• Battley, Mark
• Newman, Roger
• Carpenter, James

Abstract

Composites reinforced with plant fibres suffer irreversible deformations under tensile loads. A new approach to characterising this behaviour combines multiple-loading experiments and calculation of derivatives of stress with respect to strain. This approach was assessed using composites made from unsaturated polyester reinforced with unidirectional flax yarns. The primary yield point was found at a strain of 0.17%,with additional minor yielding events to a strain of 1.0%and then linear deformation to failure at a strain of 1.9%. Irreversible deformation increased with stress and accounted for approximately half of the total deformation across the final half of the stress-strain curve. Analysis of deformation data showed that the elastic modulus was only slightly decreased by the accumulation of damage,despite irreversible deformations as large as 0.6%of the original specimen length. The specimens became stiffer after repeated loading,but failure stress remained unchanged.

Topics

• experiment
• stress-strain curve
• composite