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 promp ted the need for a full characterisation of their behaviour under dynamic l oading conditions. The strain rate effects of most unfilled polymers can be described by the Eyring theory of viscosity which assumes that the deforma tion of a polymer involves the motion of a chain molecule over potential en ergy 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 determ ine the effects of strain rate on the Poisson's ratio of the material. In a ddition, further tests were conducted at varying fibre contents to verify t he relationship between fibre content and Poisson's ratio. The findings fro m the experimental results suggest that Poisson's ratio is not sensitive to strain rate. In addition, it was suggested that the absence of rate sensit ivity 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 res erved.