Abstract
The surface roughness constitutes one of the most critical properties of wood and wood veneers for their extended utilization, affecting the bonding ability of the veneers with one another in the manufacturing of wood composites, the finishing, coating and preservation processes, and the appearance and texture of the material surface. In this research work, logs of five significant European hardwood species (oak, chestnut, ash, poplar, cherry) of Balkan origin were sliced into decorative veneers. Their surface roughness was examined by applying a stylus tracing method, on typical wood structure areas of each wood species, as well as around the areas of wood defects (knots, decay, annual rings irregularities, etc.), to compare them and assess the impact of the defects on the surface quality of veneers. The chestnut veneers presented the smoothest surfaces, while ash veneers, despite the higher density, recorded the highest roughness. In most of the cases, the roughness was found to be significantly lower around the defects, compared to the typical structure surfaces, probably due to lower porosity, higher density and the presence of tensile wood. The results reveal that the presence of defects does not affect the roughness of the veneers and increases neither the processing requirements of the veneer sheets before finishing, nor the respective production cost of veneers and the veneer-based wood panels. The high utilization prospects of the examined wood species in veneer production, even those bearing various defects, is highlighted.
Highlights
The surface of each material or final product consists of a miniature of peaks and valleys, the size and distribution of which determine the surface properties of the material, such as roughness, texture, etc
The purpose of this study is to examine the surface roughness parameters values of sliced veneers made of five different species significant for veneer production European hardwood species, are investigated, for the first time according to the literature, in terms of how their roughness level is influenced by the presence of various structural defects in the mass and surface of veneers, such as knots, irregularities of annual rings structure, decay, discoloration etc., compared to typical structure surfaces of each wood species’ veneers
The cutting machine used for the slicing of veneers was of horizontal operation, since this is suitable for the veneer slicing of hardwood species and they were all cut into plain cut veneers
Summary
The surface of each material or final product consists of a miniature of peaks and valleys, the size and distribution of which determine the surface properties of the material, such as roughness, texture, etc. Roughness greatly affects its aesthetics and the structures in which it participates, and should be in line with the criteria and requirements of consumers in terms of quality. As regards wood veneer sheets, rough surfaces of veneers negatively affect the appearance of the finished products, and affect manufacturing processes such as coatings and adhesion appliance, and adhesion strength, since they reduce the contact between them, resulting, according to the literature, in weak interactions between glue and wood and, low-strength properties of laminated veneer lumber, plywood and several other wood-based composites [1,2,3].
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