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Understanding the Function of Rays and Wood Density on Transverse Fracture Behaviour of Green Wood in Three Species



Author(s)

Seray Ozden and Anthony Roland Ennos

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DOI:10.17265/2161-6264/2014.09.006

In recent years, there has been an increasing interest in wood properties, because wood is a commonly used and advanced building material. In this paper, the effect of anatomical characters on the transverse fracture properties of green wood was investigated. The specific fracture energy (G_f J/m²) of ash (Fraxinus excelsior), cherry (Prunus avium) and birch (Betula pendula) was evaluated using double edge notched tensile tests. The tests were performed on both earlywood (EW) and latewood (LW) zones in both the radial-tangential (RT) and the tangential-radial (TR) crack propagation systems. Wood anatomy and the failure patterns of each species were also investigated using environmental scanning electron microscopy (ESEM) and light microscopy (LMC). The results showed that the G_f of RT fracture systems was around 1.5 times greater than in the TR one, whereas there were no significant differences between EW and LW zones. ESEM micrographs showed that the RT fracture system had a rougher fracture surface, while the TR had a nearly smooth and flat fracture surface. In particular, the wood of F. excelsior was the toughest, because of its greater percentage of rays and homogenous distribution of ray cells, while P. avium and B. pendula showed a lower G_f due to their smaller percentage of rays with a distinctive arrangement of ray cells.

Green wood, fracture energy, rays, transverse failure.