The Variability between the Strength and Some Physical Properties of Allanblackia Parviflora for Furniture Production

In Ghana, many of our traditional wood species are over exploited and threatened to extinction. The utilization of other lesser-used and lesser known wood species needs to be looked at urgently as a possibility of increasing the wood resource base. And a successful expansion of the resource base is dependent on adequate knowledge of the properties of the lesser-used species such as Allanblackia parviflora which can be a good substitute to the dwindling species. It was against this background that the strength and some physical properties of Allanblackia parviflora trees were determined to predict the suitability of the species for furniture production and as a structural raw material for downstream production of wood products. Three Allanblackia parviflora trees were extracted from a cocoa farm a moist semi-deciduous forest at Powuako near Ayanfuri in Western Region because of the known age of trees from plantation. Logs from the trees were converted to boards. One-half of the boards were used in the green state for the determination of the green moisture content, basic density and the mechanical tests. And the other half, air dried for mechanical tests. Mechanical strength test specimens were prepared and tested in accordance with the British Standard BS 373: 1957. Mean green moisture content was 81.19%. Mean basic density was 539.00kg/m3. The range of mean strength values in N/mm2 in the ‘green’ [and dry (12 % mc)] conditions for the three wood species were as follows: - Modulus of Rupture: 50.00 - 56.00 [85.00 - 94.00], Modulus of Elasticity: 6,387.00-6,951.00 [8,287.00 - 8,875.00], compression parallel to grain: 24.00-28.00 [13.00-14.00] and shear parallel to grain 6.83-7.74 [9.62-10.82]. Mean ratios of dry to ‘green’ MOR and MOE were 1.68 and 1.28. Allanblackia parviflora wood can be used for furniture production. In finding the variations among and within the three trees of Allanblackia parviflora, there are differences but these differences are not significant (p-value >0.001) among the tree. But for variations within tree-sawn planks [heart to sap division 1, 2, 3] indicates that, the strength of division one (1) and two (2) are higher than division three (3).Almost all strength tests conducted shows a consistent trend that, the heartwood portion of each division is slightly stronger in terms of resistance to failure than its corresponding sapwood portion. Based on the strength tests results, division one (1) and two (2) can be described as the heartwood portion and division three (3) as sapwood portion. Comparing the strength of Allanblackia parviflora to an existing classification (grade), strength is ‘medium’ in Allanblackia parviflora wood. And this predicts the suitability of Allanblackia parviflora wood for furniture production. It is recommended that, other strength and physical properties such as hardness, cleavage and shrinkage tests are determined to obtain detailed information about the species in order to further predict their performance as structural raw materials for furniture production. Indeed, it is a good substitute to the dwindling (scarlet star) species, and will increase the wood resource base. It should be considered as exploitable raw material base for timber industries by stakeholders in wood industry.

Source: KNUST