Finite Element Modelling Of Microstructure Of Wood And Simulate Its Property Of Mechanics And Heat

Wood material is requisite for human living and production. Throughout human history, it is unquestionable wood material has the close relationship with human and has the most harmonious development with environment. Once wood was the main source of energy for human,and wood is a renewable energy source, hence wood material research is always a focal point to human. The appearance of the finite element method would provide human a new way to research wood. We Can approximate the true situation long as the division is exact and units are small enough.Computer technology has provided human an powerful calculation objective, and also provided human the visual analysis results of the practical application utilize finite soft which has powerful preprocessor and postprocessor. And then the finite element method become a popular numerical method with the combination of the solid theory, implement modularity, operation digitization and the strong applicability.In this paper, the mechanical and heat properties of wood microstructure were studied systematically with a great deal of tests based on the former researches in the field. During the modeling of wood mechanical properties, material microstructure computation, FEM and heterogeneous theory were applied. The average performance of wood fiber with the other organizations was considered synthetically whose geometric and material information were integrated into an equivalent body.The average property of complex periodic-microstructure material was substituted by the equivalent uniform continuum.The relative equations between micro vector fields and macro ones were established through the boundary conditions of stress and displacement in the basic units where the field of strain and stress was obtained by known macro vector fields,geometric and physical equations.Finally,constitutive equation that is the relation between macro stress and strain of special units was achieved according to heterogeneous theory with C3D8 adopted as a model to calculate the efficient performance in the simulation software of ABAQUS.In the macro-scale, wood is a anisotropic, multiaperture and capillary colloid. And in the micro-scale, wood is considered as a composite material with fiber reinforcement cell wall layers. In chemical point, wood consist of cellulose, hemicellulose and lignin. The article gives the character of stiffness matrix, regard as elastic constants of cell wall when simulation. With the use of the developed hierarchical model, the influence of the microstructure, including microfibril angles (MFAs), the shape of the cell cross-section and the cell dimension, moisture content, on the elastic properties of softwood was studied. Last we provide the wood heat transfer properties. The above results fit on the theoretical values and experimental values. It give a proof that the model is applicative.In this study, finite element theory, homogenization theory, composite material theory and wood micro-mechanics are researched which are of cross-frontier research to improve the awareness on the mechanical properties of wood from micro to macro,expend the scope of application,enhance the wood utilization level.The investigation is of great significance for sustainable development of wood industry.