Effect of Surface Roughness on the Shear and Tensile Strength of Hardwood Adhesive Joints: A Linear Elastic Model

Abstract

This study analyzed the bond line strength of Eucalyptus sp. specimens submitted to shear and perpendicular to grain tensile forces, depending on the wood quality machined surface. The woods plans were glued with two different polyvinyl acetate adhesives. The bonding surfaces were milling with three different feed speeds; 6.0, 11.0 and 15.0 m/min, corresponding to the feed per tooth of the cutting tool; 0.86, 1.57 and 2.14 mm, respectively. The specimen types corresponded to the standards according to ABNT NBR 7190/1997. The cutting plane considered only the geometry of milling due to the bond line joint strength. To explain the experimental results, was proposed a linear elastic model to machined wood and bond line. For the two adhesives used, the experimental results suggest that the greatest perpendicular to grain tensile strength and shear strength were obtained to bond surface machined with the intermediate feed speed namely 11 m/min, for others two feed speeds and in the shear strength case, was not observed a distinction between them, in the perpendicular to grain tensile strength, the feed speed 6.0 m/min presented a higher strength than the machined surface with 15.0 m/min. The model reproduces the behavior of the experimentally results obtained for the two tests, and so it can be readily applied as a tool for evaluate the machining feed speed and the bond line joint strength.