poisson's ratio v. It was found that the adding of the oak wood flour as filling material in case of the composite materials reinforced with glass fabric, leads to the increasing of the Poisson's ratio v.