<p>The influence of fiber distribution on the mechanical response of unidirectional composites remains insufficiently quantified, particularly across a wide range of fiber volume fractions. This study develops a micromechanical finite element framework based on representative volume elements to compare the elastic behavior and crack initiation of composites with regular and random fiber arrangements from low to high fiber contents. Effective transverse elastic modulus, shear modulus, and Poisson’s ratio are evaluated using periodic boundary conditions and homogenization. Crack initiation is investigated using the extended finite element method coupled with matrix plasticity and cohesive modeling of the fiber-matrix interface. Results show that regular fiber arrangements yield higher transverse elastic modulus due to more uniform load transfer, whereas random distributions exhibit higher shear modulus and Poisson’s ratio as a result of fiber clustering, matrix-rich regions, and heterogeneous strain fields. Crack initiation occurs at lower global displacement in random microstructures, originating in highly stressed matrix ligaments between closely spaced fibers. Increasing fiber volume fraction accelerates crack initiation for both distributions. These findings demonstrate that fiber distribution strongly governs shear response and damage initiation, and that regular microstructural idealizations can underestimate crack initiation at high fiber contents.</p>