In situ longitudinal tensile tests of pine wood in an environmental scanning electron microscope

To study wood fracture on its cellular level, small tensile specimens of pine (Pinus sylvestris [L.]) were fractured in situ in tension inside the chamber of an ESEM (Environmental Scanning Electron Microscope). Fractured surfaces of macroscopic tensile test specimens were also studied with an ESEM. The same kind of fracture phenomena were observed in both small and large specimens. The in situ tests proved to be reproducible and the results revealed typical fracture propagation directions and order in softwood under longitudinal tension. The gradual change of material properties of wood in the radial direction was found to strongly influence the fracture process.