Numerical analysis and investigation of short- and long-term behavior of unidirectional composites

This study gives a detailed analysis on estimating the ultimate tensile strength of unidirectional fiber reinforced composites and its creep behavior under sustained tension load. We develop two different micromechanical models that allow us to estimate the longitudinal tensile strength and the evolution with time of fiber and matrix stresses around arbitrary array of fiber breaks. The first model is based on the shear-lag theory while the second one is developed using the software Abaqus. The comparison of the above models allowed to validate the fundamental assumptions of the shear-lag theory (first model) as well as several numerical issues related to time integration and spatial discretization. The Monte–Carlo method was used in order to account for the stochastic fiber strength and its impact on the ultimate tensile strength (short-term) and creep (long-term behavior) of unidirectional composites. Finally, a parametric investigation on the fiber type and the load level on the long-term behavior of unidirectional composites was performed showing an accelerating creep effect for fibers of inferior quality such as glass fibers compared to carbon fibers.