Poplar Laminated Veneer Material Creep Performance

With people's ever-growing demand for standard of living, wooden structural material will be one of the wood composite research directions in the coming several decades in China; creep behavior of materials must be studied if they are applied as structural materials. Nowadays, however, most research directions overseas of creep behavior of wood composites are concentrated on OSB (Oriental Strand Board) and fiber board; fewer researches were down on wood composites in China, even do what were down on LVL; they were concentrated on above two materials too. According to the developmental situation of wooden structure, it is very urgent for us to do quantificational research on creep behavior of LVL. After research and application of LVL were summarized, poplar LVL specimens were tested at several ways of arrangement, variant resin content, two direction of load and three stress level, and then the Burger Model was used to fit its 30-days experimental data.The result from the experiment showed that:1. At low stress level, the Burger Model can fit the experimental data fairly well. Poplar LVL shows approximately linear viscoelasticity, and there are low relative percentage errors between actual and fitted data.2. A predictive model (a semi-experience equation) is developed at low stress level for poplar LVL. Four parameters are educed, and the relationship between parameters and experimental factors was analyzed.3. The developed predicted model can predict the creep data quite well, especially in the subsequent phase. Parameters A, B and D change approximately in the same way according to different experimental conditions. Specimens have strong anti-creep prosperities when they are loaded at lateral direction. Poplar LVL exhibits Mechano-Sorptive-Effect (MSE) behavior. The variation of environmental temperature and relative humidity has influence upon specimens' creep behavior.4. After analyzing the effect that variation of stress level and adding tangential veneers to the subordinate surfaces have on parameters A, B and D, and appropriate modification being made to it, the model is applicable to a bigger extension.5. It can be approximately considered that there is only viscosity deflection 300 hours later.