Single fiber pushout tests are performed on model composites with carefully controlled interfacial surface placed in circular polariscope to observe the interfacial failure sequence. The high concentration of photoelastic fringes at the crack tip is used to identify debond initiation and to measure the crack length as the debond progressed. The numerical tool adopted in this study is a specially developed cohesive/volumetric finite element (CVFE) scheme based on an axisymmetric formulation of the quasistatic fracture problem. The numerical method combines conventional "volumetric" elements used to represent the mechanical response of the fiber and the surrounding matrix, and cohesive elements introduced along the fiber-matrix interface. Spontaneous failure is simulated with the aid of a quasi-linear cohesvie failure model describing the evolution of the interfacial cohesive elements. The results of the numerical simulations are compared with the experimental observations of fiber pushout obtained for the model composite systems. Since the friction coefficient, the process-induced residual stresses and the mode ll fracture toughness are extracted independently from the experimental results, only one parameter, the interface shear strength, is left to fit both the measured punch load vs. displacement curve and the observed evolution of the debond length. Excellent agreement is achieved between numerical and experimental results in both cases.
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