Effects of cell anatomy on the plastic and elastic behaviour of different wood species loaded perpendicular to grain

Abstract

In radial compression, the shape of the stress-deformation curve varies for different wood species, particularly at the transition from elastic to plastic deformation and along the stress plateau. Due to differences in anatomy and cell wall microstructure, different responses to perpendicular loads were observed in spruce (ductile plastic deformation), oak (brittle failure), and beech (elastomeric yielding). Beginning plastic deformation was examined by SEM after the application of different compression levels and by dynamic observations during the loading process of small samples under a light microscope. It was demonstrated that radial compression of spruce is limited by the critical Euler buckling load of only a few cells closely behind the ring border. The compression behaviour of oak is determined by the buckling of the earlywood vessels and vasicentric tissue, whereas beech is characterised by the densification of the vessels at high plastic deformations.