Investigation on Bending and Compression Strength of Paulownia fortunie Wood Grown in Gorgan Region

Bending and compression strength of Paulownia fortunie wood grown in educational and research forest located at Shastkalate, Gorgan were studied. Paulownia trees were selected among five years old plantation. Sampling spot was conducted following standard procedure. Trees were cut into logs, which were then cut into 6 cm thickness wood blocks based on geographic directions. Wood blocks were divided into two groups. One group assigned as wet group and another group of wood blocks was air dried until their equilibrium moisture content reached to 8.6% and assigned as dry group. Density of all wood block was determined. Compression parallel to the grain and bending tests were carried out using Instron machine model 1186. Maximum stress (), proportional stress (), Modulus of elasticity parallel to the grain (EL), modulus of rupture (MOR), apparent modulus of elasticity (MOE) and real modulus of elasticity (E1) were determined. Effect of tree spacing, geographic directions and tree height on the above mentioned properties were analyzed using random factorial design. Results showed that Paulownia wood having dry density of 0.26 g/cm³ and apparent density of 0.28 g/cm³ is a very light wood. Also, its high strength to weight ratio places it in special category material for making light and strong constructions. In addition, its strength properties increases with the height of the tree. Especially this effect is more distinct by decreasing tree spacing. On the other hand, less tree spacing produces high strength wood and more wood material, as well.