ON THE PULL-OUT OF FIBERS WITH A BRANCHED STRUCTURE AND THE INFERENCEOF STRENGTH AND FRACTURE-TOUGHNESS OF COMPOSITES

In an experimental investigation of the pull-out of synthetic fibres w ith branched structure, it was generally observed that the force and e nergy of fibre pull-out are greater than those for plain fibres, and i ncrease with the branching angle. An approximate theory of pull-out of fibres with branched structure from a matrix is developed with the ai m of quantifying the effect of the branched structure of the fibre. Th is theory agrees well with the experimental results by adjusting the s nubbing friction coefficient between fibre and matrix and neglecting t he bending of the fibre at the fibre branching point. The strength and fracture toughness of a composite reinforced by this type of fibre ar e inferred to be greater than those of composites reinforced with plai n fibres.