Properties of structural plywood from southern red oak and mixtures of southern oak, sweetgum, and southern pine

This paper investigates the mechanical properties of southern red oak plywo od and mixtures of southern red oak with sweetgum and southern pine that we re bonded with a commercial extended phenolic resin. The results indicate t hat the MOE and MOR values of 3-ply specimens of all groups with face grain parallel to span, as expected, are higher than corresponding values of 4-p ly specimens. The MOE and MOR values of 4-ply specimens of all groups with face grain perpendicular to span, as expected, are more than two times high er than corresponding values of 3-ply specimens. All 3-ply and 4-ply cycled (wet-dry) specimens of all species combinations retained between 80 and 95 percent of their original MOE values and between 72 and 99 percent of thei r original MOR values. The level of property retention after cycling is ind icative of the quality of bonding. The plate shear moduli of 4-ply specimen s in all moisture conditions are 50 percent higher than corresponding 3-ply specimens. The edgewise shear strength of 4-ply specimens with all-oak ven eers in all moisture conditions are also considerably higher than the corre sponding 3-ply specimens. The glueline shear strength of all-oak specimens retained 85 percent of the original value after wet-dry cycling. The percen t of wood failure, however, was reduced from 50 percent in the original to 25 percent after cycling.