Comparison of Non-Destructive Methods Based on Natural Frequency for Determining the Modulus of Elasticity of Cupressus lusitanica and Populus x canadensis

A non-destructive method for measurement of the modulus of elasticity (MOE) was compared with the static method on beams of Cupressus lusitanica and Populus x canadensis. The dynamic method is based on the principle of the resonance frequency, using longitudinal vibrations (Timber Grader MTG, accelerometer) and the static method for measurement of the flexural modulus of elasticity is according to EN 408 (2012). The differences between the ascertained dynamic and static MOE values were 1.1% to 2.4% for the Populus x canadensis sample and 12.7% to 15.5% for the Cupressus lusitanica sample. Furthermore, the correlation dependence of the applied methods was determined and the regression equations are shown. Experimental measurement showed the effect of the knot clusters, which appeared primarily in Cupressus lusitanica samples and considerably impacted the resultant values.