An analysis of interfacial debonding in beaded fiber composites

Intermittent beading is a novel design that holds great potential for simultaneous improvement of strength and toughness of composites. Despite the progress in fabrication of beaded fiber composites, the mechanisms of fracture in such composites are largely unknown. In this study, calculations are carried out for interfacial debonding in a beaded fiber composite subjected to tensile loading. The post-yield strain softening followed by strain hardening of polymer matrix, and debonding of the fiber-bead, bead-matrix and fiber-matrix interfaces are accounted for in the numerical analyses. It is found that interfacial debonding can activate plastic deformation in the bead and polymer matrix, contributing to toughening of the beaded fiber composite. We have identified that the bead-matrix interfacial debonding is the major mechanism controlling plastic deformation in the matrix. The low cohesive strength of the bead-matrix interface plays a role in suppressing development of shear bands in the polymer matrix, enhancing plastic dissipation of the composite. The high toughness of the bead-matrix interface enables large plastic zone in the matrix, promoting plastic dissipation. For the fiber-bead interface, there is an increase in plastic dissipation of the composite with decreasing cohesive strength, while high interface toughness can amplify plastic dissipation. In addition, we reveal that weak fiber-matrix interface is capable of spreading plastic deformation in the matrix, increasing plastic dissipation of the composite. The findings of this study can shed new light on the fracture mechanisms of beaded fiber composites.