VARIATIONS OF MECHANICAL PROPERTIES IN PLANTATION TIMBERS OF JELUTONG (DYERA COSTULATA) AND KHAYA (KHAYA IVORENSIS) ALONG THE RADIAL AND VERTICAL POSITIONS

Thoroughgoing efforts are regularly being carried out for the development and promotion of plantation timbers. Continuous acquisition of physical and mechanical data will ensure the utmost utilisation of these timbers. Knowledge in variation of mechanical properties of plantation timbers at different positions in a tree is important for the successful use of the timber as a solid material. The present study used young plantation trees to obtain basic information on the appropriate uses of thinning materials (i.e. trees cut down during thinning). Jelutong (Dyera costulata) and khaya (Khaya ivorensis) aged 10 and 15 years old respectively were selected as samples. Mechanical analyses were conducted based on radial positions from pith to bark and vertical positions of bottom, middle and top logs. Evaluations were made based on the modulus of rupture, modulus of elasticity, compressive strength parallel to the grain, shear strength parallel to the grain, tensile strength parallel to the grain, Janka hardness and specific gravity. Mechanical properties of jelutong and khaya along the radial and vertical positions were not symmetry. Nevertheless, some noticeable patterns of the mechanical properties relative to the radial and vertical positions were observed.