Multiphase and mesoscale analysis of the mechanical behavior of fiber reinforced concrete

Abstract

In recent years several laboratory tests have been employed to characterize the nonlinear behavior of composite materials, such as fiber-reinforced concrete (FRC). However, important stress-bridging mechanisms of the FRC structural elements are still under investigation. The acquired knowledge in the laboratory has supported the improvement of the numerical models for predicting mechanisms at the material scale and the load-displacement behavior of the composite. Therefore, the numerical models can be used to develop new advanced composite materials by predicting structural performance under different working conditions. This work proposes a mesoscale-multiphase approach to model FRC materials. The model considers four phases of the FRC material: coarse aggregates, mortar, interfacial transition zone (ITZ), and fibers. Mortar and aggregates are modeled using continuum elements with linear elastic behavior. Truss elements with an elastoplastic material model modeled randomly positioned fibers. Zero-thickness interface elements with a cohesive damage law are introduced at the interface between mortar elements and aggregates to represent the interfacial transition zone. The proposed model was validated by simulating direct tensile and three-point bending experiments. The numerical results of the load-CMOD curves are compared with an excellent agreement to experimental and numerical results reported in the literature. It also captures local cracking effects. Changes in fracture patterns were obtained when explicit fibers were introduced into the numerical model. Finally, this work provides a new methodology to investigate the fracture behavior of FRC structural elements considering an efficient strategy for explicitly modeling the fiber bridging effect by coupling fiber and cohesive finite elements. Comparisons between numerical models and experiments on FRC structural elements illustrate the proposed approach's efficacy.