Influence of wood defects on some mechanical properties of two tropical Ghanaian hardwoods

Effects of slope of wood grain, knot, split, ingrowth and sapwood on some mechanical wood properties of Pterygota macrocarpa (Kyere) and Piptadeniastrum africanum (Dahoma) have been studied, using structural size specimens and a 60 tonne structural wood testing machine. The study on the two tropical hardwoods indicated that slope of wood grain has negative correlation with wood strength and modulus of elasticity, and the effect seems to be more pronounced in tension than bending and compressive strengths of the wood. Scattered knots were found to reduce wood strength and stiffness. Splits were also found to reduce wood strength, but stiffness was not significantly affected. Ingrowth and sapwood were both found to reduce wood strength more than stiffness. Within the limits of the results of the study, it may be concluded, generally, that the wood defects and growth characteristics studied have strength-reducing influences on the strength and modulus of elasticity of tropical hardwoods. The extent to which these wood defects affect the wood properties, however, varies depending on the size and position of the defect. Thus, the actual behaviour of wood cannot be reliably determined from small clear wood specimens. This paper presents results of the study, indicating the effects of the wood defects and growth characteristics studied on the strength and modulus of elasticity of the two tropical hardwoods. JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 1 Number 2, January (1999) pp. 131-14