Composite Plywood with Southern Pine Veneer Faces and Oriented Strand Core from Sweetgum and Southern Pine

Certain mechanical properties and dimensional changes of 1/2 in. composite plywood, fabricated from 1/8 in. southern pine veneer faces and 1/4 in. unidirectionally oriented strand cores were evaluated. Three types of cores were included: (a) 100% southern yellow pine, (b) 100% sweetgum, and (c) a mixture of 50% southern pine and 50% sweetgum. The cores were blended with a liquid phenolformaldehyde resin (6 1/2% solids) and bonded to veneer faces with an extended phenolic glue.Experimental results indicate that the physical and mechanical properties of the composite panels were equal to and, in certain cases, superior to 1/2 in. southern pine CDX plywood and to commercial composite plywood from western species.After comparing the experimental results of the composite panels with similar properties of commercial CDX southern pine plywood, the following conclusion can be drawn: Composite panels similar to those tested are expected to perform satisfactorily all structural functions required by sheathing panels for walls, roofs, and subfloors

Hygroscopic Properties and Shrinkage of Southern Yellow Pine Plywood

Five constructions of southern yellow pine plywood, unidirectionally laminated veneer, and loblolly pine solid wood were used for investigation of hygroscopic properties at several RH conditions. EMC values of the southern yellow pine plywood between 20% RH and 90% RH were approximately 1% lower than corresponding values of loblolly pine solid wood. Most plywood panels shrank less along the face grain than across. From water-soaked condition to about 4.5% MC, thickness shrinkages of plywood varied from 7% to 9% while length shrinkages were always less than 1% except for 1/2-inch, 4-ply plywood. The ratio of number of glue lines to plywood thickness influenced thickness and volume shrinkage. Plywood with a higher ratio had a tendency to shrink less. FSP values were determined by two intersection point methods-one with volumetric shrinkage, the other with MOE. The respective approximate FSP values were 28.7% and 27.3% MC for plywood, and 31.0% and 27.5% for solid wood