On the mechanics of braided composites in tension

An experimental investigation is reported on the uniaxial tensile behaviour of braided tubes, comprising glass fibres in an epoxy matrix. The failure mode switches from fibre fracture to neck propagation when the helix angle, defined as the angle between the fibre direction and the axis of the tube, exceeds about 45°. The observed neck geometry is used to deduce the evolution of deformation and damage within the matrix, and a work calculation is used to estimate the steady state neck propagation stress from a micromechanical model of braid deformation. A failure chart is constructed to show the effect of braid geometry on elastic modulus, yield strength, strain to failure and energy absorption of the braid.