Width effect on the modulus of elasticity of hardwood lumber measured by non-destructive evaluation techniques

In the wood construction industry, non-destructive evaluation (NDE) techniques have been successfully used in grading lumber in terms of modulus of elasticity (MOE). However, the research information on the size effect, such as lumber width, on MOE of hardwood lumber measured by NDE techniques is very limited. The aim of this study was to investigate the effect of lumber width on the MOE of hardwood lumber measured by three NDE techniques. The hardwood species tested were yellow birch and sugar maple. Longitudinal stress wave (LSW), free–free beam vibration (FBV), and three-point static bending (TSB) methods were used to determine MOE. The width of a lumber piece was ripped down from 203 mm to 102 mm at an interval of 25 mm. It was found that: (1) The lumber width did not have a statistically significant impact on MOE measured using LSW or FBV, but had an impact on that measured using TSB; (2) Two hardwood species selected had statistically significantly different MOE. The MOE of yellow birch lumber was about 11% higher than that of sugar maple lumber regardless of testing methods and lumber width and (3) The mean of MOE measured using TSB had the highest values, which was about 5% and 10% higher than those measured using LSW and FBV, respectively, regardless of the lumber width and species.