Effect of size on the dynamic and static bending of green wood samples of European beech

Abstract

In recent years, there has been growing interest in assessing the properties and quality of green hardwood by non-destructive testing (NDT). The frequency resonance technique (FRT) has proven to be an effective NDT method in the assessment of green wood. The properties of green wood with complex structures are often estimated based on the mechanical properties of standard samples. This raises two questions: (1) What effect does size have on the obtained mechanical properties of wood during bending? and (2) Is it possible to describe or predict this effect by using FRT on a different size and structure? In this study we monitored differences in the dynamic modulus of elasticity in bending (MOED), the flexural modulus of elasticity (MOE) and the flexural modulus of rupture (MOR) in samples of different sizes and shapes. Four groups of bending samples with a square cross-section (7 mm×7 mm×100 mm, 20 mm×20 mm×300 mm, 40 mm×40 mm×600 mm and 60 mm×60 mm×900 mm) and two groups of branch samples with near-circular cross-section (±80 mm×880 mm; diameter ±100 mm×1120 mm) of European beech wood were tested. The results show that no relationship between MOED, MOE and MOR and the size of samples was conclusively confirmed. A strong relationship between MOED and MOE or MOR for all square cross-sections was shown by the results.