Bending behaviour of laminated knitted fabric reinforced beams

Abstract

Four-point bending tests have been performed for the laminated beams reinforced in an epoxy matrix with six layers of knitted carbon fibre fabrics arranged in different orientations. It is seen that only partial layers of the beams have failed after the bending tests. The failures of all the beams were initiated from their bottom surface, i.e. due to an excessive tensile stress. Thus the failures were resulted from the matrix tensile fracture, as the epoxy tensile strength is lower than its counterpart in compression. The present experimental evidence suggests that only the use of a stress failure criterion is not sufficient in the layer-by-layer modelling for the ultimate strength of a laminate when a lateral load is involved. A critical deflection/curvature condition is also necessary.