Treesearch

“This report presents curves of coefficients and formulas for use in calculating the buckling of flat panels of sandwich construction under edgewise compressive loads. The curves were derived for sandwich panels having one facing of either of two orthotropic materials, the other facing of an isotropic material; both facings of orthotropic material; both facings of isotropic material; and cores of orthotropic or isotropic material. Parameters are chosen so that facings may be of different thicknesses and so that isotropic facings can also be of different isotropic materials. Curves were...

A major loss sustained by small mills results from inaccurately cut lumber. Such lumber sells only at reduced prices and encounters stiffer sales resistance than lumber from the more accurately cutting band mills. A less apparent loss is the excessive loss of material that results from inaccurate cutting.

Veneer, plywood, and flakeboard specimens were subjected to various humidity conditions. Physical and elastic properties of the veneer were determined and the influence of these properties on the movement of plywood and flakeboards fabricated of like material was evaluated, The linear movement of the plywood and flakeboards was closely related to the longitudinal-to-grain movement of the veneer.

Experimental work was undertaken to investigate the extent and magnitude of deterioration that can occur in typical plywood-to-lumber glue joints subjected to stresses resulting from changes in the moisture content of the wood, and to compare the performance of a somewhat flexible or deformable adhesive to that of a rigid adhesive in these joints. Results showed that the degradation of lumber-to-plywood joints can be very severe as a result of one cycle from 80° F. and 30 percent relative humidity, to 80° F. and 97 percent relative humidity, returning to a low moisture condition. Failure...

From the earliest days of exploration and colonization in tropical America, Spanish-cedar has been one of the most important timber trees of the area. The wood became an article for the export trade during the 1800’s when the cigar industry demanded the use of Spanish-cedar for packing cigars. These fragrant boxes were commonplace before rising costs in the 1930’s finally forced the cigar industry to turn to paperboard or less expensive containers manufactured from soft native lumber. Spanish-cedar remains to this day as one of the most valued trees for local use in Latin America. In the...

Shrinkage, specific gravity, and hardness of two shipments of silk-oak (Grevillea robusta) from Hawaii were evaluated to provide basic information pertinent to the use of the wood for cabinet and furniture purposes. The wood resembles Hawaii-grown shamel ash (Fraxinus uhdei ) in the properties evaluated. Shrinkage compares well with that of black cherry, silver maple, or red lauan. Side hardness of green wood considerably exceeds that of black cherry and paper birch, but that of air-dry wood is closely comparable to that of those two Mainland species. End hardness of green wood compares...

Tear tests made on low-finish bond paper and a 42-pound linerboard showed that the tear resistance, the degree of spreading of the plies, and the deviation from a straight line of failure increased with the increase in the number of plies tested. Tests on plies of aluminum foil indicated this degree of variation due to multiplicity of plies lay not in the tester but in the type of material being tested. With foil, no increase in tear resistance per ply accompanied the increase in the number of plies tested. But when the aluminum foil plies were separated by bulking and tested, results...

A direct-reading strain gage has been developed at the U.S. Forest Products Laboratory that provides rapid and accurate measurement of the stress - strain properties of paper. The gage, which employs a differential transformer, is particularly suited to servo-operated x-y recorders.

In 1959, a new technique was devised at the Forest Products Laboratory that provided a means of examining, evaluating, and recording the show- through pattern (often called telegraphing) of panels made with particle board cores. Although the technique was devised as a working tool to evaluate show-through characteristics of particle board cores, it can be used equally well on anyfurniture panel, regardless of color, pattern, or type of core, provided the surface is finished with a satin (or brighter) finish. This means that the technique has potential applications far beyond the original...

Douglas-fir is one of the largest, most abundant and widely distributed species of trees native to North America, and next to the southern yellow pines, it is cut in the greatest quantities of any wood of commercial importance. It belongs to the coniferous family and is, therefore, a softwood. Other names for Douglas -fir are red fir, yellow fir, Oregon pine, Puget Sound pine, red pine, red spruce, and Douglas spruce. Its botanical name is Pseudotsuga menziesii (Mirb.) Franco.