Moiré Interferometry Analysis of Fiber Debonding

Progressive fiber debonding in steel fiber/cementitious matrix composites has been studied using a single fiber pullout test that permits simultaneous measurements of the load versus crack opening displacement relationship and Moiré interferometry fringe patterns. Analysis of Moiré interferometry patterns allows the fiber axial and interfacial shear stresses to be calculated along the entire fiber length. The interfacial shear stress distribution along the debonded length of the fiber indicates a steep decrease in shear stress with interfacial slip, from 6 to 1 MPa for 7 µm of fiber slip and a crack opening displacement of 22 µm. These results suggest that improvements in the toughness of cement-based composites could be achieved by developing materials in which the decrease in shear stress is less severe.