Multi-scale characterisations of foam-formed lignocellulose materials : a cross-examination of the mechanical, morphological and functional properties

Abstract

Foam-formed lignocellulosic materials are gaining increasing attention as sustainable lightweight materials due to their low-density, porosity and renewability. This thesis reviews and explores appropriate characterisation methods for foam-formed lignocellulosic materials through previous studies and selected observations from mechanical testing. Foam-forming mechanism, fibre network structure, process parameters and relationship between micro-, meso- and macro-scale material characteristics, including mechanical, morphological and functional properties are discussed. Attention is given to the influence of fibre bonding, pore structure, density and fibre orientation on deformation behaviour, energy absorption, sound absorption and thermal behaviour. In addition, compression and tensile tests were performed on low-density foam-formed sheet samples to examine their mechanical response under selected loading conditions. The findings indicate that compression testing is useful for understanding the compressibility, deformation behaviour and energy absorption of the material, whereas tensile testing revealed limitations related to delamination and instability in tensile deformation. The results of the thesis suggest that foam-formed lignocellulosic materials have the potential for lightweight applications requiring controlled deformation and energy absorption; however, their reliable evaluation requires the combined use of mechanical, morphological and functional characterisation methods, particularly for future studies involving foam-formed sheet and three-dimensional structures.