Multiscale modeling of the viscoelastic response of braid-reinforced polymers: Model formulation and experimental assessment considering different rheological models

Abstract Multiscale modeling is routinely employed to obtain the effective properties of hierarchically-organized materials. Departing from the definition of observation scales, upscaling is employed to obtain the effective (homogenized) properties at each scale. In this paper, unit-cell based upscaling procedures are used for homogenization, providing the basis for a multiscale model for the viscoelastic behavior of braid-reinforced composites. Elastic fiber and viscoelastic matrix properties are upscaled over three distinct observation scales, accounting for yarn and braid geometry. Two rheological models, i.e., the fractional Zener model and the extended Lomnitz model are employed to describe the viscoelastic matrix behavior. The proposed multiscale model is experimentally validated by compressive creep tests on braid-reinforced tubes, with the model results agreeing well with the experimentally-obtained results. Moreover, the experimentally-observed influence of the braid geometry is correctly reproduced by the proposed multiscale model, providing access to the sensitivity of geometrical properties on the mechanical performance of braid-reinforced polymers.