Moisture-dependent elastic and strength anisotropy of European beech wood in tension

Abstract

While the general mechanical behaviour of wood is known, its moisture-dependent elastic and strength anisotropy remains little studied. Given the anisotropic and hygroscopic nature of wood, a characterisation of wood mechanical behaviour will require knowledge of its moisture-dependent properties in relation to the three principal axes of anisotropy. The present study examines the influence of the moisture content (MC) on the elastic and strength anisotropy of beech wood (Fagus sylvatica L.). Selected elastic and strength parameters, including the anisotropic Young's moduli, Poisson's ratios, yield and ultimate stress values and the fracture toughness in the TR, TL, RT and RL directions, are determined in uniaxial tension and compact tension tests at different moisture conditions. A distinct moisture dependency is shown for the elastic and strength behaviour of beech wood. With the exception of some Poisson's ratios, all investigated elastic and strength parameters are shown to decrease with increasing MC. The two-and three-dimensional representation of the compliance matrix, and the two-dimensional visualisation of a yield surface, provides a valuable overview on the moisture-dependent elastic and strength anisotropy of beech wood.

Anisotropic elastic properties of common ash (Fraxinus excelsior L.)

“…The maximum values of compliance are reached at an angle of about 45° because of a comparable low shear modulus in the RT plane. However, yew wood reveals a different behavior with a much lower degree of anisotropy (Garab et al 2010), comparable to theoretically determined values by Grimsel (1999), Hering et al (2012), and Ozyhar et al (2012), for hardwoods like beech. The calculations were conducted according to an approach described in Bodig and Jayne (1993), on the basis of works by Voigt (1928), and Hörig (1933).…”

“…Comparing the shape (Figure 4a) to displays of several different softwood and hardwood species by Grimsel (1999), Lang et al (2002), Keunecke et al (2008), Hering et al (2012), and Ozyhar et al (2012), only a small degree of anisotropy was visible in the case of ash; very comparable to the deformation bodies of beech or mahogany with the highest deformability in the T direction. Under torsion loading (Figure 4b), ash shows nearly isotropic behavior, also very comparable to the deformation bodies of the hardwoods like beech or mahogany.…”

“…Selected parameters of ash and other hardwoods have been published by Baumann (1922), Stamer (1935), Kollmann (1941Kollmann ( , 1951, Kühne (1951), Leclerco (1975), Bodig and Jayne (1993), Sliker and Yu (1993), Szalai (1994), Wagenführ (1996), Pozgaj et al (1997), Sell (1997), DIN 68364 (2003, Bonoli et al (2005), amongst others. A few authors also presented results obtained for the traverse directions of individual softwood and hardwood species, such as Hörig (1933), Wommelsdorf (1966), Neuhaus (1983), Keunecke et al (2008), Hering et al (2012), and Ozyhar et al (2012). However, especially in the case of hardwoods, complete data sets for the three main anatomical directions rarely exist that are sufficient for static calculations and modeling in wood construction, and for calculations on multilayered boards, parquet, or musical instruments with the finite element (FE) method.…”

Lastnosti bukovine in njena raba

“…Razlike v natezni in tlačni trdnosti so manjše kot pri iglavcih (Gustafsson, 2010), posledica pa je visoka upogibna trdnost, ki je merilo za orientacijsko oceno mehanskih lastnosti lesa (Teranishi et al, 2008). Homogena zgradba bukovine se odraža tudi na manjši »mehanski« anizotropiji, ki še zlasti omogoča uporabo bukovine za luščen furnir, za krivljenje, struženje in prispeva k stabilnosti tlačno obremenjenih vitkih konstrukcijskih elementov Ozyhar et al, 2012).…”

Influência do teor de umidade na propriedade de tenacidade de espécies florestais

“…Devido à natureza anisotrópica e higroscópica da madeira, a caracterização de seu comportamento mecânico exige o conhecimento de suas propriedades dependentes de umidade, uma vez que a madeira, em muitas aplicações, é exposta a diferentes condições climáticas (Ozyhar et al, 2012 Beltrame et al (2012) pesquisaram a influência do teor de umidade (12% e saturado) na resistência ao impacto da madeira de nogueira-pecã (Carya illinoinensis), procedentes de duas regiões fisiográficas do Estado do Rio Grande do Sul. Os corpos de prova foram preparados e testados quanto aos sentidos da resistência, radial e tangencial, e às posições de retirada, próxima à medula e próxima à casca.…”