Damage-Based Modeling of Fiber Pullout under Variable Compressive Stress

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Abstract
When steel fibers are pulled out from a cementitious matrix, the interfacial friction decreases with sliding distance. The frictional decay is a function of the far-field lateral stress. In this paper, a damage model is developed to derive the interfacial friction in terms of the sliding distance as well as the lateral compression history. The model assumes the interfacial friction to be governed by two related parameters: the interfacial residual stress τi0 (reflecting the fiber/matrix misfit) and the interfacial friction coefficient μ¯ (reflecting the surface asperity). This work shows experimentally that for a given interface, a unique relationship, independent of sliding distance and lateral compression history, exists between τi0 and μ¯. Based on this observation, a damage model, which evaluates the interfacial residual stress τi0 only, is developed to predict the pullout curves under variable lateral compressive stress. An approach to account for material variability from one batch of specimens to a...