Wood lab 2003
Anisotropy of Wood
Wood beams are always cut so that the cellulose fibers run along the length of the beam (that is, they are cut with the grain). In this video, we compare the strength of bars of wood cut with or across the grain. The latter are brittle, failing suddenly after a small deflection. The former undergo a huge deflection before the strength is reduced in half, and most of the deflection recovers when the load is removed. This anisotropy (direction-dependence) of the properties of the wood results from the orientation of the cellulose polymers that make up the walls of the cells in the wood.