A modified analytical model for the single-fiber pullout problem involving non-classical stress–strain relationships due to residual stresses: Analysis of stress field in the fully bonded region

Abstract

Upon reevaluating the influence of residual stresses generated by thermal mismatches in fibrous composites during the curing process, we introduce a modified model for the extraction of a single fiber from an elastic matrix. In contrast to previous models, which solely factored residual stress effects into the boundary conditions at the fiber–matrix interface while omitting them from the constitutive relations, our current model acknowledges bulk residual stress as finite values. Consequently, it yields non-conventional constitutive relations to describe the incremental deformation caused by external pulling forces. We have developed a practical semi-analytical series solution for the radial displacement of the matrix and an exact solution for the radial displacement of the fiber. To validate our modified model, we simplify it to a scenario where the influence of residual stress on the stress–strain relationship is excluded and compare it with results from existing literature. This comparison underscores the soundness of our modified model. We present a phase diagram to illustrate how the impact of residual stress on stress field prediction varies based on the ratio of the fiber modulus to the matrix modulus. This phase diagram serves as a valuable tool for evaluating whether it is advisable to transition from the previous mechanical model, which disregards the influence of residual stress on the stress–strain relationship, to the new model, which takes this influence into account within the stress–strain relationship.