Bending failure of aramid fibre-reinforced composite

Flexural failure of a unidirectional aramid SVM/epoxy composite was studied using two-point loading of half-ring specimens. Failure originated near the compressive side of the specimen where several intersecting shear yield bands, similar to slip bands in metals, were observed. The angle between the yield bands and the loading direction was45 ± 2°. The thickness of the yield bands grew proportionally to the shear displacement of their opposite sides. The yield stress of the SVM fibres in bending was equal to 500 MPa, which is close to the fibre strength in pure axial compression of 400–450 MPa. The maximum failure stress of the composite in bending, 530 MPa, was approximately twice as high as the strength of the composite under pure axial compression (260–280 MPa). In bending the composite is elastic in the tensile part of the beam whilst the other, compressed, part is elastic-plastic.