Influence of a matrix crack on stress transfer to an α-alumina fibre in epoxy resin using FEA and photoelasticity

Elasto-plastic finite element analysis was used to investigate the influence of a transverse matrix crack on the matrix stress transfer to an isolated alumina fibre in epoxy resin. With an increase in transverse crack length perpendicular to the fibre the stress transfer length of the fibre (STL) increased, thereby reducing its reinforcing efficiency. The maximum shear stress at the fibre/matrix interface was found to be displaced away from the fibre-break. Phase-stepping automated photoelasticity was used to quantify the stress field surrounding the broken fibre in the presence of a transverse matrix crack which had propagated into the epoxy resin matrix. The interfacial shear stress was calculated from these stress fields and compared with the finite element analysis. A reasonable agreement was obtained. The maxima in the shear stress plot observed in the FEA calculations were also observed in the photoelasticity results.