Exploration of the fracture mechanism of UHPFRC by acoustic emission, DIC and magnetoscopy testing

This paper investigates the fracture mechanism of ultra-high-performance fiber-reinforced cementitious composites (UHPFRC) using acoustic emission (AE), digital image correlation (DIC), and magnetoscopy testing. Four specimens undergo uniaxial tensile loading, preceded by magnetoscopy testing to determine local fiber volume and orientation. DIC captures matrix discontinuities, crack initiation, and propagation. Acoustic emission monitors fracture mechanisms at different loading phases. During the elastic phase, matrix discontinuities and fiber debonding are observed to occur. A higher density of matrix discontinuities during this phase enhances hardening behavior and tensile performance. The softening phase of UHPFRC is found to be characterized by three stages based on AE parameters: emergence and competition of multiple fictitious cracks, propagation of a dominant fictitious crack, and real crack formation. The rate of dominant fictitious crack propagation can be determined by analyzing the evolution in AE parameters with stress decrease. Uniform fiber distribution limits the initiation and propagation of fictitious cracks.