Determination of the Static Bending Properties of Green Beech and Oak Wood by the Frequency Resonance Technique

This article discusses the non-destructive evaluation of the mechanical properties of green wood. To estimate the dynamic flexural modulus of elasticity (MOED), a non-destructive test (NDT) method—the frequency resonance technique (FRT)—was used. A three-point bending test was carried out to determine the static bending properties as the bending modulus of elasticity (MOE), the modulus of rupture (MOR), and bending toughness (Aw). This article presents the results of a study comparing the correlations between the dynamic and static bending parameters of beech (Fagus sylvatica L.) and oak (Quercus robur L.) wood, which was further divided into heartwood and sapwood. These species were chosen as the most widespread representatives of diffuse-porous and ring-porous hardwoods. This study found statistically significant differences in most mechanical parameters between the two species, except for MOR. Among the investigated parameters, beech had higher values than oak (by 22.1% for MOED, 9.5% for MOE, and 12.1% for Aw). Furthermore, relevant correlations (R > |0.7|) were established between MOED and between some of the static flexural parameters. These correlations were stronger for beech, which due to its more homogeneous structure showed less data variability than the ring-porous oak.