Identification of the best finger joint configuration for Sri Lankan wood species based on the flexural strength.

Abstract

Finger joint technique is used to eliminate defects in sawn wood planks, since such defects reduce the strength of the planks. This study was, therefore conducted to find the finger joint configuration that is best suited for seven species of wood, namely Grandis (Eucalyptus grandis), Jack (Artocarpus heterophyllus), Kumbuk (Terminalia arjuna). Mahogany (Swietenia macrrophylla), Pine (Pinus caribaea), Satin (Chloroxylon swietenia) and Teak (Tectona grandis) which are mostly used in Sri Lanka in the manufacture of furniture. The tests were carried out on vertically and horizontally finger-jointed timber samples (with 13 mm and 19 mm finger lengths) made of two sections bonded with an adhesive containing polyvinyl acetate. The variation of the flexural strength of the samples with the orientation and finger length of the samples was studied and the modules of rupture (MOR) and modulus of elasticity (MOE) of the samples were also measured. BS 373 (1957) was the standard used for the flexural tests. A universal testing machine (UTM 100 PC) was used for the mechanical tests. Duncan’s multiple range test was used at a significant level of 0.05 to separate the means of MOR’s and MOE’s measured. The highest MOR and MOE were observed in horizontally oriented wood samples with 19 mm long fingers. Finger joint manufacturers in Sri Lanka will find the findings of this study useful.