Phase-stepping photoelasticity for quantifying the interfacial response in fibre composites at fibre-breaks

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

“…These have been shown to significantly influence the matrix stress field and hence the magnitude of the interfacial shear stress which results from stress transfer into the unbroken fragments [3,6]. In this study, interfacial debonding was found to be initiated after matrix yielding and propagate along the fibre from the fibre-end, during fragmentation despite the lack of a fibre-surface treatment.…”

“…Since the maximum can be associated with the bonded interface we can see that at a high load, a debond forms and propagates along the fibre. The shear stress decays according to that of a well bonded fibre [6]. Fig.…”

“…More recently, Fiedler and Schulte [2] applied this technique to glass fibres in a resin. In recent studies, Zhao et al [3][4][5][6][7][8] have applied the four image phase-stepping automated photoelastic technique of Patterson and Wang [9] to single embedded fibres. This technique can provide full field maps of the relative retardation and the isoclinic angle.…”

“…By the application of an unwrapping algorithm [10], a continuous map of isochromatic fringe order can be obtained. It has been used to investigate the stress field in a matrix and the stress distribution at the interface in model composites [5,6,9]. In the previous studies, the photoelastic technique has been limited to relatively large diameter fibres of >80 lm because of the loss of light intensity through the optics and the high stress-fringe constant of the matrix resins.…”

“…Patterson and Wang [11] have developed a four image phase-stepping automated photoelastic camera for the simultaneous observation and recording of the four images required to solve the equations for quantification. Zhao et al [3,[5][6][7] succeeded in applying this technique to investigate the interfacial shear stresses in model single fibre composites. Full profiles of the interfacial shear stress could be determined by assuming that the principle stress at the interface is one of shear.…”