Structural Flakeboards and Composites 2965 



LATHE FLAKES (PERCENT) 



inn 

 8 



50 100 



VENEER FLAKES (PERCENT) 



Figure 24-32. — Relationship of modulus of elasticity to proportions of veneer and lathe 

 flakes in 1/2-inch sweetgum flakeboard with density of 42 pounds per cubic foot. 

 (Drawing after Price 1974.) 



flake length to the range from 1 to 3 inches to ease flake handling problems. At 

 the Pineville, La. laboratory of the Southern Forest Experiment Station, re- 

 searchers repeatedly have shown the superiority in face layers of 3-inch-long 

 flakes cut 0.015 inch thick (length-to-thickness ratio of 200); 3-inch-long core 

 flakes cut 0.025 inch thick also contribute more to panel stiffness than 1 .5-inch 

 flakes of this thickness (fig. 24-33 top). It is difficult to cut flakes thinner than 

 0.015 inch on industrial flaking equipment; an L/T ratio of 3/0.015 = 200 

 therefore seems near the practical maximum for face-layer flakes. 



McMillin and Koch^, in a study of flakeboards made from mixed-species, 3- 

 inch-long lathe flakes of sweetgum, hickory, and southern red oak, showed that 

 MOE was maximum with flakes 0.015 inch thick (fig. 24-34), but that internal 

 bond strength was maximum with 0.025-inch-thick flakes. In boards made of 

 each of these species, and also of loblolly pine, the same relationship prevailed. 

 A three-layer board having 0.015-inch-thick face flakes and 0.025-inch-thick 

 core flakes should achieve near optimum MOR and MOE, with acceptable IB. 



McMillin, C. W., and P. Koch. 1974. Properties of homogeneous exterior structural boards 

 made from southern hardwood and loblolly pine flakes cut on a Koch lathe. U.S. Dep. Agric, For. 

 Serv., South. For. Exp. Stn., Alexandria, La., Fin. Rep. FS-SO-3201-2.67, dated Aug. 26, 1974. 



