Six image phase stepped photoelasticity for the quantification of the stress field around 25 μm reinforcing fibres

A six image phase stepped photoelastic technique has been applied for the measurement of the interfacial shear stress distribution in the matrix resin along a reinforcing E-glass fibre of ∼25 μm in diameter at its end and at a fibre-break. Contour maps of the isochromatic fringe order and its corresponding isoclinic angle, which are related to the principal stress difference and direction relative to the fibre axis, could be obtained continuously using this photoelastic technique. Thus the actual interfacial shear stress along the fibre can be calculated. Furthermore in the presence of a fibre-break, interfacial debonding and matrix yielding during stress transfer was investigated. The micro-mechanics are shown to differ at a fibre-break compared to a fibre-end.