PEER-REVIEWED ARTICLE bioresources.com Mirbolouk & Roohnia (2015). “MDF longitudinal vibration,” BioResources 10(1), 613-621. 613 Evaluation of Dynamic Modulus of Elasticity of Medium Density Fiberboard Panel from Longitudinal Vibration Tests on Specimens Parinaz Mirbolouk, and Mehran Roohnia* It is preferred to perform conformity assessment of wood-based panels on the whole panel without cutting it down to smaller pieces. The modulus of elasticity, a mechanical property of wood, was determined by longitudinal vibration testing with the full-size panel, and the results were compared with results of tests of prismatic beams. The Brancheriau’s correction coefficient was used to compensate for errors from cross-sectional dimension variations and errors from Poisson’s ratio. Longitudinal excitation of the panels along the length was shown to be successful in evaluating the modulus of elasticity. However, strong correlations obtained from plate and beam comparisons along the width of the panels are promising. Keywords: Composite; Longitudinal vibration; MDF; NDT; Plate; Wood Contact information: Department of Wood and Paper Science and Technology, College of Agriculture and Natural Resources, Karaj Branch, Islamic Azad University, Karaj P. O. Box 31487-313, Iran; * Corresponding author: mehran.roohnia@kiau.ac.ir INTRODUCTION To be judged successful, a nondestructive test (NDT) of wood must provide suitable information without causing any failure or change in the nature of the specimen. Since a test specimen is typically cut from a larger specimen, the first step of destruction is manually enforced during fabrication of the valuable merchandise. In industrial practice, when such destruction is small, the method is sometimes falsely considered as a nondestructive evaluation. Resisto-graph drillings for standing tree assessment (Costello and Quarles 1999) and screw withdrawal tests to estimate the shear strength of wood (Divos et al. 1998) might be considered as two outstanding examples. Despite these kinds of informalities, researchers are working to develop NDT techniques to be absolutely nondestructive as implied by their name. For medium density fiberboard (MDF), the modulus of elasticity is the most important mechanical parameter, and it is highly correlated with another key attribute, the modulus of rupture. These parameters must be evaluated by accredited import/export inspection bodies to judge whether or not wood specimens meet the applicable standards. Nowadays, when following standard procedures, it is common to use a static bending method that results in failure. If forced or free vibration of a free bar is conducted as an alternative, there is destruction involving the initial cutting down of the whole MDF board into smaller prismatic beams. The present research aims to find a solution to enable nondestructive evaluation of the modulus of elasticity in whole full-sized panels of MDF.