Bending Strength of Finger-Jointed Lamellae from Laran Plantation Timber Species

In designing the engineered timber products such as glued laminated timber (glulam) and cross-laminated timber (CLT), the finger-jointed strength data for lamellae are required and mentioned in BS EN 14080:2013 and BS EN 16351: 2015, respectively. However, the strength data presented in these standards are primarily derived from European timber and their applicability to tropical plantation timber remains uncertain. Thus, this paper presented the flatwise and edgewise finger-jointed bending strength of Malaysian plantation species namely Laran (Neolamarckia Cadamba). Four-point bending tests were conducted in accordance with BS EN 408:2010 on finger-jointed specimens. A total of 100 specimens were prepared for flatwise and edgewise tests with dimensions of 40mm x 135mm x 950mm and 40mm x 135mm x 2700mm, respectively. The finger joints with 12mm finger length located at the centre of each lamellae were bonded using phenol-resorcinol formaldehyde (PRF) adhesive. The characteristic bending strength was calculated according to BS EN 384:2016. The results indicate a mean modulus of rupture (MOR) of 60.42 N/mm² for flatwise and 29.52 N/mm² for edgewise bending. The characteristic finger-joint bending strength were determined to be 21.56 N/mm² for flatwise and 17.44 N/mm² for edgewise. The predominant failure modes observed were splitting at the finger base (57% for flatwise) and shearing (78% for edgewise). These findings provide valuable data for early classification of finger-jointed bending strength in flatwise and edgewise direction, contributing to the design of glulam beams and CLT panels.