The High forest of Ghana contains over 400 different timber species. Many of these have not been accepted as reliable building material. Limits to extending the range of species used for construction included not only lack of knowledge on the availability in sufficient volume but also lack of technical information on the lesser utilised species. The study investigates the properties of some of these lesser used species with promising physical and mechanical properties. Small clear samples prepared from sections of 3 species; Amphimas ptpterocarpoides (Yaya), Pterygota macrocarpa (Kyere), and Aningeria robusta (Asanfona) were tested in bending, compression, tension and shear and the axial variation of these within the trees.
Along the axis of the Amphimas pterocarpoides, the variation of compressive and shear strengths were not statistically significant. Mean values of the strength properties were found to be significantly higher than those of Milicia excelsa (Odum) the most commonly used species for construction.
For Pterogota macrocarpa, the mean normal density and compressive as well as tensile strengths were also found to be higher than those of Odum and most of the species used in construction. The wood was found to be highly susceptible to deterioration by insects and fungi. Slope of grain, knots and splits caused a reduction in strength.
The axial variation in all strength properties determined for Aningeria robusta was not statistically significant except for toughness. At 12% moisture content, all strength properties except maximum compressive strength parallel to the grain were higher than those of the Khaya spp. In certain structural applications Asanfona, Yaya and Kyere can be substituted for the primary species which are currently over exploited.
Key words: lesser-utilised, axial variation, mechanical property.
Correspondence: K. Frimpong-Mensah, Institute of Renewable Natural Resources, University of Science and Technology, Kumasi, Ghana
Telefax: +233-51-3137