Effect of Geometric Parameters of Finger Joint Profile on Ultimate Tensile Strength of Single Finger-Joined Boards

The feasibility of adopting a short finger profile for structural finger-joined lumber was studied by investigating the effect of geometric parameters of a finger joint profile on ultimate tensile strength (UTS) of single finger-joined boards. Six finger joint profiles were designed with three finger lengths (28.27, 15.88, and 12.70 mm). A commonly used finger profile was included as a control. Eastern white pine (Pinus strobus) lumber was used to fabricate single finger-joined boards that were joined using a polyvinyl acetate adhesive. Analysis of variance showed that the finger joint profile had a statistically significant influence on UTS of single finger-joined boards. Finger profile P2 showed the highest UTS value and had the shortest finger length among seven groups. With decreasing profile slope, UTS increased. Slope of 1:12 appeared to be the optimized value for finger jointing. UTS decreased with increasing tip width. It can be concluded that with the proper design of finger profile, a finger joint with short finger lengths can be used to fabricate finger-joined structural lumber without any loss of tensile strength compared with the finger length commonly used by the wood industry