Recent progress in the study of the rheology of wood

Schniewind, Arno P.

doi:10.1007/bf00350908

Cited by 35 publications

(4 citation statements)

References 35 publications

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“…Firstly, water could transport due to cell wall sorption and diffusion of bond water in the cell wall even when diffusion in the porous system does not occur. Secondly, sorption causes stress relaxation in cell walls [60,61], and stress relaxation could increase the sorption capacity of the cell wall [58]. The synergistic relationship between water sorption and stress relaxation in the cell walls is likely to increase the total diffusion rate in the long-term.…”

Section: Effect Of Moisture On Interlaminar Shear Properties Of Bcmentioning

confidence: 99%

Interlaminar Shear Properties of Bamboo Composite for Structural Applications

Rajabipour

Javadian

Bazli

et al. 2022

Fibers

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Interlaminar shear strength in bamboo composite (BC) is mainly provided by epoxy resin as the matrix in BC. This may greatly change due to humidity. This study aims at evaluating the shear strength of BC by testing and developing probabilistic relationships. The interlaminar shear strength of bamboo composite (BC) in different moisture conditions was tested according to ASTM D2344. The results show that the maximum shear stress does not generally occur at the centroid of samples, which could be associated with imperfections in BC layers. An extreme value theory-based model is suggested to evaluate the probability of shear failure in BC samples. The shear capacity decreased from 20.4 MPa to 14 MPa as the humidity increased from 60% to 90%. A summary of findings is as follows: It was found that under transient moisture conditions, local failure is likely to happen before the first significant crack occurs. Local failure is suggested to be considered in the design for serviceability. Stress drop caused by the local failure could exceed 10% of total shear strength and, therefore, should be regarded as a serviceability design. The probabilistic model developed in this study could be used for developing structural design safety factors.

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Section: Effect Of Moisture On Interlaminar Shear Properties Of Bcmentioning

confidence: 99%

Interlaminar Shear Properties of Bamboo Composite for Structural Applications

Rajabipour

Javadian

Bazli

et al. 2022

Fibers

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“…Despite its importance, research on the mechano-sorptive creep of CLT remains limited. In the early stage of research, the evaluation of creep behaviour in wood materials was primarily conducted through experiments utilizing both small clear wood specimens and full-scale timber products [4][5]. These wood materials were analysed by utilizing rheological and viscoelastic theories, leading to a thorough understanding of their creep behaviour.…”

Section: Introduction 123mentioning

confidence: 99%

Effects of Panel Direction, Load Level and Ambient Humidity on the Creep of Downscaled Cross-Laminated Timber

Wang

Chen

Gong

et al. 2023

World Conference on Timber Engineering (WCTE 2023)

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The creep behaviour of wood or engineered wood products is an important factor in the consideration of the serviceability of a timber structure. This study evaluated the effect of creep of downscaled cross-laminated timber (CLT) specimens by considering panel direction, load level and relative humidity (RH). The test materials were sprucepine-fir (SPF) lumber and polyurethane adhesive. Static bending, one-week creep and four-month creep tests were conducted. It was found that: 1) CLT specimens had an average proportional limit (PL) of around 3,024 N and 817 N in the "Major-strength" and "Minor-strength" directions, respectively; 2) Panel direction strongly impacted time-dependent deflection, with the "Minor-strength" specimens exhibiting a 2 to 2.5 times as large deflection as the "Major-strength" ones; 3) Load level clearly affected the load-deflection behaviour due to the layup of the specimens; 4) Ambient humidity had a little effect on 7-day creep, but impacted the 4-month mechano-sorptive creep to some degree; and 5) The "Generalized Kelvin" model seemed to be suitable in simulation the creep of the downscaled CLT specimens used in this study. The upper limit of the model at 95% confidence level could be a good approach to simulate the creep of the specimens under cyclic RH.

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“…Free methoxyl and free phenolic hydroxyl groups hinder crosslinking and lower the glass transition temperature, thus increasing the flexibility of the structure. Lignin is known to have a low ability to sorb water compared to the hydrophilic hemicelluloses and cellulose, and high lignin content in wood results in lower overall water sorption capacity (Schniewind and Berndt 1991). In addition, the shrinking and swelling behaviour of wood is related to its hygroscopicity and water sorption ability, and therefore lignin is considered to improve the dimensional stability of wood.…”

Section: Introductionmentioning

confidence: 99%

“…Lignin is regarded as being associated or linked by covalent bonds to some hemicelluloses (Fengel and Wegener 1984). It is also well established that hemicelluloses are distributed through the lignin network, which strongly indicates that hemicelluloses form a link between cellulose framework and lignin matrix in the cell wall structure (Schniewind and Berndt 1991). The complex network structure of lignin, together with the strong association with hemicelluloses, restricts the exploitation of lignin as a valueadded chemical, due to the lack of effective isolation methods in which the polymeric structure and its activity are maintained.…”

Section: Introductionmentioning

confidence: 99%

Method to prepare smooth and even cellulose-lignophenol films

Tammelin

Harlin

Vehviläinen

et al. 2011

BioRes

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Dissolved cellulose was contacted with dissolved linear or slightly branched lignophenol polymers in alkaline solution, and films were formed through precipitation. Lignophenol is a polymeric lignin derivative isolated from wood meal, and due to its size and chemical structure, it is expected to a better model for natural lignin compared to the previously exploited small lignin model molecules. Smooth and even of cellulose-lignophenol films were achieved, and the interactions between cellulose and lignophenol were tentatively detected. The formed film structures had the crystalline form of cellulose II, and they did not contain any fibril-like material. Although the amount of hemicelluloses was negligible, it seems that the lignin modelling lignophenol tended to positively interact with cellulose.

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Recent progress in the study of the rheology of wood

Cited by 35 publications

References 35 publications

Interlaminar Shear Properties of Bamboo Composite for Structural Applications

Interlaminar Shear Properties of Bamboo Composite for Structural Applications

Effects of Panel Direction, Load Level and Ambient Humidity on the Creep of Downscaled Cross-Laminated Timber

Method to prepare smooth and even cellulose-lignophenol films

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