Modeling the mechanical properties of Pinus Radiata
Thesis DisciplineMechanical Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
The study of a methodology to model the mechanical properties of Pinus Radiata takes place from the nanoscopic cell fiber  to the board scale level. Gibson and Ashy had generalized wood cells into hexagonal cells, previous work  extends the model specifically for Pinus Radiata. Unfortunately, earlier work was done on published data from various sources, not necessary related to Pinus Radiata nor from a common reference piece of characterized Pinus Radiata, making correlation with experimental work  difficult. Further work was done by the author on a characterized sample of Pinus Radiata to correlate elastic properties with actual cellular geometry and experimental result. Critical geometrical parameters were studied for a feasible mathematical idealization as necessary parameters to further refine the FEM model. Two approaches were used in evaluating board scale modeling; actual wood cells geometry and idealized hexagonal models. These models are extended to Growth ring model to predict growth ring mechanical properties and validated with experimental results as a preliminary Board scale model. Stol had modeled Wood cells as hexagonal cellular material using Gibson's  analytical solution in his work with orthotropic wood wall's properties . Sto1's analytical solution neglects the longitudinal dimension, which in realism is closer to plate than beam. Gibson and Asbhy's work on prediction of cellular properties analytically formed the basis of formulation analytical solution using energy method (Ritz's method) with plate type stiffness function and further extended with shear and longitudinal boundary coupling effect. The plate analytical solution was validated by FEM to be in close agreement, within a 5% error. The model based on real cell geometry and its equivalent regular array of identical cell has broad agreements with experimental values. Further refinements of this model are important steps in the development of a definitive model. Preliminary work on a growth ring FEM model is important as part of the preparation for a board scale model, however further refinements would be necessary for definitive board scale FEM model.