Bending Strength Classification of Some Common Nigerian Timber Species

Abstract

This paper was aimed at the EN338 (2009) strength classification of some common Nigerian timber species, namely; Strombosia pustulata, Macrocarpa bequaertii, Nauclea diderrichii and Entandrophragma cyclindricum. Twelve (12) timber planks from the selected species were supplied from Ekiti state in the southern part of Nigeria. The specimens for experimental measurements were prepared from the obtained timber planks. Laboratory experiments were conducted to determine the physical and mechanical properties of the selected timber species in accordance with EN408 (2003). The mechanical properties were determined using four point bending test. The generated properties were used to obtain the characteristic values of the material properties in accordance with EN384 (2004). The selected timber species were then graded in accordance with EN 338 (2009). Strombosia pustulata, Macrocarpa bequaertii, Nauclea diderrichii and Entandrophragma cyclindricum were assigned to strength classes D35, C14, D30 and D18, respectively. Other properties such as tensile and compressive strengths parallel and perpendicular to grains, shear strength as well as shear modulus were computed from the empirical relationships given in EN 338.