On the mechanical properties, deformation and fracture of a natural fibre/recycled polymer composite

Abstract A composite laminate based on natural flax fibre and recycled high density polyethylene was manufactured by a hand lay-up and compression moulding technique. The mechanical properties of the composite were assessed under tensile and impact loading. Changes in the stress–strain characteristics, of yield stress, tensile strength, and tensile (Young's) modulus, of ductility and toughness, all as a function of fibre content were determined experimentally. A significant enhancement of toughness of the composite can be qualitatively explained in terms of the principal deformation and failure mechanisms identified by optical microscopy and scanning electron microscopy. These mechanisms were dominated by delamination cracking, by crack bridging processes, and by extensive plastic flow of polymer-rich layers and matrix deformation around fibres. Improvements in strength and stiffness combined with high toughness can be achieved by varying the fibre volume fraction and controlling the bonding between layers of the composite.