Micromechanical models are presented which can be used to evaluate: stress concentrations in the vicinity of single and multiple fiber fractures in unidirectional composites under axial loading; the tensile strength of unidirectional composites; fiber coatings that can be used to maximize the transverse strain-to-failure and longitudinal shear strain-to-failure of composites; and the compression strength of composite materials containing embedded cylindrically shaped sensors or actuators. In each case, with the exception of the longitudinal shear model, the micromechanical predictions are compared with the experimental results. In the cases of the fiber fracture model and the transverse strain-to-failure model, these experimental results are obtained by employing a macro-model composite. It is demonstrated that the constituents of the macromodel composite can be systematically altered in order to study physical parameters such as fiber volume fraction and fiber coatings.