Structural Flakeboards and Composites 3043 



COMPOSITE PANELS AND MOULDINGS WITH VENEER FACES 

 OVER FIBER CORES 



Beyond the scope of this chapter, but probably of interest to readers, is Kelly 

 and Pearson's (1977) discussion of properties of panels with southern pine 

 veneer faces over fiberboard cores made from hardwood whole-tree chips. 



Also of potential interest is the technology of profile veneer wrapping of 

 medium-density fiberboard cores to fabricate large mouldings such as handrails 

 (Hall 1981). 



YIELDS OF HARDWOOD VENEER FOR COMPOSITE PANELS 



McAlister (1981) evaluated yields and grades of 0.160-inch-thick, 8-foot- 

 long, rotary-peeled veneer from yellow-poplar, white oak, and sweetgum 12 to 

 22 inches in dbh from the Georgia Piedmont and the mountains of North 

 Carolina. Also, McAlister and Clark'^ conducted a similar study of black tupelo, 

 sweetgum, and yellow-poplar from the Coastal Plain of South Carolina. Results 

 of these studies are shown in tables 12-5 through 12-10. McAlister (1981) 

 summarized his Piedmont-mountain area study by noting that a typical mix of 

 100 yellow-poplar, sweetgum, and white oak trees 12 to 20 inches in dbh and 

 containing 3008 cu ft of stemwood to a 4-inch top, yielded about 375 cu ft of dry 

 C-grade and better 1/6-inch veneer; D-grade veneer from these trees totalled 

 another 233 cu ft. A typical mix of 100 trees 12 to 20 inches in diameter of the 

 species studied in the Coastal Plain had stemwood volume to a 4-inch top (dib) 

 of 3,207 cu ft and yielded 61 8 cu ft of dry C-grade and better veneer, and 259 cu 

 ft of D-grade veneer. Water oak from the Coastal Plain was eliminated from the 

 study because fully half of the stems had severe butt rot extending from the 

 stump upwards 4 to 6 feet. (See table 24-31 for mechanical properties of these 

 veneers.) 



24-20 COMPOSITE PANELS WITH FLAKE FACES OVER 



VENEER CORES 



For some panel uses, linear expansion across one or both dimensions of a 

 structural or decorative panel is critical. Elmendorf (1961) suggested a proce- 

 dure for pressing composite panels with flake faces over a solid lumber or veneer 

 core to exploit the properties of naturally aligned fibers in solid wood. 



Suchsland et al. (1979) described a fabrication procedure (fig. 24-54) in 

 which low-grade veneer in single or double plys was used as a core and random- 

 ly placed, 3-inch-long, 0.015-inch-thick sweetgum flakes cut on a shaping-lathe 

 were used as faces; in their experiment southern pine veneer 1/10-inch thick was 



McAlister, R. H., and A. Clark III. Manuscript in preparation. Veneer yields by grade from 

 three Coastal Plain hardwoods — blackgum, sweetgum, and yellow-poplar. Southeast. For. Exp. 

 Stn., U.S. Dep. Agric, For. Serv., Asheville, N.C. 



