Grain angle determination of silver birch by laser light scattering and tensile fracturing

Abstract

Reliable non-destructive methods for grain angle determination are essential for the evaluation of mechanical properties of timber. In the present study, the detection of grain angle by means of laser light scattering patterns is investigated on small-scale specimens and timber boards of silver birch, along with the relationship to fracture angle and tensile strength. Results on small-scale specimens indicate applicability of laser scattering method, as the detected grain angles and the fracture angles show a strong correlation, $$r = 0.94$$ r = 0.94 . Three-dimensional grain angles, derived from surface grain angles, show a well defined relationship to strength, which can be described with wood-based failure criteria from literature. Furthermore, the paper presents new findings regarding the detection of flame wood through laser scattering. It was shown that small-scale specimens with flame wood tend to have higher grain angles, higher density, and lower strength, relative to specimens without. Nevertheless, for timber boards, the influence of flame wood on the strength was insignificant.

Modelling the Effect of Three-Dimensional Grain Angle on the Tension Strength of Birch Wood

“…A total of 119 specimens were investigated. The specimens were sawn from the ends of timber boards with a wide range of grain angles [5]. The specimens are (dogbone) shaped with a reduced gauge region of 200 mm in length (Figure 1).…”

“…Density was measured from a section of the gauge region after testing and the influence of density on the tension strength of this sample was investigated in a previous study [5]. Wherein, it was found that density had no unambiguous relationship with the tension strength.…”