scholarly journals Moisture-induced deformations of wood and shape memory

2021 ◽  
Vol 2069 (1) ◽  
pp. 012012
Author(s):  
Chi Zhang ◽  
Mingyang Chen ◽  
Dominique Derome ◽  
Jan Carmeliet
Keyword(s):  
Shape Memory ◽  
Finite Element Modelling ◽  
Atomistic Simulation ◽  
Crystalline Cellulose ◽  
Water Molecules ◽  
Cellulose Fibres ◽  
Moisture Adsorption ◽  
Reversible Deformation ◽  
Opening And Closing ◽  
Building Physics

Abstract Wood is known to swell substantially during moisture adsorption and shrink during desorption. These deformations may lead to wood damage in the form of cracking and disjoining of wooden components in e.g. floor or windows. Two swelling mechanisms may be distinguished: reversible swelling/shrinkage and moisture-induced shape memory effect. In the latter, wood is deformed in the wet state and afterward dried under maintained deformation, in order that wood retains its deformed shape even after the removal of the mechanical loading, called fixation. When wood is wetted again, it loses its fixation, partially regains its original shape, called recovery. These two mechanisms have their origin at the nanoscale and are modelled here using atomistic simulation and after upscaled to continuum level allowing finite element modelling. Hysteretic sorption and swelling are explained at nanoscale by the opening and closing of sorption sites in ad-and desorption, where in desorption water molecules preferentially remained bonded at sorption sites. The moisture-induced shape memory is explained by the moisture-induced activation of the interfaces between the reinforcing crystalline cellulose fibres and its matrix at nanoscale, referred to as a molecular switch. Our work aims to highlight that the understanding of sorption-induced reversible deformation and moisture-induced shape memory may play an important role in wood engineering and in building physics applications.

Identifying multiple forms of lateral disorder in cellulose fibres

2013 ◽  
Vol 46 (4) ◽  
pp. 972-979 ◽  
Author(s):  
L. H. Thomas ◽  
C. M. Altaner ◽  
M. C. Jarvis
Keyword(s):  
Mechanical Performance ◽  
Crystalline Lattice ◽  
Crystalline Cellulose ◽  
Multiple Forms ◽  
Cellulose Fibres ◽  
Flax Fibres ◽  
Radial Profiles ◽  
Cellulose Fibrils ◽  
Fibre Diffraction ◽  
Diffraction Patterns

Many strong biological materials exist in the form of fibres that are partially crystalline but contain a substantial proportion of disordered domains, which contribute to the mechanical performance but result in broadening of the reflections in the diffraction patterns of such materials and make structure determination difficult. Where multiple forms of disorder are simultaneously present, many of the accepted ways of modelling the influence of disorder on a fibre diffraction pattern are inapplicable. Lateral disorder in cellulose fibrils of flax fibres was characterized by a multi-step approach. First, a scattering component derived from domains less uniformly oriented than the rest was isolated. A second scattering component giving rise to asymmetry in the radial profiles of the equatorial reflections was then quantified and subtracted. This component was associated with domains that could be related to the crystalline cellulose lattice, but with more variable and, on average, wider equatorial d spacings. A further partially oriented component with highly disordered lateral d spacings unrelated to any of the cellulose lattice dimensions was identified. This component may be derived from non-cellulosic polysaccharides. The remaining broadening was then separated into a contribution from disorder within the crystalline lattice, including known disorder in hydrogen bonding, and a Scherrer contribution from the microfibril diameter. The methods described are likely to find applications in the study of both natural and synthetic polymer fibres in which mechanical properties are influenced by disorder.

Atomistic Simulation of Nafion Membrane. 2. Dynamics of Water Molecules and Hydronium Ions

2007 ◽  
Vol 111 (45) ◽  
pp. 13006-13013 ◽  
Author(s):  
R. Devanathan ◽  
A. Venkatnathan ◽  
M. Dupuis
Keyword(s):  
Atomistic Simulation ◽  
Nafion Membrane ◽  
Water Molecules ◽  
Hydronium Ions

scholarly journals Магнитокалорический эффект и эффект памяти формы в сплаве Гейслера Mn-=SUB=-2-=/SUB=-NiGa

2020 ◽  
Vol 62 (5) ◽  
pp. 726
Author(s):  
А.П. Каманцев ◽  
Ю.С. Кошкидько ◽  
Э.O. Быков ◽  
В.С. Калашников ◽  
А.В. Кошелев ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Shape Memory ◽  
Mechanical Stress ◽  
Magnetocaloric Effect ◽  
Wide Temperature Range ◽  
Electrical Resistance ◽  
Heusler Alloy ◽  
Experimental Methods ◽  
Reversible Deformation ◽  
Arc Melting

The work presents the investigations of the functional properties of the Heusler alloy Mn2NiGa, made by argon arc melting. The direct experimental methods were used to study: electrical resistance, magnetization, magnetocaloric effect, and shape memory effect in the wide temperature range of 100–400 K. The inverse magnetocaloric effect was found in both the martensitic and austenitic phases, which did not experience saturation in pulsed magnetic field up to 50 T. The values of reversible deformation in the alloy up to 0.35% were obtained with bending mechanical stress up to 247 MPa.

scholarly journals The effect of the natural degradation process on the cellulose structure of Moroccan hardwood fiber: a survey on spectroscopy and structural properties

2019 ◽  
Vol 8 (3) ◽  
pp. 179 ◽  
Author(s):  
Abdellatif Boukir ◽  
Ikram Mehyaoui ◽  
Somia Fellak ◽  
Laurence Asia ◽  
Pierre Doumenq
Keyword(s):  
Raman Spectroscopy ◽  
Crystallinity Index ◽  
Crystalline Cellulose ◽  
Cellulose Fibres ◽  
Amorphous Cellulose ◽  
Cellulose Structure ◽  
Ft Raman Spectroscopy ◽  
Long Time ◽  
Natural Degradation ◽  
Ft Raman

<p>The aim of this work is to study the effect of natural degradation on the cellulose structure conformation changes of 2 ageing Moroccan hardwoods (400 and 500 years) compared to recent one considered as a reference; and to provide information on the polymorphs content variability from two-phases material (crystalline and amorphous) influenced by a long time of ageing and environmental degradation effects. In order to investigate the effects of both natural degradation conditions and a long time of exposure on cellulose structure conformation (examined samples) with estimating their content (crystalline and amorphous cellulose), three combined techniques XRD, ATR-FTIR and FT-Raman spectroscopy were used. XRD results associated with the crystallographic planes and Miller indices provide information on the presence of a mixture of celluloses polymorphs (crystalline cellulose I, II, I<sub>b</sub> and amorphous phase). The decrease in crystallinity-index values from recent to aged ones (38 to 19.5%) confirms well the occurred alteration of crystalline cellulose fibres and their evolution towards a high content of the amorphous form. The prominent regression in the intensities of three FTIR fingerprint cellulose regions evolving towards an overall increase in the intensities of C=O area (1733-1630 cm<sup>-1</sup>) is a sign on the introduced changes on cellulose conformation and cellulose fibres degradation more accentuated in the case of the very aged sample (500 years). Similar results were confirmed by combining FT-Raman spectroscopy as a vibrational technique. No work has been done on this genus of degraded Moroccan hardwood and the relevance of this study is to investigate the compositional content and structural conformation, to determine the variability in the forms of both crystalline and amorphous cellulose phases with estimating the evolution of their polymorphism, and to monitor the degree of crystalline cellulose fibres deterioration.</p>

scholarly journals The effect of the natural degradation process on the cellulose structure of Moroccan hardwood fiber: a survey on spectroscopy and structural properties

2019 ◽  
Vol 8 (3) ◽  
pp. 179-190 ◽  
Author(s):  
Abdellatif Boukir ◽  
Ikram Mehyaoui ◽  
Somia Fellak ◽  
Laurence Asia ◽  
Pierre Doumenq
Keyword(s):  
Raman Spectroscopy ◽  
Crystallinity Index ◽  
Crystalline Cellulose ◽  
Cellulose Fibres ◽  
Amorphous Cellulose ◽  
Cellulose Structure ◽  
Ft Raman Spectroscopy ◽  
Long Time ◽  
Natural Degradation ◽  
Ft Raman

The aim of this work is to study the effect of natural degradation on the cellulose structure conformation changes of 2 ageing Moroccan hardwoods (400 and 500 years) compared to recent one considered as a reference; and to provide information on the polymorphs content variability from two-phases material (crystalline and amorphous) influenced by a long time of ageing and environmental degradation effects. In order to investigate the effects of both natural degradation conditions and a long time of exposure on cellulose structure conformation (examined samples) with estimating their content (crystalline and amorphous cellulose), three combined techniques XRD, ATR-FTIR and FT-Raman spectroscopy were used. XRD results associated with the crystallographic planes and Miller indices provide information on the presence of a mixture of celluloses polymorphs (crystalline cellulose I, II, Ib and amorphous phase). The decrease in crystallinity-index values from recent to aged ones (38 to 19.5%) confirms well the occurred alteration of crystalline cellulose fibres and their evolution towards a high content of the amorphous form. The prominent regression in the intensities of three FTIR fingerprint cellulose regions evolving towards an overall increase in the intensities of C=O area (1733-1630 cm-1) is a sign on the introduced changes on cellulose conformation and cellulose fibres degradation more accentuated in the case of the very aged sample (500 years). Similar results were confirmed by combining FT-Raman spectroscopy as a vibrational technique. No work has been done on this genus of degraded Moroccan hardwood and the relevance of this study is to investigate the compositional content and structural conformation, to determine the variability in the forms of both crystalline and amorphous cellulose phases with estimating the evolution of their polymorphism, and to monitor the degree of crystalline cellulose fibres deterioration.

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