In-situ fracturing of wood in the scanning electron microscope

Studying fracture initiation and propagation in wood at a microscopical level should provide much information about fracture mechanics and cell wall structure. To this end, a method was developed to carry out fracturing of wood in a scanning electron microscope. A bending and a tension module were built to fit the chamber of a SEM. Both devices are designed to observe tension failure. Load was implemented parallel to the grain of wood samples, Norway Spruce (Picea abies L. Karst.). Crack initiation and propagation were recognized and recorded in most samples. Although Scanning Electron Microscopy proved to be very useful, it also poses some difficulties. The electron beam can strongly influence the fracture behaviour and morphology of wood. However, electron beam damage-induced fractures in wood have very characteristic features and, therefore, can be distinguished from natural fractures. If certain precautionary measures are observed, electron beam damage can be avoided.