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In order to reveal the influence mechanism of wood chemical composition on longitudinal static and dynamic viscoelasticity of cell wall from the perspective of micromechanics, enrich the research content of mechanical properties of wood cell wall and provide reference for selective fiber utilization, wood cell wall at 2/3 of the cross section of Pinus massoniana wood was taken as the research object. Hemicellulose and lignin in cell wall were removed step by step by chemical method, and the contents of cellulose, hemicellulose and lignin were measured by NREL’S LAPS. The changes of chemical composition of wood cell wall were analyzed by Fourier transform infrared spectroscopy. The mechanical properties such as creep compliance, storage modules and loss modulus of wood cell wall were measured by nano indentation technology. Then, the relationship between the static viscoelastic properties of wood cell wall and chemical components was studied using Burgers model. The results showed that cellulose played a leading role in the static viscoelastic properties of wood cell walls. Wood extract had little effect on the viscoelasticity of cell wall. The effects of hemicellulose and lignin on the dynamic viscoelasticity of cell wall were significant. After removing hemicellulose and lignin, the storage modulus of cell wall was reduced by 17.4% and 49.4%, respectively, while the loss modulus was increased. [ABSTRACT FROM AUTHOR]

In order to solve the problem of rutting on the cold recycled foamed asphalt pavement under the action of high temperature and heavy load, and to understand the dynamic response of the road surface when the recycled mixture was used as the lower layer and the upper base layer respectively, a high - shear and dense foamed asphalt cold recycling mixture (F - B) was designed, combined with regional climate characteristics and viscoelastic theory, obtained the temperature field of different structural layers and the strain changes under moving axle load through the finite element method, and compared with the conventional gradation. The results showed that the pavement temperature field had obvious non - linear characteristics, and the shear resistance of the material could be improved by improving the gradation. There was about 10% residual strain of the pavement after unloading, and the viscoelastic model could obtain the residual deformation of the pavement, which could better reflect the formation of ruts. The longitudinal strain of the foamed asphalt layer was alternating between positive and negative, which was easy to cause road fatigue damage. Under low speed and heavy load, the use of high shear density grading could reduce the maximum shear stress of the surface layer and the generation of flow rutting. When foamed asphalt was used as the lower layer, the road surlace had better resistance to vertical deformation under heavy load. [ABSTRACT FROM AUTHOR]