 Fibre-matrix load transfer

Fibre-matrix load transfer describes how interfacial shear stress transfers axial force between a reinforcing fibre and its surrounding composite matrix. For a cylindrical fibre of diameter $d$, axial force balance gives $d{\sigma }_f/dx=4\tau /d$ when $\tau$ is the appropriately signed interfacial shear stress.

The fibre stress is therefore small near a free end and builds over a transfer length. Short fibres may never reach their tensile strength before the interface slips or the matrix yields. The critical fibre length quantifies this competition in a simplified constant-shear model.