Investigation Into Debonding of Single Polypropylene Fiber Pullout in Concrete Using X-Ray Microtomography and Mechanically Regularized Digital Volume Correlation

To investigate the debonding process, an in-situ pullout experiment on an indented single polypropylene fiber was conducted using X-ray microtomography. This study utilized mechanically regularized global digital volume correlation (Reg-G-DVC) to measure the deformation fields of the fiber, matrix, and interfaces during interfacial debonding. Reg-G-DVC mitigates the impact of low contrast on measurement uncertainties, ensures the convergence of DVC calculations, and enables the element size to be reduced to improve the spatial resolution. The displacement jumps of the shared nodes between the fiber and the matrix were used to quantify interfacial debonding. The profiles of the normal and tangential components of the displacement jumps exhibited periodic features corresponding to the geometry of the indented fiber as it was pulled out. Additionally, the force-displacement curves displayed multi-peak fluctuations corresponding to the fiber geometry, thereby indicating that the periodic indentation of the fiber enhanced friction and the cohesive force between the fiber and the matrix during the pullout process. The displacement jumps along the fiber was maximum at the embedded initiation and decreased along the fiber toward the embedded end.