STRENGTH PROPERTIES OF YAYA (Amphimas pterocarpoides)

Joshua Ayarkwa

Forestry Research Institute of UST P.o. Box 63,Kumasi, Ghana

ABSTRACT - This paper presents the results of some strength properties of Yaya (Amphimas pterocarpoides), a lesser-known species of Ghana and compares them with those of Odum (Milicia excelsa) and European (Quercus spp.) which are well known structural timber species in Ghana and Europe respectively~ The results showed that at about 12% moisture content the has a density of 670kg/m3 with a mean modulus of rupture of 109 N/mm2, compressive strength parallel to the grain of 50 N/mm2, modulus of elasticity of 11600 N/mm2 and shear strength parallel to the grain of 16 N/mm2•

The strength properties in the present work suggest that the wood has a potential for utilisation in structural applications.

Keywords - Amphimas pterocarpoides, strength properties, structural applications

INTRODUCTION

According to Ghartey (1989),in the utilisation. It also compares the almost 82000 km2 results with published data on representing about 34% of the Odum and European oak. total area of Ghana, there exist over 420 species. However MATERIALS AND METHODS only about 50 of these species occur in export statistics for Wood samples for the investigation wood in Ghana (TEDB unpubl data). was obtained from two Currently .there is not enough collected from Akota in the technical data on many of the Asenanyo Forest Reserve in the Ghanaian species. The national Ashanti Region of Ghana. From each volume estimates has indicated , eight planks of dimensions, that several hardwood species are 55mm x 105mm x 3600mm were taken being under-utilised, whilst some from the butt, middle and top. primary species such as Odum are These were subsequently stacked over-exploited. (Ghartey 1989) under shed and air-dried for one week and later kiln-dried to about Yaya (Amphimas pterocarpoides) is 12% moisture content. The planks a ~esser-used species' which is were then re-sawn and dressed at abundant in the forest. However the wood workshop of the Forestry therets paucity of technical data Research Institute of Ghana into on its properties and possible 50mm x 50mm x 315mm strips. Fifty areas of utilisation~ lot is a defect free strips were randomly large tree of up to 3g::'m high and selected from the lot and prepared 2.7 m girth with small or no into 2em sections in buttress and clear cylindrica.l accordance with American Standard bole. The tree is normally found for Testing of Materials (ASTM) in the semi- (1979) specifi- cation D143-52. deciduous and evergreen forests of 30cm, Bem and 2cm lengths were cut Ghana. According to Irvine (1961), from the strips for the bending, its distribution in Africa ranges compression and shear tests from Guinea to and it is respectively. also found in Congo and . All the specimens were tested in This paper presents results of an accordance with the ASTM (1979) investigation of some strength specification using a 5000kg properties of the species in order Universal Testing Machine. The to determine possible areas of following strength properties were riII_ Journal of Forestry Vol.1 1994 57 Table 1: strength Properties of Yay a

12MOE6701160049.98 Moisture108.7. . ._- 16N/1lI112Kg/m3Coot>ression15.810N/1lI112DensityN/1lI112 11ShearN/1lI112Staticp'arr.parr.toBendinggral to grain efficient(%) Content % MOR 12 MeanVar. Co-

determined: modulus of rupture European Oak (690kg/ml). The (MOR), modulus of elasticity compressive strength of the three (MOE), compressive strength species were not significantly parallel to the ~rain and shear different. (Fig 1). strength parallel to the grain. Moisture content and density were also determined. Twenty specimens The bending strength (MOR) of Yaya were tested for each property. is about 27% and 19% higher than those of odum and oak RESULTS AND DISCUS~IONS respectively. The modulus of elasticity is about 16% >higher Mean values of the physical and than odum and 3% Qigher than Oak. mechanical properties were Yaya possesses superior shear calculated and are presented in strength to Odum and Oak, being Table 1. The results have also about 27% and 30% stronger been compared, with published data than Odum and Oak respectively. by Ashiabor (1968) on Odum and European oak at 12% moisture content (Fig 1). CONCLUSION

The results show that the strength properties of yay a compare favourably with those of odum and 1&;1 european oak however it is reported to be non-durable and requires. preventive measures for protection 100 against fungal and insect attack

," .,' before use. r'l'"'. , ", Yaya is widely distributed in the forest zone of Ghana and its 00 .' ' strength properties seem to justify its use for structural Q '','',&,''It'P, applications and for general 1::1(lOl.t.t constructional worki . ~·····l~'·l· ~...__~J~u:f'J, .. o O!,I( <::, j, ][ ':l:.Jlnp rrua m:r .h::er REFERENCES

Ashiabor, W.K.(1968) The properties of'Afzelia (Papao), Fig.1 Compnrnlivc Slrenglh~ of Ynya, Oak nnd Odum Anogeisseus leiocarpus; (Kane), Cynometra ananta (Anantaa), The results indicate that Yaya is ehie (Hyeduanini), a nigh density wood. Comparison of Tectona grandis (), Forest Ashiabor's 1968 data and the Products Research Institute present results show that the Technical Note No.6. 8pp density of Yaya is fairlr. similar to that ,of Odum (6S0kg/m) and

Ghana Journal of Forestry Vot.1 1994 58 ASTM (1979) Standard Method of University Press, London. p 352• Testing Small Clear Specimens of 353 Timber. 1979 Annual Book of ASTM Standards Part 22; Wood; Ghartey, K.K·.F.(1989) Results of Adhesives. Easton, USA. p 59-116. the Inventory. In Proc.of Ghana Forest Inventory Project Seminar Irvine, F.R. (1961) Woodv 29-30'~arch, 1989, Accra. 1989. of Ghana. London: Oxford p32.

GhanaJournal of Forestry Vol.1 1994 59