The effect of strain rate and fibre content on the Poisson's ratio of glass/epoxy composites

The utilisation of composite materials in structural applications has prompted the need for a full characterisation of their behaviour under dynamic loading conditions. The strain rate effects of most unfilled polymers can be described by the Eyring theory of viscosity which assumes that the deformation of a polymer involves the motion of a chain molecule over potential energy barriers. The Eyring model suggests that yield stress varies linearly with the logarithm of strain rate. In the present study, tensile tests were performed on a glass epoxy laminate at different rates of strain to determine the effects of strain rate on the Poisson's ratio of the material. In addition, further tests were conducted at varying fibre contents to verify the relationship between fibre content and Poisson's ratio. The findings from the experimental results suggest that Poisson's ratio is not sensitive to strain rate. In addition, it was suggested that the absence of rate sensitivity in the Poisson's ratio of the laminates rested is due to the presence of fibres in the composites. (C) 1999 Elsevier Science Ltd. All rights reserved.