Microstructure and fracture mechanical response of wood

Investigations on the fracture properties of wood in relation to its microstructure are reported. The inhomogeneous and hierarchical structure of wood is addressed. Wood species, the influence of orientation, the role of structural features, like rays are considered and discussed. Likewise the mode of loading, which determines the mode of fracturing, and the influence of humidity have been studied by using new fracture mechanical techniques and ways of evaluation. The specific fracture energy has been determined under crack opening conditions. In-situ loading in an environmental scanning electron microscope (ESEM), which allows observation in moistured condition, has been performed in order to investigate the mechanisms of fracturing of wood on a sub-microscopic scale. In the nanometer range, especially the influence of the microfibril angle on deformation and fracture behaviour has been studied.