The influence of moisture content on the mode I fracture behaviour of sprucewood

The moisture content is known to influence the properties of wood. While mechanical parameters like stiffness and strength decrease with increasing moisture content, investigations on the influence on fracture properties have been concentrated on linear elastic fracture mechanics. In this paper, the wedge splitting method is used to investigate also the non-linear fracture behaviour of sprucewood at different moisture contents. Complete load-displacement curves at four different moisture levels are evaluated. While the initial slope and the maximum stress state are decreasing with increasing moisture content the specific fracture energy is increasing. It is shown that this behaviour can be attributed to an increase in ductility which increases both the dissipated energy during crack initiation and the one in the crack propagation phase.