A Phase‐Field Framework for Rate‐Dependent Failure in Polymer Fiber‐Reinforced High‐Performance Concrete

ABSTRACT High‐performance concrete (HPC) is characterized by its improved strength and durability when compared to normal concrete. However, it still exhibits brittle failure, prompting the use of fiber reinforcement to enhance their post‐cracking performance. Steel fibers are commonly used for this purpose, but their susceptibility to corrosion in harsh environments, high density, and elevated energy footprint can render them less suitable. In contrast, polymer fibers offer a more sustainable alternative, combining corrosion resistance with a density significantly lower than that of steel. Nevertheless, the intrinsically viscoelastic mechanical response of polymer fibers, the influence of environmental agents and loading magnitude as well as their impact on the failure of fiber‐reinforced concrete remain insufficiently understood. This study extends a phenomenological phase‐field fracture model to investigate the effect of fiber orientation on the structural response of polymer fiber‐reinforced HPC. To describe the fiber reinforcement, the model incorporates a nonlinear viscoelastic formulation based on the Schapery model. In order to capture the failure in tension and compression of HPC, the step‐wise linear degradation functions are used. Furthermore, various orientation distribution functions (ODFs), accommodating different fiber orientations, are implemented. The model is solved using staggered approach and the boundary value problem is based on the EN 14651. Thus, the sensitivity of the pure HPC case to the number of cycles in the staggered scheme is assessed. Then, the finite element analyses are carried out under different loading rates. Finally, the performance of the numerical model is discussed using Load vs . CMOD (crack mouth opening displacement) curves.