Wood stiffness by x-ray diffractometry

As a first approximation, wood can be modeled as a two-phase composite material consisting of load-bearing, highly crystalline S-2 cellulose microfibrils and relatively non-load-bearing "matrix" material including lignin, hemicelluloses, amorphous cellulose, and crystalline cellulose in microfibrils oriented well away from the fiber axis (in the S-1 and S-3 wall layers). A new rapid X-ray diffractometric method, based on this concept, is proposed for estimating the longitudinal stiffness of wood in increment cores by X-ray diffractometry. The method does not involve the estimation of microfibril angle, although this property is indirectly taken into account. X-ray diffractometry allows a crude separation of these two phases to yield a simple wood stiffness model that appears to apply to a wide range of species without further calibration.