Observation of fiber-matrix interfacial stresses using phase-stepping photoelasticity

Abstract

In this study, the single fiber composite was used to evaluate the stress transfer between a single fiber and a matrix. Single steel fiber was inserted to the epoxy resin, and it was applied the tensile load. Applied load was from 0 N to 177 N, and then the photoelastic images were taken by a digital CCD camera. In the photoelastic analysis, the phase-stepping and phase-unwrapping technique were used to measure the stress difference distribution more accurately. Obtained data were included the 3D information, therefore, we converted the stress difference data, including the 3D information to 2D photoelasticity using the geometrical information. The maximum shear stress was placed on the side surface of the steel fiber near the end of fiber, and the maximum normal stress difference was measured near the surface of the end of the fiber. The results of stress distribution on the interface between the fiber and the resin indicated that the stress concentration was observed in the middle part of the end of the fiber and the side surface near the end of the fiber.