3048 Chapter 24 



Hunt (1975) showed that waferboards have in-plane shear modulus more than 

 2.5 times greater than plywood, and Price (1978) found that at 46 Ib/cu ft, the 

 plate shear modulus of random-oriented mixed southern hardwood flakeboard 

 was 259,000 psi. (See discussion related to table 24-15). Woodson (1981) 

 showed that 1/8-inch-thick, rotary-peeled hickory veneers — even in short 

 lengths — can be parallel-laminated into very high-strength flange material; 

 bending properties he observed in specimens of such material measuring 2 by 2 

 inches square and 48 inches long were as follows (at about 1 1 percent moisture 

 content): 



Species 

 and veneer length MOE MOR 



Psi 



Hickory veneer 12 inches long; distributed pattern of butt 



joints 1,759,000 13,230 



Hickory veneer 48 inches long; no butt joints 1,882,000 18,735 



Southern pine veneer 48 inches long; no butt joints 1,680,000 12,684 



These findings indicate that it should be possible to make a high-strength I- 

 beam from hardwood flange veneers and hardwood flakeboard (fig. 24-57); 

 when utilizing such high-strength hardwood flanges in composite joists, webs 

 must be thicker — to preclude buckling failures — than those used with weaker 

 flanges. Woodson (1981) and Koch (1982) have provided economic analyses of 

 such operations. These analyses are summarized in sections 28-21 and 28-31. 



R. H. McAlister (table 24-31) evaluated tensile properties of dry rotary- 

 peeled, defect-free veneer of four major southeastern hardwood species. Aver- 

 age modulus of elasticity measured in tension varied from 1,370,000 psi for 

 Piedmont sweetgum to 1,740,000 psi for Piedmont yellow-poplar. Average 

 tensile strength varied from about 3 ,000 psi for Coastal Plain woods and moun- 

 tain white oak, to about 7,000 psi for yellow-poplar and white oak from the 

 Georgia Piedmont (table 24-31). 



24-22 COMPLY LUMBER 



Figure 24-57 depicts a composite I-beam made with high-strength, parallel- 

 laminated hardwood veneer flanges and a thin web of hardwood structural 

 flakeboard. It is possible to use a weaker, but thicker, particleboard web and 

 flanges comprised of as few as two layers of veneer to fabricate composite studs 

 and joists (fig. 24-58). 



McAlister (1979) made such studs — trade-named COM -PLY — with veneers 

 of yellow-poplar, sweetgum, and white oak. Two 1/6-inch-thick veneers were 

 parallel laminated to each edge of a phenolic-bonded particleboard having aver- 

 age density of 40 Ib/cu ft and measuring 1.5 by 2.83 inches; the composite studs 

 therefore measured 1.5 by 3.5 inches in cross section. McAlister found that 

 these studs met performance requirements described by Blomquist et al. (1976) 

 and that they were comparable to similar composite studs made with southern 

 pine veneers and with kiln-dried, stud-grade southern pine lumber. 



