Analysis of Fiber Debonding and Pullout in Composites

Abstract

The debonding and pull‐out behaviors of fibers in composites are examined. The debonding and pull‐out processes are analyzed separately and then combined to model the global behavior of fiber/matrix interface. The debonding of a single fiber is analyzed based on fracture mechanics. In this approach, the debonded region is treated as an interfacial crack, and the Griffith energy criterion is assumed to govern the extension of this crack. Fracture parameters that are material properties of the interface are determined for the debonding process. The pull‐out process is considered to be dominated by frictional shear stress acting over the debonded interface, both during debonding and after the delamination is complete. The frictional contribution to total load resistance is estimated from previous experimental results. The proposed approach is applicable to any elastic fiber and matrix system, but only the results of steel fibers in a cementitious matrix are reported. Finally, the fracture parameters are used to predict the behavior of steel fibers of varying dimensions. The theoretical predictions are in good agreement with experimental results reported by other investigators.