Research On The Multi-effective Laminated Reinforcement Of China's Plantation Wood-structural Engineering Materials

Plantation area in China has reached 8 million mu.The processing technology is backward with low technology resulting in the plantation wood in the long state of low-effective application.In recent years,with the rapid development of China's economic,the rise of national incomes and the gradual improvement of people's living standards,wooden bridges,and ancient building maintenance,flood prevention and relief,earthquake relief,subway,tunnel,etc.,require a lot of the wood-structural engineering materials.So the wood-structural engineering material is the important way of high-efficient processing and application of artificial fast-growing wood.However,the low strength of plantation wood causes a big barrier for carrying load,and the plantation wood is easy to decay and burn,especially in harsh outdoor conditions,it would accelerated aging,cracking and deformation etc.,reducing and even losing its use value,which could serious damage the safety and service life of engineering.Only few research achievements are about multi-effectively modification and laminated reinforcement of China's plantation wood.It is difficult to simultaneously overcome the defects of plantation wood such as low strength,easy decay and burn,etc.,which cannot provide strong technical support to improve the wood-structural engineering materials processing.Therefore,in order to solve the above-mentioned problems,the plantation wood(including bamboo)is served as the research object to research on the characteristics of veneer gluing and selecting of tree species for structural engineering materials,the integrating modification of plantation wood with anti-corrosion,anti-flaming and reinforcement and the processing of laminated gluing,the composite method of multi-materials laminated reinforcement,and the finite element modeling analysis of composited reinforcement mode and the stress fracture form,which ultimately to solve Chin's plantation wood applied in the manufacture of the wood-structural engineering materials to provide a scientific basis.(1)The typical China's plantation wood such as eucalyptus veneer,poplar veneer and bamboo mat are served as the research objects and the full-factor experiment method are applied to explore the characteristics of veneer gluing to select tree species for structural engineering materials.The results show that the bonding strength gradually reduces with the thickness increase of eucalyptus veneer,bamboo mat and poplar veneer,the bond strength significantly increases with the impregnation of phenolic resin,and the poplar veneer and eucalyptus veneer impregnated with phenolic resin is suitable for the manufacturing of structural engineering materials while the bamboo mat is not suitable for the manufacturing of structural engineering materials.(2)Specific modification method is carried to deal with plantation wood aiming at anti-corrosion,anti-flaming and reinforcement and the processing of laminated gluing are explored.The results show that the amount of preservatives and flame retardants of has the most significant effect on the bonding strength of eucalyptus veneer,the impregnation time of phenolic resin adhesive has more significant effect on the bonding strength of eucalyptus veneer and the hot-press time has the most significant effect on the bonding strength and modulus of elasticity of laminated lumber while little effect on modulus of rupture.Furthermore,the processing parameters of eucalyptus veneer applied for the manufacturing of structural engineering materials are confirmed with the hot-press time of 1.6 min/mm,the hot-press pressure of 3.0Mpa and the preload thickness of 30mm.Besides,the processing parameters of eucalyptus veneer modification with anti-corrosion,anti-flaming and reinforcement are confirmed with the preservatives amount of 30ml/40×40cm,the flame retardant amount of 1.0g/40x40cm and the impregnation time of 18h.(3)The basic mechanical properties experiment of Glass fiber cloth(GFRP)reinforcing laminated veneer lumber is carried to meet with the basic requirements of wood-structural engineering materials.The test results show that glass fiber reinforcing material arranged in laminated veneer lumber has negative effect on the internal bonding strength,the bonding strength nearly linear decreases with the arrangement pattern of GFRP,the GFRP reinforcing ratio and arrangement pattern have significant effect on modulus of rupture while nearly no effect on modulus of elasticity,and a mathematical model of static bending strength for LVL reinforced with GFRP is proposed,which can consider the influence of reinforcing ratio and arrangement pattern of GFRP.(4)The basic mechanical properties experiment of reinforced laminated veneer lumber with the reinforcing materials of glass fiber cloth,aluminium foil and copper foil is carried to meet with the basic requirements of wood-structural engineering materials to explore the effect of the multi-materials on the mechanical properties of LVL.The results show that the influence of reinforcing material type on modulus of rupture and standard modulus of elasticity is significant and the influence of reinforcing material layer number and assemble pattern on standard MOR and MOE is more significant than on MOR and standard MOE,and the glass fiber cloth combined with the aluminum foil as the reinforcing materials and the aluminum foil placed on the outermost surface of glued laminated timber is the best assemble pattern to make the glued laminated timber,and the limit load and safety factor of the glued laminated timber can be increased by the thickness of veneers and the parallel assemble structure of veneers is superior to its cross assemble structure.(5)The basic mechanical properties experiment and the finite element modeling of reinforced laminated veneer lumber with the reinforcing materials of glass fiber cloth,aluminium foil is carried to explore the composited reinforcement mode and stress fracture form.The results show that the reinforced effect is not obvious reinforced with glass fiber cloth,aluminium foil under parallel loading,while the composited method has better reinforced effect than single method under vertical loading.What's more,the fracture mode was the sliding type at first and followed by the tearing type under vertical loading,while the only open fracture under parallel loading.And the fracture mode has no relationship with the reinforcing materials under parallel loading and it's reasonable for wood structure to support load under vertical loading.Besides,the simulation results are consistent with the test results.