Moire interferometry analysis of fiber debonding

Progressive fiber debonding in steel fiber/cementitious matrix composites h as been studied using a single fiber pullout test that permits simultaneous measurements of the load versus crack opening displacement relationship an d Moire interferometry fringe patterns. Analysis of Moire interferometry pa tterns allows the fiber axial and interfacial shear stresses to be calculat ed 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 mum of fiber slip and a crack opening displacement of 22 mum. These results suggest that improvem ents in the toughness of cement-based composites could he achieved by devel oping materials in which the decrease in shear stress is less severe.