ABSTRACT:In this study, the change in shear strength on radial and tangential surfaces of Calabrian Pine (Pinus brutia Ten.) wood having different roughness values as the result of sawing with a circular ripsaw, planing and sanding, and bonded with polyurethane (PU) and polyvinyl acetate (PVAc) adhesives at the pressure levels of 3, 6, and 9 kgf/ cm 2 , was studied. Each of the 360 specimens prepared to determine the effect of the variables on bond performance were subjected to shear test in an universal test machine in accordance with the ASTM D 905-98 standards. The values obtained were analyzed statistically and the results were interpreted. The highest shear strength (11.83 N/mm 2 ) for plane of cut was obtained on the tangential surface after sanding and applying PVAc adhesive with a pressing pressure of 9 kgf/cm 2 . The lowest shear strength (6.01 N/mm 2 ) was obtained in the joinings made on the planed surfaces by using PU adhesive and a pressing pressure of 3 kgf/cm 2 .The highest shear strength (9.10 N/mm 2 ) on the radial surface was obtained after sanding and applying PVAc adhesive and pressing with a pressure of 6 kgf/cm 2 . The lowest shear strength (3.76 N/mm 2 ) was obtained in the specimens whose surfaces were sanded and glued with PU adhesive with a pressing pressure of 3 kgf/cm 2 . In general, in the radial surfaces, just like in the tangential surfaces, the specimens bonded with PVAc exhibited a higher shear strength compared with those glued with PU. According to these results, it is definitely necessary to sand the surfaces prior to the bonding process to have a higher shear strength. The bonding process should be made on the tangential surfaces with higher pressures. The PVAc adhesive should be preferred instead of the PU adhesive.

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ABSTRACT:In this study, the change in shear strength on radial and tangential surfaces of Calabrian pine (Pinus brutia Ten.) wood having different roughness values as the result of sawing with a circular ripsaw, planning, and sanding, and bonded with polyurethane (PU) and polyvinyl acetate (PVAc) adhesives at the pressure levels of 3, 6, and 9 kg f/cm 2 were studied. A total of 360 specimens of each, prepared with the objective of being able to determine the effect of the variables on bond performance, were subjected to the shear test in the universal test machine in accordance with the ASTM D 905-98 standard. The values obtained were analyzed statistically and the results were interpreted. The highest shear strength (11.83 N/mm 2 ) for plane of cut was obtained on the tangential surface after sanding and applying PVAc adhesive with a pressing pressure of 9 kg f/cm 2 . The lowest shear strength (6.01 N/mm 2 ) was obtained in the joinings made on the planed surfaces by using PU adhesive and a pressing pressure of 3 kg f/cm 2 . The highest shear strength (9.10 N/mm 2 ) on the radial surface was obtained after sanding and applying PVAc adhesive and pressing with a pressure of 6 kg f/cm 2 . The lowest shear strength (3.76 N/mm 2 ) was obtained in the specimens whose surfaces were sanded and by using PU adhesive and with a pressing pressure of 3 kg f/cm 2 . In general, in the radial surfaces, just like in the tangential surfaces, the specimens bonded with PVAc produced a higher shear strength compared to those glued with PU. According to these results, it is definitely necessary to sand the surfaces prior to the bonding process to have a higher shear strength. The bonding process should be made on the tangential surfaces with higher pressures. The PVAc adhesive should be preferred instead of the PU adhesive.

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