Volume 16, Issue 1, 2007

A REVIEW OF THE PULL-OUT MECHANISM IN THE FRACTURE OF BRITTLE-MATRIX FIBRE-REINFORCED COMPOSITES

Konstantinos G. Dassios

Department of Materials Science, University of Patras, Rio GR-26504, Greece, e-mail: kdassios@upatras.gr

Received 28 July 2006; accepted 7 February 2007

ABSTRACT
The current work addresses the role of damage mechanisms such as interfacial debonding, crack deflection, bridging and sliding during fracture of a brittle-matrix fibre-reinforced composite with respect to their energy dissipation capacity and their impact on the pull-out mechanism. The aim of the paper is to explain why fibre failure is preferably concentrated within the matrix environment to give rise to the pull-out mechanism and not within the crack flanks where fibre stress is maximum. Two approaches, mechanics of materials and fracture mechanics, are invoked to demonstrate that pull-out is triggered and dominated primarily by the fibres’ surface flaw distribution rather than by fibre strength. The origins of pull-out are also explained in terms of statistics and the identified failure pattern of fibres in composites is discussed in view of its implications to experimental practice. The implications of the findings are summarized in a current need for a deeper investigation into the micromechanics of reinforcement in composites, the role of surface flaws and the interface as well as in the competing roles of strength and flaw size.