Tailored Extended Finite-Element Model for Predicting Crack Propagation and Fracture Properties within Idealized and Digital Cementitious Material Samples

Abstract

This paper presents a tailored extended finite-element model (XFEM) to predict crack propagation and fracture properties within idealized and digital cementitious material samples. The microstructure of the idealized cement-based materials includes the cement paste, particles, and interfacial boundaries. The tailored XFEM was developed to allow crack propagation within finite elements by using discontinuous enrichment functions and level-set methods. The Heaviside jump and the elastic asymptotic crack-tip enrichment functions were used to account for the displacement discontinuity across the crack-surface and around the crack-tip. The maximum fracture energy release rate was used as a criterion for determining the crack growth. The shielding effects within the interfacial zone were addressed with a numerical search scheme. The tailored XFEM was implemented with a MATLAB program to simulate the compact tension (CT) and the single-edge notched Beam (SEB) tests. For a homogeneous CT testing sample, the XFEM prediction on stress intensity factors was verified with the fracture mechanics analysis. The idealized samples of cement-based materials were generated with varied microstructures, including particle locations, orientations, and shape factors. The tailored XFEM was applied to investigate the effects of these microparameters on the fracture patterns of the idealized samples under CT loading. The XFEM simulation was also conducted on a homogeneous offset-notched SEB sample to predict the mixed-mode crack propagation. The predicted crack path matches well with refined cohesion fracture modeling from a recent study. Further validation of the tailored XFEM was conducted with fracture simulation of a digital SEB sample generated from the actual tested specimen. The predicted crack path was favorably compared with the fracture pattern of the tested concrete specimen with a middle notch. These simulation results indicated that the tailored XFEM has the ability to accurately predict the crack propagation and fracture properties within idealized and digital cementitious material samples.