Thermo-mechanical behaviour of wood and wood products

The dynamic mechanical behaviour of solid wood, fibreboard, and wood laminates has been examined in the temperature range –100 to +150° C. Two events are apparent in the response of the solid wood, a low-temperature (–50° C) transition which is interpreted as being associated with the onset of movement of bound water, and a higher temperature (40 to 120° C) thermal softening process. With fibreboard, the relationship between the shear storage modulus and density is shown to be described by a simple packing efficiency factor applicable over a wide range of temperature. The behaviour of the laminates is strongly dependent upon the orientation of the outer ply. A model is proposed which analyses the response of the laminate in terms of its constituent plies and allows calculation of numerical values of the component shear storage moduli. With both the fibreboard and the laminates the binder, urea-formaldehyde resin, is shown to have a significant influence on the absolute values of tan observed.