European beech log and lumber grading in wet and dry conditions using longitudinal vibration

Abstract

Abstract In Central Europe, European beech (Fagus sylvatica L.) is the most frequently occurring hardwood species. An efficient grading method has the potential to promote its utilisation as construction material. Wood density, eigenfrequency and length were measured in 99 European beech logs for calculating the dynamic modulus of elasticity (MOEdyn ) obtained by longitudinal vibration (resonance). In addition, the log taper was measured. Of those logs, 867 boards were cut using a bandsaw. The MOEdyn in green condition was determined on 505 of the boards and the MOEdyn in dry conditions was determined on all of them. The r2 value between the MOEdyn of a log and the mean of MOEdyn of its boards was 0.72 in the wet condition. The MOEdyn,12% of boards significantly increased by 88 N mm−2 for each centimetre away from the pith. The negative effect of log taper on MOEdyn of boards was barely significant (P-value = 0.050). The MOEdyn,12% was highly dependent on the MOEdyn,wet (r2 = 0.83) and was 17% higher than the MOEdyn,wet . The mechanical properties of European beech timber exceed those of European softwood species. However, the relationships regarding MOEdyn between different grading levels in the processing chain appear to be similar to those of softwoods.