Necking Behaviour Of Flattened Tubular Braided Composites

This paper presents results on the effect of braid angle and tow boundary conditions on the stress-strain behaviour of carbon fibre and epoxy-based braided composites under tension for braid angles. The specimens were produced by flattening the tubular braided sleeve during the preforming stage. The braid angle and tow continuity have a significant effect upon the pseudo-plastic and necking behaviour of the composites. Those specimens which showed extensive necking (all braid angles without cut edges and the 550 braid angle with cut edges) produced approximately the same specific energy absorption; specimens which showed either no, or very limited, pseudo-plasticity and necking, had low values of specific energy absorption. The addition of axial tow insertions can provide significant increases in the tensile properties (modulus and tensile strength) of the composites with continuous fibres while retaining significant pseudo-plasticity.