Stress concentration in a circular hole in composite plate

A non-contact measurement method, namely electronic speckle pattern interferometer (ESPI), was used to investigate the tensile strain field of a composites plate in the presence of stress concentrations caused by a geometrical defect consisting of circular hole. ESPI uses the principle of 3D speckle interferometry to measure the deformation and contour of the measuring field with submicrometer accuracy. The ESPI technique clearly revealed the strain concentrations near the singularity. The experimental results are compared with the predictions of a theoretical model previously developed by Lekhnitskii's and a finite element study. (c) 2004 Elsevier Ltd. All rights reserved.