Effect of span depth ratio on the bending properties of plywood

摘要

Investigations were carried out to study the effect of span depth ratio (span length:thickness) on bending properties viz, modulus of elasticity (M_oE) and modulus of rupture (M_oR) of plywood. All the three grades of plywood viz. Boiling water proof(BWP), boiling water resistant (BWR) and moisture resistant (MR) were tested and evaluated for M_oR and M_oE at different span depth ratios of 10:1, 20:1, 32:1 and 48:1 in along the face grain direction and 10:1, 16:1, 20:1 and 24:1 in across the face grain direction, respectively, to study the variation in results because of change in span depth ratio. The results were generalized for all types of plywood viz. MR, BWR and BWP, irrespective of initial raw materials and processing conditions. The results revealed that the bending properties of plywood are in the same range at span depth ratio of greater or equal to 20, whereas reduction of 5-30 % in the values of bending properties was observed for the plywood tested at span depth ratio of 10 as compared to plywood tested at span depth ratio of 20.