Electronic speckle pattern interferometry for mechanical testing of thin films

The design, performance and principles of computerised control of an optical micro-electromechanical device combining microtensile device and electronic speckle pattern interferometry (ESPI) to test both elastic and plastic properties of thin metallic, dielectric as well as multilayered freestanding films are presented. A piezo-actuated microtensile Set LIP is synchronised with an ESPI to measure film elongation tip to 70 mum length with an accuracy of nearly 50 nm. No patterning or marking of the specimen surface is needed when using the ESPI and displacements can be measured at various points of the films. Tensile force is directly measured using a miniature load cell. Tensile tests of 10 mum aluminium and 50 mum polymer (Kapton(R)) foils have been performed. The Young's moduli are calculated for both materials from the stress-strain Curves. (C) 2003 Elsevier Ltd. All rights reserved.