Void Volume Wood: An Any Tree-Whole Tree Concept

Complex stand heterogeneity of wet-evergreen tropical forests, with 40-80 percent of the volume in timber with air-dry densities over 0.8 g per cc, demands other than conventional approaches in forest products utilization research. One such approach, the development of void volume wood as a part of any tree-whole tree use concept, is presented. Green lumber, particularly the heavy hardwoods, could receive varying patterns of microscopic lightening holes (voids) to yield boards with uniform moderate densities. Beams were fabricated and tested in bending to determine the effect of maintaining the net section but reducing hole diameters and the effect of reducing the net section but maintaining hole diameter (diameter ranged from 1/8 inch to 1/2 inch). There was no significant difference in modulus of rupture between the controls and the several perforation patterns. Thus, the effect of minute holes on bending strength, now inconvenient to test, is predictable by conventional flexure formula. A dense tropical wood with a basic specific gravity of 0.90 could be perforated with 1,000 1/64-inch diameter holes per square inch and still have an allowable stress in bending of 2,600 psi. The applicability of rapid press-drying, chemical diffusion treatments, and microencapsulated compounds to void volume wood is suggested.

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