Numerical Analyses of Micro Hygro-Mechanical Behaviours of Wood Fibre Reinforced Composites

Name: Nuttibase Charupeng

LCSH: Kasetsart University -- Dissertations. D.Eng. (Mechanical Engineering) 2021

Classification :.LCCS: TA418.9.C6

LCSH: Kasetsart University. -- Department of Mechanical Engineering -- Dissertations

LCSH: Fibrous composites

LCSH: Polymeric composites

LCSH: Fiber reinforced plastics

LCSH: Numerical analysis

LCSH: Finite element method

Abstract: Wood fibre reinforced composites have become increasingly attractive in building materials industries since wood fibres are low-cost biodegradable materials that offer good specific properties. However, moisture-induced swelling, or hygroexpansion, deteriorate the long-term durability of wood fibre-polymer composites (WPC). It is also extremely difficult to experimentally determine the elastic properties of single wood fibres due to the structural complexity and variability of basic properties. Furthermore, laboratory experimentation usually takes a great deal of time, from weeks to months, to completely obtain the diffusion kinetics as the process. This has led to several ongoing theoretical and numerical studies for hygro-mechanical behaviours of WPC. In this thesis, a modelling algorithm for predicting the elastic constants of a single wood fibre is written. The model bases on finite element method (FEM) to perform calculations in three consecutive length scales of fibres including nanostructure of cellulose microfibrils (25-30 nm), ultrastructure in the fibre wall layers (2-3 um), and single wood fibres (30-40 um). The results for a given set of parameters are compared to previous studies with good agreement. The work exhibits its novelty through the model's robustness and potential for industrial applications. It merely requires three essential inputs - chemical composition and bulk density of fibre and microfibril angle of $S_2$ wall layer, but is capable of predicting reasonably accurately the elastic constants of a wood fibre completely without any required model preprocessing or meshing like common commercial FEM software packages. Furthermore, the validated model is used to perform a parametric study. We have found that cellulose content has positive correlations with almost all the elastic parameters - relatively strong for EA, ET and GT, but weaker for vT. Lignin and hemicellulose have the greatest influence on GA and vA. The bulk density of fibre is shown to affect all elastic constants except the longitudinal elastic modulus. To simulate the diffusion kinetics and the consequential hygroexpansion subjected to moisture absorption, a space-time finite element algorithm with time discontinuous Galerkin (TDG) method is developed. The above validated algorithm is employed to determine the elastic constants of wood fibres of WPC. The formulation of matrix equations in spatial and temporal domains are explained in.

Kasetsart University. Office of the University Library

Address: Bangkok

Email: tdckulib@ku.ac.th

Name: Prapot Kunthong

Role: Thesis Advisor

Name: Prapot Kunthong

Role: Thesis CO-Advisor

Created: 2021

Modified: 2025-07-25

Issued: 2025-07-25

วิทยานิพนธ์/Thesis

application/pdf

URL: https://www.lib.ku.ac.th/KUthesis/2564/nuttibase-cha-all.pdf

CallNumber: TA418.9.C6 .N88

eng

DegreeName: Doctor of Engineering

Level: Doctoral Degraee

Descipline: Mechanical Engineering

Grantor: Kasetsart University

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