Structural Flakeboards and Composites 2967 



9 



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0,015 0.025 0.035 



FLAKE THICKNESS (INCH) 



Figure 24-34. — Relationship of flake thickness to modulus of elasticity of mixed-species 

 boards made from lathe flakes. Boards were 25 percent sweetgum, 25 percent hick- 

 ory, and 50 percent southern red oak. Flakes were 3 inches long. (Drawing after Hse 

 et al. 1975, from McMillin and Koch^) 



Flake width. — Further data from the McMillin-Koch experiment^ showed 

 that internal bond strength is significantly improved if lathe flakes of certain 

 species (e.g., sweetgum, hickory, and loblolly pine) are reduced in width after 

 they are formed on the shaping-lathe headrig. This eliminates very wide flakes 

 that fold (sweetgum and pine) or roll (hickory), causing poor resin distribution. 

 Horizontal density distribution is also generally improved by reduction of flake 

 width. 



Reduction offtake width did not improve MOE, however. These observations 

 suggest a three-layer board with random flake orientation in which core flakes 

 are narrow and face flakes are wider. In boards with oriented flakes in face 

 layers, narrow flakes (strands) are easier to align than wide flakes (wafers). 



