Theoretical model of fiber debonding and pull-out in unidirectional hybrid-fiber-reinforced brittle-matrix composites

A theoretical model is developed to study the fiber debonding and pull-out in hybrid-fiber-reinforced brittle-matrix composites. By adopting the shear-lag model which includes the matrix shear deformation in the bonding region and friction in the debonding region, the relationship between the pull-out length and the debonding length of fiber is obtained by treating the interface debonding as a particular crack propagation problem along the interface. The interface debonding criterion for the hybrid-fiber-reinforced composites is obtained by applying the energy release rate relation in an interface debonding process. The analysis is applied to hybrid carbon/glass fiber-reinforced epoxy composites, and the theoretical results have a reasonable agreement with the experimental data. The hybrid effect is studied and the effect of material parameters is discussed.