DEVELOPMENT OF A MATERIAL-EFFICIENT FINGER-JOINT PROFILE FOR STRUCTURAL FINGER-JOINED LUMBER

摘要

Finger-joined lumber is widely used for structural applications such as glued-laminated timber and I-joists. In North America, the length of a structural finger-joint is between 22 mm (7/8 in) and 29 mm (1-1/8 in), which is longer than that adopted in some countries. Adopting a shorter finger-joint length would result in less waste of good quality lumber and possibly the less use of adhesive. This study was aimed at developing a material-efficient finger-joint profile for structural finger-joined lumber with minimal influence on joint strength. A new joint profile of 12.7 mm (1/2 in) in length was developed. Lumber grade and cutter sharpness were considered. 2x3 (38 mm thick and 63 mm wide) lumber was used to fabricate 8 groups of 2.44 m (8') long finger-joined lumber specimens. Two groups of unjoined lumber were used as controls. The adhesive used was a two-part polyurethane. The key findings from this study were that the optimized cutters of 12.7 mm (1/2") in length could produce the finger-joined lumber of better-than-expected quality in terms of modulus of elasticity (MOE) and ultimate tensile strength (UTS) and the bonding quality was satisfied in terms of delamination resistance values (less than 5%). These results suggest that adoption of a short finger joint profile is feasible for Canadian engineered wood products manufacturers to produce finger-joined lumber for structural applications.