Characterisation and modification of the heat affected zone during laser material processing of wood and wood composites

The heat affected zones (HAZ) at laser cut and laser joint wooden material surfaces were characterised measuring the temperature profile of the process within the cut kerf of particleboard and plywood, as well as the HAZ of the CO2 laser cut and Nd:YAG laser joint pine (Pinus sylvestris L.) surface using microscopy, UV microspectrophotometry and pyrolysis-GC/MS. The width of the HAZ can be selectively modified within the range of 14-70 mu m. The HAZ systematically depends on the material and process parameters, such as earlywood or latewood fibre, cut direction and laser energy per section. The thermal induced changes in wood composition were analysed for lignins and carbohydrates. The chemical and structural modifications seem to be most intense at the laser treated surface and decreases to levelling off at 35-40 mu m distance from the surface.