Mechanism of stress transfer in a single wood fibre-LDPE composite by means of electronic laser speckle interferometry

The distribution of strain in a single wood fibre-reinforced-low density polyethylene (LDPE) composite was measured by means of electronic laser speckle interferometry (ESPI). Finite element analysis and analytical analysis of strain distribution in the model composite was performed for validation and confirmed the experimental results. Low strain in the fibre and a concentration of high axial strain in the matrix region close to both fibre ends was measured. The regions of high strain next to the fibre ends indicate a significant transfer of stress from the matrix to the fibre via fibre ends. The distribution of shear strains at the interface along the fibre length measured by ESPI corresponds well to classical shear-lag theory. It is concluded that ESPI is a powerful tool for the unravelling of composite micromechanics.