STRENGTH PROPERTIES OF YAYA (Amphimas pterocarpoides)

Joshua Ayarkwa

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

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

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

Keywords - Amphimas pterocarpoides, strength properties, structuralapplications

INTRODUCTION

According to Ghartey (1989),in thealmost 82000 km2 forest zonerepresenting about 34% of thetotal area of Ghana, there existover 420 hardwood species. Howeveronly about 50 of these speciesoccur in export statistics forwood in Ghana (TEDB unpubl data).Currently .there is not enoughtechnical data on many of theGhanaian species. The nationalvolume estimates has indicated

that several hardwood species arebeing under-utilised, whilst someprimary species such as Odum areover-exploited. (Ghartey 1989)

Yaya (Amphimas pterocarpoides) isa ~esser-used species' which isabundant in the forest. Howevertherets paucity of technical dataon its properties and possibleareas of utilisation~ lot is alarge tree of up to 3g::'m high and2.7 m girth with small or nobuttress and clear cylindrica.lbole. The tree is normally foundin the semi-

deciduous and evergreen forests ofGhana. According to Irvine (1961),its distribution in Africa rangesfrom Guinea to Cameroon and it isalso found in Congo and Sudan.

This paper presents results of aninvestigation of some strengthproperties of the species in orderto determine possible areas of

riII_ Journal of Forestry Vol.1 1994

utilisation. It also compares theresults with published data onOdum and European oak.

MATERIALS AND METHODS

Wood samples for the investigationwas obtained from two treescollected from Akota in theAsenanyo Forest Reserve in theAshanti Region of Ghana. From eachtree, eight planks of dimensions,55mm x 105mm x 3600mm were taken

from the butt, middle and top.These were subsequently stackedunder shed and air-dried for oneweek and later kiln-dried to about

12% moisture content. The plankswere then re-sawn and dressed at

the wood workshop of the ForestryResearch Institute of Ghana into50mm x 50mm x 315mm strips. Fiftydefect free strips were randomlyselected from the lot and preparedinto 2em square sections inaccordance with American Standardfor Testing of Materials (ASTM)(1979) specifi- cation D143-52.30cm, Bem and 2cm lengths were cutfrom the strips for the bending,compression and shear testsrespectively.

All the specimens were tested inaccordance with the ASTM (1979)specification using a 5000kgUniversal Testing Machine. Thefollowing strength properties were

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Table 1: strength Properties of Yay a

MoistureDensityCoot>ressionStatic BendingShear parr.

Contentp'arr. to gral to grain

MOR

MOE._-.

%Kg/m3N/1lI112 N/1lI112N/1lI112N/1lI112

Mean

1267049.9 108.71160015.8

Var. Co-

.12 8 111016efficient(%)

determined: modulus of rupture(MOR), modulus of elasticity(MOE), compressive strengthparallel to the ~rain and shearstrength parallel to the grain.Moisture content and density werealso determined. Twenty specimenswere tested for each property.

RESULTS AND DISCUS~IONS

Mean values of the physical andmechanical properties werecalculated and are presented inTable 1. The results have also

been compared, with published databy Ashiabor (1968) on Odum andEuropean oak at 12% moisturecontent (Fig 1).

European Oak (690kg/ml). Thecompressive strength of the threespecies were not significantlydifferent. (Fig 1).

The bending strength (MOR) of Yayais about 27% and 19% higher thanthose of odum and oakrespectively. The modulus ofelasticity is about 16% >higherthan odum and 3% Qigher than Oak.Yaya possesses superior shearstrength to Odum and Oak, beingabout 27% and 30% strongerthan Odum and Oak respectively.

CONCLUSION

1&;1

100

r'l'"," .,''. ,

The results show that the strengthproperties of yay a comparefavourably with those of odum andeuropean oak however it isreported to be non-durable andrequires. preventive measures forprotectionagainst fungal and insect attackbefore use.

00

<::,

",

~·····l~'·l·

.' '

j, ][':l:.Jlnp rrua m:r

. f'J, ..~..__~J~u:.h::er

Q '','',&,''It'P,

1::1(lOl.t.to O!,I(

Yaya is widely distributed in theforest zone of Ghana and its

strength properties seem tojustify its use for structuralapplications and for generalconstructional worki .

Fig.1 Compnrnlivc Slrenglh~ of Ynya, Oak nnd Odum

The results indicate that Yaya isa nigh density wood. Comparison ofAshiabor's 1968 data and the

present results show that the

density of Yaya is fairlr. similarto that ,of Odum (6S0kg/m) and

Ghana Journal of Forestry Vot.1 1994

REFERENCES

Ashiabor, W.K.(1968) Theproperties of'Afzelia (Papao),Anogeisseus leiocarpus; (Kane),Cynometra ananta (Anantaa),Guibourtia ehie (Hyeduanini),Tectona grandis (Teak), ForestProducts Research InstituteTechnical Note No.6. 8pp

58

ASTM (1979) Standard Method ofTesting Small Clear Specimens ofTimber. 1979 Annual Book of ASTMStandards Part 22; Wood;Adhesives. Easton, USA. p 59-116.

Irvine, F.R. (1961) Woodv Plantsof Ghana. London: Oxford

GhanaJournal of Forestry Vol.1 1994

University Press, London. p 352­353

Ghartey, K.K·.F.(1989) Results ofthe Inventory. In Proc.of GhanaForest Inventory Project Seminar29-30'~arch, 1989, Accra. 1989.p32.

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