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In this paper, a unit cell based micromechanical model is presented to predict the elastic-viscoplastic response of aligned short fiber titanium matrix composites subjected to combined axial loading in the presence of fiber/matrix interfacial damage. The effects of manufacturing process thermal Residual Stress (RS) are also included in the analysis. The representative volume element (RVE) of the short fiber composites consists of c×r×h cells in three dimensions in which a quarter of the short fiber is surrounded by matrix sub-cells. In order to obtain elastic-viscoplastic curves, the fiber is assumed to be linear elastic, while the matrix exhibits elastic-viscoplastic behavior. The Evolving Compliance Interface (ECI) model is employed to analysis interface damage. This model allows debonding to progress via unloading of interfacial stresses even as global loading of the composite continues. Results revealed that for more realistic predictions, in comparison with available experimental and the other models results, both interfacial damage and thermal residual stress effects should be considered in the analysis.

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In this paper, a 3D time dependent micromechanical model is presented to study the elastoviscoplastic behavior of aligned fiber reinforced composites in the presence of interfacial damage subjected to multi-axial loading. The representative volume element (RVE) of the composite consists of three phases including fiber, matrix and fiber/matrix interphase. The interphase is considered as a distinct phase with a definite thickness that covers the outer surface of fibers. The difference between of manufacturing process temperature to room temperature introducing thermal residual stresses is included in the analysis. The fiber and interphase are assumed to be elastic, while the matrix exhibits elastic-viscoplastic behavior with isotropic hardening. The Bodner-Partom viscoplatic theory is used to model the time dependent inelastic behavior of the matrix. The Needleman model is employed to analysis interphase damage. For metal matrix composites, it is shown that while predictions based on undamaged interphase are far from the reality, the predicted stress–strain behavior including interphase damage and thermal residual stresses demonstrate very good agreement with experimental data. Furthermore, the elastic properties of the composites with various aspect ratios are extracted by the micromechanical model. The elastic behavior predictions of the composite are also very close to experimental data and the other available model.