Flat glass fibres: the influence of fibre cross section shape on composite micromechanics and composite strength

Many of the fibres used in composite reinforcement have a non-circular cross section and recently non-circular glass fibre products have become commercially available. This paper explores the potential effects that such non-circular fibre shapes may have on the micro-mechanics of stress transfer at the fibre–matrix interface and the resulting changes in composite strength performance. Analytical modelling is used to show how the critical fibre length in composites with non-circular fibres is always less when compared to circular fibres with an equal cross sectional area. This can result in significant changes to the strength performance of discontinuous fibre reinforced composites. Additionally it is shown that non-circularity in fibre cross section can have important consequences for the use of single fibre micromechanical tests in the characterisation of interfacial strength.