Abstract: [Objective] In order to obtain the optimization processing parameters of finger-jointing, the relationship of tenon's end pressure (finger-jointing pressure), fitness ratio and it's type was clarified, and the impact of tenon type, fitness ratio and finger-jointing pressure on its mechanical properties was also investigated.[Method] Using five different types of cutter to process Larix gmelinii lamina into vertical type finger-jointing tenon with different fitness ratio. Pressing two finger-jointing tenons together until the addendum contacts the groove bottom closely at mechanical machine, obtaining the value of pressure (ten couples test sample with different types and fitness ratio was used), and the relationship between the finger-jointing pressure with tenon type parameters and fitness ratio was clarified. Gluing the finger-jointing tenon manually (both surfaces were glued with consumption of 180 g·m^-2), then pressing them together with the value of pressure, tenon type and fitness ratio we obtained frontally. After 24 hours, the elastic modulus, static bending strength and tensile strength of the finger-jointing tenon were test using the method of chapter 5.3.3 and 5.4, the experiment of bending and tensile strength in the book of structural glued laminated timber, the GB/T 26899-2011. Ten specimens for each tenon type and fitness ratio were available for testing. Half of them were used for elastic modulus and static bending strength testing, the rest was used for tensile strength testing. The influences of tenon type, fitness ratio, finger-joint pressure on its adhesive bonding mechanical property were disussed, and the optimization adhesive bonding parameters of finger-jointing technique were obtained.[Result] The finger-jointing pressure significantly increased with the increase of fitness ratio. However, the relationship between the fitness ratio and finger-jointing pressure was not always the same and depend on tenon type (consisting of finger length, finger angle, pitch, and alveolus width). There were pronounced difference among the influence of fitness ratio on finger-jointing mechanical properties (the elastic modulus, the static bending strength and the tensile strength) with various tenon types. All kinds of tenon exhibited better mechanical properties when the finger-jointing pressure was 8-15 MPa, and the value increased proportionally with the increase of finger length.[Conclusion] 1) The pressure required for finger-jointing adhesive bonding increased with the increase of fitness ratio, especially when tenon gear angle and width of gear bottom was smaller. Finger-joint pressure increased with the increase of tenon gear length. Generally, finger-jointing pressure was proportional to the fitness ratio, and the slope decreased with the increase of tenon gear angle. 2) For all tenon types investigated in this study, the finger-jointing strength value increased with the increase of tenon gear length. The optimal finger-jointing pressure was about 8-15 MPa, which presented greater mechanical strength value. 3) The fitness ratio of maximum finger-jointing strength obtained by short tenon gear was greater than that obtained by the long tenon gear, the fitness ratio of maximum finger-jointing strength produced by 9 mm and 27 mm tenon were approximately 0.2 mm and 0.1 mm, respectively. 4) Considered from safety and economy aspects, the optimal finger-jointing parameters of L. gmelinii lamina were: angle of tenon gear 9.8°, length of tenon gear 15-20 mm, width of gear bottom 0.8-1.2 mm, finger-jointing pressure 10-15 MPa, fitness ratio 0.12-0.20 mm (the longer the tenon gear, the smaller fitness ratio used).

Key words: structural glued laminated timber (Glulam), larch, lamina, finger-joint, fitness ratio