Elastic anisotropy in unidirectional fibre reinforced composites

Abstract

A theory is presented to calculate bounds on the elastic constants for unidirectional fibre reinforced composites, where the fibres and matrix both show transverse isotropy. This, and a more intuitive theory due to Brody and Ward (1971) tested using new comprehensive measurements for the elastic constants of a range of unidirectional composites using the ultrasonic immersion technique. These composites are based on epoxy resin reinforced either by glass fibres or with ultrahigh modulus polyethylene fibres and polyetheretherketone reinforced with carbon fibres (APC2). Agreement between experimental data and the theoretical bounds is very satisfactory considering the present uncertainties in some of the fibre elastic constants.