Study On Manufacturing Technology Of Larch Engineering Glued Laminated Timber

Larch is an important commercial forest timber resource in our country. In this paper, Dahurian Larch was studied. Through carried out the study of contrasting gluing performance of different structural adhesive, the influence law of different factors affect the gluing performance of Larch glulam, the influence law of finger parameters on finger joint strength of Larch glulam. We obtained the key technologies of the manufacturing process of Dahurian Larch glulam, and provide the reference and basis for industrial production for Larch and other wood species engineering glulam.The research results showed as follows:1. Only the shearing strength of two-component polyurethane didn’t reached the national standard Technical code of glued laminated timber structures (GB/T 50708-2012) in the four adhesives. The shearing strength of resorcinol-formaldehyde resin and polyvinyl acetate-isocyanate reached the shearing strength of PF. For manufacturing the Larch glulam, the shearing strength of one-component polyurethane, two-component polyurethane and polyvinyl acetate-isocyanate reached the national standard Structural glued laminated timber (GB/T 26899-2011), two-component polyurethane and polyvinyl acetate-isocyanate exceed the strength of Larch timber and. In the aspects of stripping resistance, polyvinyl acetate-isocyanate was best, two-component polyurethane took second place, one-component polyurethane was the worse. While the strength of adhesive is lower than the strength of wood, wood failure ratio and the shearing strength of the specimens have more obvious positive correlation.2. The existence of knots on the glued surfaces influenced the gluing performance of timber. The shearing strength of knot-knot samples didn’t entirely reached the national standard Structural glued laminated timber (GB/T 26899-2011). The dimensions of knots have significant impact on the gluing property of timber, the gluing property of timber decreased with increment of the area of knots on the glued surfaces. Bonding pressure, exposure time, roughness and the texture of bonding surface has a certain influence on shear properties and peel resistance of glulam. Exposure time and bonding pressure have a relatively large influence on the shear performance, the bonding pressure and the texture of bonding surface have a relatively large influence on the peel resistance. Comprehensive consideration, the optimum technological parameters for dahurian Larch glulam manufacturing were as follows:remove the knots that the diameter of the knots more than 20 mm, bonding pressure 0.9 MPa, direct agglutination after planning.3. The fitness ratio evidently affected the value of the end pressure. The biggest end pressure increased with the increase of the fitness ratio in the same tenon-type. The influence law of the tenon-type to the value of the end pressure was also significantly, the longer length of the tenon, the greater value of the end pressure in the same fitness ratio. But, the greater fitness ratio and the longer length of the tenon, the roots of the tenon were more prone to splitting phenomenon. With the increase of fitness ratio, the bending strength and tensile strength increased at first then decreased in the same tenon-type. The best fitness ratio of the different tenon-type was as follows:0.3mm,0.3mm,0.2mm, 0.1mm,0.1mm. With the increase of the length of the tenon, bending and tensile properties of the specimens were improved. Within the scope of this test, the best parameters of finger joint were as follows:tenon-type III with the fitness ratio 0.2mm, the pressure value was 13.7 MPa.