Plywood properties influenced by the glue line

Summary The effect of the number and the location of glue lines in the cross section on the bending properties has been studied on plywood bonded with tannin-formaldehyde adhesive. The thickness of glue line has also been investigated. By comparing the theoretical equations with the empirical ones, we can get the thickness of the glue line of wattle tannin adhesive plywood to be 0.15 mm. As for Young's modulus in bending of the glue line in the plywood, it is calculated to be 219 800 kg/cm² and is larger than that of the glue line of phenolic resin bonded plywood. In relation to the veneer, Young's modulus of the veneer under the condition of plywood assembly seems to be slightly larger than that of the veneer under the free condition.The author wishes to express his gratefulness to CSIRO of Australia for a Fellowship during the tenure of which this research was carried out. The direction and cooperation of Mr. K. F. Plomley, Dr. P. Grossman and Mr. P. Collins, CSIRO of Australia are gratefully acknowledged