Research On The Micro-Mechanics Model Of Wood Based The Theory Of Composite

Wood is an orthotropic natural fiber reinforced characteristics of polymer composites which is the main material in people's lives, there are many advantages unmatched by other materials, cement, steel and wood are called three construction materials, but the wood there are some natural defect, in the course prone to deformation and other problems affecting the use of wood. Studied the timber forces the relationship between the changes in the internal fine structure of the macroscopic mechanical response will increase the level of awareness on the wood failure mechanism, has a strong practical significance.First, researching a wood micro-structural features and getting the relationship between of macro-mechanical properties of wood, the object of study in wood micromechanics is cell walls because the main components of timber entity is posed by many cavity cell walls, through analysis of its flexibility constant and wood micro-structure of the relationship reflects the S2cell wall layer and the cell wall of the longitudinal elastic modulus is closely related; stiffness properties of cellulose, hemicellulose and lignin, and cell wall stiffness properties in accordance with the relevant literature, consider to the swelling properties of wood, and build the constitutive equation of the cell wall and swelling strain.This article during the timber macro, micro experiments, mainly in softwoods Larch subjects, sooner or later material distribution characteristics of the cell through a thin specimen analysis, measurement of earlywood, transition wood and latewood longitudinal elastic modulus on, and sooner or later, the thickness of the wood cell wall, the nonlinear relationship between cell stiffness distribution along the growth ring wood density, shrinkage and swelling characteristics and single-and multi-layer tensile strength testing, the establishment of the specimen density relationship with the strength of the specimen stiffness and structural changes in the relationship between the finite element modeling of the relevant data required. The figure took into account the wood curvature on the wood, and wood viscoelastic analysis, the application of a single cell modeling theory, the initial mechanical properties of macro validation.Wood micromechanics modeling by means of finite element software to the timber unit cell modeling theory as the basic unit, the unit cell finite element model constructed wood fiber reinforced unit model, build the RVE constitutive relations and boundary conditions, research fiber to enhance the interaction between body, entity simulation model of the wood fiber input, the experimental data, according to the initial model stiffness parameters to calculate the stress state to obtain the stiffness of the wood fiber, the existing wood fiber model The stiffness of an amendment to the wood fiber model stress cloud, RVE cyclical, thus available to the macroscopic stress-strain relationship of wood. Consider that the wood is a defect in materials, the timber body with defects into different area, from the micro level, consider the defect area, the different defect models into simulated in each district, with the finite element method, the establishment of a wood containing defects fiber element model, load assignment based on experimental data, the wood fiber element model of the nonlinear parameters input to the multi-layer growth ring model was validated, in order to get the stress contours in the growth ring layer, the method for solving the timber macro-mechanical properties, verify the accuracy and superiority of this choice of test methods. New wood composite material of this article will be combination of the theory of composite materials and wood micromechanics,the research is a cross-cutting-edge, timber extended use of wood range, timber utilization, R&D to be able to overcome the shortcomings, has a special tough performance and important guidance.