A method and a program for the automatic reconstruction and generation of 2D microstructures of composites based on the voxel array data has been proposed and implemented. Different methods of reconstruction and generation of finite element models of 2D microstructures of composite materials (geometry-based and voxel array based) are compared. With the use of the developed program, the deformation and damage evolution in composites with random and graded microstructures were numerically simulated. The tensile stress–strain curves, fraction of failed elements, and stress, strain and damage distributions at different stages of loading were determined for different random microstructures of the composites.