Wood Composite Hygrothermal Effects

This paper studied hygrothermal effects of wood-bamboo composite consisting the mechanism and rule of static bending properties, viscoelastic property. Strain of its elesment-bamboo and poplar and wood-bamboo composite itself were tested and hygro-coefficient and thermal coefficient was calculated. The relation between elements and composte was simulated by relative modle respectively. The change of dimensions, warp, and failure mode of wood-bamboo composite were simulated by Zhi, Cai warp mode.Bending properties in different moisture and temperature showed that hat modulus of elasticity and modulus of rupture of this material treated under -55℃, 4h is the best among the five hygrothermal conditions, increasing up more 130% , while that of this material treated in dring 150℃, 4h; cold water 20℃, 24h; hot water 90℃ decreased compared with that treated in 20℃, 65%. After tredated in drying and cold water, render ratio of MOE is better than render ratio of MOR, though render ration of MOE is worse than render ratio of MOR in hot water. The curve of loading and deformation veried that bamboo and wood composite plywood mainly showed low-temperature brittleness and hot brittleness when treated in cold water, frozen condition, and drying. Hot water increase the viscoelastic properties of bamboo wood composite plywood.Dynamic properties of bamboo named Phyllostachys pubescens with different moisture content and temperature changed from -130℃ ～130℃is studied by Dynamic Mechanical Thermal Analysis(hereinafter DMTA). The results show that hygrothermal effect on dynamic mechanical properties is negative. The storage modulus is down upon the temperature enhancement and moisture content increment and glass transition temperature moves to lower temperature with the moisture content increase. The glass transition temperature and tan delta of bamboo with different moisture content is repectively 10%, 30.5℃, 0.04 和 34%, 10.61℃, 0.02.Stroage modulus of poplar increased firstly, and then went down when temperature is up. In a whol, storage modulus of poplar in low moisture content is higher than that of poplar in higher moisture content. The melt temperature of poplar show hardly relative to moisture content, while toughness-britllenes transition in high temperature was decreased by moisture content increase, that is , that of poplar in 10% moisture content is more 30℃than that of poplar in 35%.The viscoelastic properties of Bamboo Laminated Veneer Lumber(hereinafter LVL) in different moisture content and temperature process tested by DMTA is similar to those of bamboo, and the same phenominon happened in poplar LVL.