Erol Burdurlu

The effect on shear strength of different surfacing techniques in Oriental beech (Fagus orientalis Lipsky) and Scotch pine (Pinus sylvestris L.) bonded joints

The selection of the most appropriate surfacing technique is influential in the success of bonding, painting and varnishing processes. The objective of the study was to determine which surfacing technique was the most appropriate when applied as the final process in the production of structural wood members, which were subjected to shearing. The study also includes the effect on shear strength of the variables, such as type of wood, plane of cut, type of adhesive and pressing pressure, as they are directly related to the main objective of the study. In view of this objective, the changes in shear strength on radial and tangential cut surfaces of Oriental beech (Fagus orientalis Lipsky) and Scotch pine (Pinus sylvestris L.) woods having different roughness values as a result of sawing with a circular ripsaw, planing and sanding, and bonded with polyurethane (PU) and poly(vinyl acetate) (PVAc) adhesives at 3, 6 and 9 MPa pressure, were studied. The 936 specimens prepared with the objective of determining the effects of variables on bond performance were subjected to a shear test in a universal test equipment in accordance with the ASTM D 905-98 standard. The highest shear strength (13.85 N/mm2) was obtained for the Oriental beech specimens cut from their tangential surfaces with a circular ripsaw, which were glued with PVAc adhesive by applying a pressure of 9 MPa. The lowest value (4.22 N/mm2) was obtained in the specimens planed from their tangential surfaces, which were glued with PU adhesive by applying a pressure of 3 MPa. The specimens obtained from Oriental beech wood showed a higher shear strength compared to the specimens obtained from Scotch pine. In general, in both species of wood, the specimens glued with PVAc adhesive, both on the tangential surfaces and on the radial surfaces, produced higher shear strengths compared to the specimens glued with PU adhesive.

Determination of Screw Holding Strength of Some Wood Materials

Bu calismada, Dogu kayini (Fagus orientalis Lipsky), saricam (Pinus sylvestris L.), mese (Quercus borealis Lipsky), kestane (Castanea sativa) ve ceviz (Junglans regia) malzemelerinin radyal, teget ve boyuna yonde vida tutma mukavemetleri arastirilmistir. Bu deneylerde bes tur agac, uc farkli vida cekme yonu, iki tip sabitleme ve her degiskenden on tekrar olacak sekilde toplam 300 adet numune hazirlanmis ve statik yuk altinda dogrusal vida cekme deneyine tabi tutulmustur. Deneyler sonucunda, en yuksek vida tutma mukavemeti ceviz, en dusuk ise kestane odunlari uzerinde elde edilmistir. Agac malzemelerin ozgul agirligi arttikca, vida tutma direnci de artmaktadir. Genel olarak radyal yonde cekme, teget ve boyuna yonde cekmeye kiyasla, teget yonde cekme de boyuna yonde cekmeye kiyasla daha yuksek vida tutma mukavemeti gostermektedir