The role of twist and crimp on the vibration behaviour of flax fibre composites

The damping properties of unidirectional, 0/90 and twill 2/2 flax fibre (FF) reinforced epoxy composites containing 40 vol% of fibres have been measured by vibration beam testing (VBT). The influence of the impregnation quality, the fibre/matrix adhesion, the quality of the fibres, the twist of the FF yarns and the crimp in the FF fabrics on these properties was quantified. Carbon and glass fibre reinforced epoxy composites were considered as comparison. Unidirectional FF instead of glass fibres led to a damping increase of 133%. Under the VBT conditions, the inter and intra-yarn frictions mechanisms were dominant leading to energy dissipation. The damping properties increased with the twist and crimp amount, leading to a damping increase of 79% when a twill 2/2 fabric was considered instead of a [0/90]n laminate. Fibre/matrix friction improved the damping properties by 23% with a limited fibre/matrix adhesion. Finally damping maps for several material systems were established.