Study On The Interface Bond Behaviour Of Preservative-treated Glued Laminated Timber

Using preservative-treated dimension lumber to produce glued laminated timber is an effective technical measure to solve the poor anti-corrosion of glulam.After the lumber is treated with preservatives,the interface bond behaviour is the key to the production of preservative-treated glued laminted timber.The interface layer of SPF preservative-treated glulam and European red pine preservative-treated glulam is taken as the research object.The wettability and cohesiveness of the surface of the anti-corrosion glue laminated timber,the bond behaviour,fracture toughness and durability of the interlayer interface of the anti-corrosion glued wood laminates were systematically studied.The principal results are as follows:1)basic properties of preservative-treated glued laminated timber surfaceIn order to evaluate the wettability,cohesiveness and morphological characteristics of the surface of the preservative-treated glued laminated timber,the wettability and cohesiveness of the surface of the glued wood laminate with different tree species and different cutting degree were studied by means of the small drop contact angle test and the local surface bonding pull-out test.And the atomic force microscope(AFM)was used Microscopy(AFM)was used to characterize the surface structure of anti-corrosion plywood.The results showed that: because some components,such as bivalent copper and propiconazole,attached to wood fiber and occupied part of the wood space,the preservative had a significant effect on the wettability and cohesiveness of the surface of the anti-corrosion plywood;the preservative treatment had a significant difference on the wettability of the surface of Pinus koraiensis and SPF wood,and the anti-corrosion plywood of Pinus koraiensis was more significant;planing can effectively improve the wettability and cohesiveness of the laminate surface,and the increase of the number of planing can gradually reduce the increase of the wettability of the laminate surface;The adhesive property of SPF wood surface is slightly higher than that of Pinus densiflora;AFM imaging results in the air can clearly reveal the nano structure of the surface of the anti-corrosion plywood before and after cutting,and the preservative nano particles gathered on the surface after cutting are relatively evenly distributed on the wood surface,with a relatively small proportion.2)interfacial shear properties of preservative-treated glued laminated timberIn order to evaluate the interfacial shear properties of the preservative-treated glued laminated timber,the block shear test method was used to study the interfacial shear properties of the preservative-treated glued laminated timber with different species,types of adhesives,cutting degree,humid and hot environment and natural aging treatment.The results showed that the preservatives accumulated on the surface of the laminate had a great influence on the bonding performance of the preservative-treated glued laminated timber,and the interfacial shear strength of SPF and Pinus koraiensis was significantly lower than that before the preservative-treated treatment;the interfacial shear performance of the preservative-treated glued laminated timber could be effectively improved by planing the surface of the preservative-treated glued laminated timber;in the preservative-treated group,the bonding performance of resorcinol adhesive was significantly better than that of the one component polyurethane adhesive.It showed that resorcinol adhesive was more suitable for the composite of preservative-treated glued laminated timber.In the glued wood without preservative treatment,the adhesive properties of the two types of adhesives have little difference;with the increase of environmental humidity,the shear strength of the interlayer interface of the preservative-treated glued laminated timber is reduced;in the high humidity environment,the shear strength of the interlayer interface of the preservative-treated glued laminated timber is slightly higher than that of the glued wood without preservative treatment.The influence of one component polyurethane glue and resorcinol glue on the interlaminar shear strength in high humidity environment was little different;under the same conditions,the interlaminar shear strength of SPF preservative-treated glued laminated timber was slightly higher than that of Pinus densiflora preservative-treated glued laminated timber;with the increase of natural aging cycle.The interfacial shear strength of SPF preservative-treated glued laminated timber decreased with polynomial function3)interface fracture toughness of preservative-treated glued laminated timberIn order to evaluate the fracture toughness of the interface between the layers of the preservative-treated glued laminated timber,the double cantilever beam test method and the end cut three point bending test method were used to study the type I and type II fracture toughness of the preservative-treated glued laminated timber with different tree species,glue species and plane cutting,and the high-speed non-contact optical three-dimensional deformation measurement method was used to analyze the fracture process of the interface between the layers of the preservative-treated glued laminated timber.The results showed that the fracture toughness of type I and type II of interlayer interface of SPF and red pine preservative-treated glued laminated timber was significantly lower than that of untreated Glulam.The preservatives accumulated on the surface of the laminate will affect the bonding performance of the interlayer interface of the preservative-treated glued laminated timber,thus significantly reducing the type I and type II fracture toughness;the surface ivlanning treatment of the laminate can significantly improve the type I fracture toughness of the interlayer interface of the SPF preservative-treated glued laminated timber,but not the type I fracture toughness of the interlayer interface of the Pinus koraiensis preservative-treated glued laminated timber;the surface ivlanning treatment of the laminate can improve the SPF and Pinus koraiensis koraiensis Type II fracture toughness of the interlayer interface of the preservative-treated glued laminated timber;the type of adhesive has a great influence on the fracture toughness of the interlayer interface of the preservative-treated glued laminated timber,and the fracture toughness of type I and type II resorcinol adhesives were better than that of single component polyurethane adhesives;the type of adhesive had a little influence on the fracture toughness of the interface after the cutting of the preservative-treated glued laminated timber,and the fracture toughness of type I and type II resorcinol adhesives is slightly better It is superior to the single component polyurethane adhesive.The method of image strain test can directly analyze the stress-strain distribution changes in each stage of the I-type and II type fracture process of the preservative-treated glued laminated timber interlayer.The two fracture types showed the same rule.After the prefabricated crack reached the crack load,the crack expand rapidly,and the stress singularity at the crack tip extends along the near plane of the interlayer thin interface layer,The stress at the crack tip changed from strong to weak.