Micromechanical damage analysis in laminated composites with randomly distributed fibers

Damage mechanisms in uni-directional fiber-reinforced plastics have been studied at the micro-scale by developing three-dimensional-repeating unit cells with randomly distributed fibers. Three damage mechanisms have been considered, viz., matrix damage, fiber failure and fiber-matrix interface debonding. The development of these damage modes and their effect on the overall stress-strain response of the micro-structure due to varying fiber volume fractions, loading conditions (longitudinal, transverse and combined transverse tension and shear), spatial distribution of fibers and fiber strength distributions (deterministic and Weibull) are of interest. A numerical framework has been developed that allows for conducting such studies for the chosen parameters. Microscopic images of real micro-structure of uni-directional fiber-reinforced plastics have been used to develop the random micro-structure for the three-dimensional-repeating unit cell. In the longitudinal loading scenario, fibers with Weibull strength distribution are closer to reality. While the three-dimensional-repeating unit cell under longitudinal loading fails in predominantly fiber failure mode, debonding and matrix damage play a major role in determining the average response of the micro-structure under transverse and combined transverse and shear loading