Nonlinear mechanical and thermal responses of a unidirectional carbon-fibre-reinforced plastic

Abstract

Experimental results for unidirectional carbon-fibre-reinforced plastic (CFRP) are reported which show that the longitudinal stress-strain behaviour of this material is nonlinear elastic up to failure. The tangent modulus is found to reduce with increasing compressive strain, and to increase with increasing tensile strain. In addition, a small variation in Poisson's ratio with longitudinal strain is found. A specimen width of 5 mm (rather than the usually accepted 10 mm width) is used in order to reduce the likelihood of end effects being transmitted to the centre of the specimen. This is supported, to some extent, by a theoretical plane stress analysis using finite elements. A relatively simple method of measuring the thermal expansion of CFRP using suitably compensated strain gauges is described, and experimental results are given.