Measurement of micro stress fields in epoxy matrix around a fibre using phase-stepping automated photoelasticity

The stress field in an epoxy resin matrix near the broken-end of a glass fibre was measured using a phase-stepping automated polariscope. Fringe order contour maps were obtained continuously in a region of 1.835×1.835 mm using this photoelastic technique. Principal stress difference, at any point in the matrix near the fibre-matrix interface and the fibre-end, could be calculated. The present technology enables continuous fringe contours and the distribution in principal stress difference around a fibre-end with partial debonding or a matrix crack to be obtained. Thus the effects of debonding and a transverse crack, emanating from a fibre-break, on the matrix stresses have been fully described.