Polymer composites are considered among the most promising materials for functional and structural applications. Improvement of mechanical properties of polymer composites using nanomaterials has generated much interest in recent years. This study aimed to predict the tensile strength and determine the damage mechanism of MXene-polyvinyl alcohol and MXene-epoxy composites. All parameters such as particle size, mechanical properties and interface layer strength were calibrated by finite element modeling with respect to experimental results. The influence of aspect ratio, volume fraction and MXene flake alignment on final mechanical properties of representative volume element models were investigated. Simulation results showed that aligned and higher aspect ratio particles significantly increase Young’s modulus and tensile strength of the composite. Compared with neat epoxy, a model with 30 vol% aligned MXene flakes resulted in increased Young’s modulus of 743% and tensile strength of 91.4%.