Study on the Bending Strength of Solid and Glue-Laminated Timber from Three Selected Nigerian Timber Species

Abstract

Structural timber is desirable for lightness, aesthetics and environmental friendliness. However harnessing timber for structural application can be daunting. Over decades, developed societies modified their sawn timber species by way of gluing in the forms of glued laminated beams and columns. In Nigeria, sawn timber is yet to be explored along these lines. This paper therefore assessed the suitability of Funtumia africana, Alstonia congensis and Antiaris toxicaria Nigerian timber species in the production of glue- laminated timber elements using polyvinyl acetate glue.  The glueability, physical and mechanical properties of solid and glue-laminated species were assessed and compared.  Bending strength and characteristic values of bending strength were determined. Results showed that the timber species were glueable and bending strength across the species was 65.22 N/mm² vs 36.44 N/mm²; 26.15 N/mm² vs 25 N/mm²; 14 N/mm² vs 20 N/mm² in solid vs glued laminated Funtumia Africana, Alstonia congensis and Antiaris toxicaria beams respectively in edge wise bending. The glued laminated elements across the species developed 55%, 95% and 143% of the solid wood strength. It was shown that the timber species were structurally glueable using polyvinyl acetate glue. The study has shown that the bending strengths of glue-laminated Nigerian timber species were of structural significance given the bending strength of 36.44 N/mm², 25 N/mm² and 20 N/mm² in Funtumia africana (Ire), Alstonia congensis(Awun) and Antiaris toxicaria (Oriro).

Keywords: Glueability, Glued laminated timber, Nigerian timber species, bending strength