IN-SITU FRACTURING OF WOOD IN THE SCANNING ELECTRON-MICROSCOPE

Studying fracture initiation and propagation in wood at a microscopica l level should provide much information about fracture mechanics and c ell wall structure. To this end, a method was developed to carry out f racturing of wood in a scanning electron microscope. A bending and a t ension 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.). Cra ck initiation and propagation were recognized and recorded in most sam ples. Although Scanning Electron Microscopy proved to be very useful, it also poses some difficulties. The electron beam can strongly influe nce the fracture behaviour and morphology of wood. However, electron b eam damage-induced fractures in wood have very characteristic features and, therefore, can be distinguished from natural fractures. If certa in precautionary measures are observed, electron beam damage can be av oided.