Comparison of two optical methods for contactless, full field and highly sensitive in-plane deformation measurements using the example of plywood

In the present paper, the suitability of Electronic Speckle Pattern Interferometry (ESPI) and Digital Image Correlation (DIC) for the measurement of two-dimensional strain distribution on mechanically stressed wood specimens is evaluated. Particular attention is dedicated to the basics of the individual techniques in order to discuss potential advantages and disadvantages. The results of a model experiment with plywood show that the results delivered by both methods are very similar and of high quality. ESPI provides reasonably fast experimental set-up and data acquisition, and fast, straightforward post-processing. Compared to ESPI, DIC is a more versatile method demanding skilled sample preparation, and post-processing may be time consuming.