From residue to structurally and economically valuable lumber: Assessment of density, flexural properties, and joint efficiencies of finger-jointed logging residues of Khaya Ivorensis

Abstract

One way to reduce forest depletion rate and increase timber availability is to turn logging residues into structurally and economically valuable timber, and finger-jointing (FJ) appears the best technology to adapt. This study centred on Khaya ivorensis with five-fold objectives of assessing the: density; flexural properties; moisture content (MC) and FJ combination effect on density and flexural properties; joint efficiencies in MOE and MOR; and the predictive accuracy of density and MC for MOE and MOR following ISO 3131 − 1975 (for density), and BS 373–1957 (for flexural properties). Branch and stem off-cuts were extracted from two natural forest reserves and finger-jointed at two MCs (18 ± 3%mc and 9 ± 3%mc) using polyvinyl acetate adhesive (PVA). All FJ lumber at 18%mc, and branch & branch FJ lumber at both MCs were significantly (P < 0.05) denser than the rest. All FJ lumber at 18% MC were elastic than their unjointed stemwood. Though branch & branch FJ exhibited lowest elasticity and rupture at both MC levels, samples at 18% MC significantly (P < 0.05) exhibited lower rupture than those at 9%MC. MC and FJ lumber combination significantly (P = 0.000) influenced density and flexural properties. MC and density predicted flexural properties to about 79% accuracy. Relative to their unjointed stemwood, FJ lumber at 18%MC gained over 100% elasticity but had 40 to 70% MOR and 67 to 90% MOE at 9%MC. In conclusion, Finger-jointing branchwood with PVA is possible, but for optimum flexural properties, branch & stem combinations rather than branch & branch are recommended.