Dynamic and static comparison of Dovetail , Tongue and Groove in Firs

The aim of this study is to evaluate the dynamic and static of elastic properties of Fir wood joints. For this purpose conventional joints in woos industry including dovetail, tongue and groove beech wood (Abies alba.) joints with polyvinyl acetate (PVA) and cyanoacrylate (CA) adhesives were used. Dimensions of research samples were determined 24×50×360 (mm) according to international standard (ISO No.3129), and the results indicate that the effects of joint type, adhesive type, joint size, and also retrospective joint size became meaningful at 5% level in dynamic and static tests. As the length of groove and height of dovetail and length of dowel increased in the joints, dynamic and static elasticity modules increased, and in terms of changes in elasticity modules of the research. Elasticity module for dovetail joint, as a result of the shape, having a homogenous joint texture, and also lack of extended adhesive line in the joint, is closer to un jointed samples (control group). Also cyanoacrylate adhesive improved elasticity features of samples compared to polyvinyl acetate adhesive as a result of higher tension resistance and faster coagulation. The results of the Student's t-test indicate that there exists a not significant difference between the mean of dynamic and the mean of static modulus of elasticity, not significance at 5% level and The Pearson correlation test indicate that the dynamic and static modulus of elasticity of the samples are significant at 5% level and are of positive correlation(+.0958) .With regard to the correlation of the results of dynamic and static tests, methods for non-destructive dynamic investigation may be regarded as appropriate alternatives to destructive static tests, in order to assess and classify woods.