Variation of impact bending in the wood of Pinus sylvestris L. in relation to its position in the tree

Abstract

The response of the wood of Pinus sylvestris L. to impact bending using the Charpy method was studied in 2940 defect-free, oriented test pieces from the central board of 10 trees felled during scheduled cutting, with the values obtained being related to the position of the test piece in the tree, both from the pith to the outside and in terms of its height in the tree. For this purpose the absorbed energy was obtained by using an instrumented drop-weight impact tester. The tests were carried out in stable hygrothermic conditions of 65±5 percent and 20±2 °C, and the wood was conditioned under the same conditions before testing. The characterisation was carried out on test pieces with a cross section of 20 mm by 20 mm and a length of 150 mm. The results obtained show that impact bending decreases the closer the test piece is to the pith and the higher it is in the tree, with the decrease being greater horizontally than vertically. In addition, it was shown that there is a significant relation between the number of rings and the impact response of the wood. © Forest Products Society 2008.