The Research On Viscoelastic Variation Of Rheological Aging Of Resin Reinforced Bioboard

Taking the basic theory of rheology as the starting point,this paper closely combined with the Hunan province science and technology leading talent project:"Wood Science and Technology"(No.2016RS2011),using the fast-growing willow as the raw material of the resin reinforced bioboard of the research object,the hydrothermal aging test of resin reinforced bioboard under different aged time was carried out by using programme-controlled temperature and humidity chamber and combining the macroscopic and microstructure changes of the material.The influence of hydrothermal aging on the bending properties of resin reinforced bioboard was studied.On this basis,the bending creep behavior of resin reinforced bioboard under different aged time and stress levels was studied.The main works and creative achievements are as follows:(1)The influence of hydrothermal aging on the macroscopic and microstructure of resin reinforced bioboard were studied.The apparent color of the material was gradually deepened with the increase of aged time was observed.Meanwhile,the microstructure photos of the untreated and experienced hydrothermal aging treatment five cycles on the resin reinforced bioboard were observed by using scanning electron microscopy(SEM)at different magnification times,which indicated that hydrothermal aging had a certain influence on the structure of the lengthwise section of it,and the alternation of temperature and moisture content caused the bonding strength of the resin reinforced bioboard to decrease,thus reduced the durability of the material.(2)The bending creep tests of rein reinforced bioboard under different aged time(Oh,24h,48h,72h,96h and 120h)were carried out under different stress levels(69.2MPa,86.5MPa,103.8MPa)through the electronic universal testing machine.According to industry practice,the above stress levels were obtained by 40%?60%of bending strength of unaged treatment samples.The test results showed that the stress level and the length of the hydrothermal aging time had certain influence on the creep properties of resin reinforced bioboard.Under the same aged condition,the creep rate of the resin reinforced bioboard increased with the increase of the applied constant stress level.Under the same stress level,the creep compliance of resin reinforced bioboard increased with the increase of aged times.(3)According to the time-stress equivalent principle,the main creep curves of resin reinforced bioboard under different aged times were constructed at reference stress levels(? = 69.2MPa).In addition,the Burgers rheological model was adopted to fit and analyze the creep compliance main curve of the resin reinforced bioboard which under different aged time at the reference stress level(? = 69.2MPa),and the corresponding model parameters were obtained.The fitted results showed that the Burgers rheological model had a strong capability of describing the viscoelastic variation of the resin reinforced bioboard under different aged times.(4)According to the time-aging time equivalent principle,the main creep curves of resin reinforced bioboard under each stress level were constructed at reference aging time(48h).Moreover,through the horizontal shift,the creep compliance master curve under different stress levels were improved by 2.7?4.9 orders of magnitude on the logarithmic time axis.In addition,the Burgers rheological model was adopted to fit and analyze the creep compliance main curve of the resin reinforced bioboard under each stress level at reference aging time(48h),and the corresponding model parameters were obtained.The results showed that the Burgers rheological model can describe well the viscoelastic creep properties of the resin reinforced bioboard which under different stress level.