Influence of variation in modulus of elasticity on creep of wood during changing process of moisture

Takahashi, Chika; Nakazawa, Noriko; Ishibashi, Kazuyuki; Iida, Ikuho; Furuta, Yuzo; Ishimaru, Yutaka

doi:10.1515/hf.2006.070

Cited by 17 publications

(9 citation statements)

References 15 publications

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“…The similar phenomena were also reported when wood was subjected to bending force by Takahashi et al [35], Lu et al [36], and Jiang et al [37]. When water molecules penetrated into the wood cell wall, a slight amount of water induced a bridge effect involving hydrogen bonds forming a relative ordered cohesion state between molecular chains [35]. In the previous studies [14,30,32,38], the moisture ranges were limited, in hence, no local maximum value of E L were reported.…”

Section: Tensile Modulus Esupporting

confidence: 87%

“…The local maximum value of E L was 10.7, and 8.4 GPa, respectively for poplar at 2.0% MC and Chinese fir at 2.4% MC. The similar phenomena were also reported when wood was subjected to bending force by Takahashi et al [35], Lu et al [36], and Jiang et al [37]. When water molecules penetrated into the wood cell wall, a slight amount of water induced a bridge effect involving hydrogen bonds forming a relative ordered cohesion state between molecular chains [35].…”

Section: Tensile Modulus Esupporting

confidence: 78%

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Orthotropic Tension Behavior of Two Typical Chinese Plantation Woods at Wide Relative Humidity Range

Kuai

Wang

et al. 2019

Forests

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Research Highlights: Orthotropic tension behaviors of poplar and Chinese fir were investigated at a wide relative humidity (RH) range. Background and Objectives: Poplar and Chinese fir are typical plantation tree species in China. Mechanical properties of plantation-grown wood varies from naturally-grown one. To utilize poplar and Chinese fir woods efficiently, fully understanding their moisture content (MC) and orthotropic dependency on tension abilities is necessary. Materials and Methods: Plantation poplar and Chinese fir wood specimens were prepared and conditioned in series RH levels (0–100%). Tensile modulus (E) and strength (σ) were tested in longitudinal (L), radial (R), and tangential (T) directions. Results: The E and σ results in transverse directions confirmed the general influence of the MC that decreased with increasing MC. However, both E and σ in L direction showed a trend that increased at first, and then decreased when MC increased. The local maximums of stiffness and strength may be associated with straightened non-crystalline cellulose, induced by the penetration of water into the wood cell wall. Using the visualization method for compliance, the tension abilities of poplar and Chinese fir exhibited clear moisture and orthotropic dependency. Conclusion: Both poplar and Chinese fir showed a significantly higher degree of anisotropy in the L, R, and T directions. The results in this study provided first-hand data for wooden construction and wood drying.

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Section: Tensile Modulus Esupporting

confidence: 87%

Section: Tensile Modulus Esupporting

confidence: 78%

Orthotropic Tension Behavior of Two Typical Chinese Plantation Woods at Wide Relative Humidity Range

Kuai

Wang

et al. 2019

Forests

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“…Therefore, the unstable state of wood was caused by changes in MC regardless of the presence of stress bias. When water penetrates the cell wall, moisture molecules not only break and reform the hydrogen bonds, but also provide free volume for the rearrangement of mircofibrils and promote the “rearrangement of the hydrogen bonds” within the polymer network [ 18 , 19 , 20 ]. Samples of VEC, which had been kept under constant condition for a long time, were presumed to be more stable in the course of tensile tests as compared with samples of MSC.…”

Section: Resultsmentioning

confidence: 99%

“…Transient hydrogen bonds form free volume and localized stress in wood cell wall, which disturbs the equilibrium state of the molecular packing mode. Under an external load, the formation of free volume and localized stress accelerates the shear slip between the crystalline and amorphous phases in the cell wall [ 17 , 18 , 19 , 20 ].…”

Section: Introductionmentioning

confidence: 99%

Longitudinal Mechano-Sorptive Creep Behavior of Chinese Fir in Tension during Moisture Adsorption Processes

Peng

Jiang

et al. 2017

Materials

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To provide comprehensive data on creep behaviors at relative humidity (RH) isohume conditions and find the basic characteristics of mechano-sorptive (MS) creep (MSC), the tensile creep behaviors, “viscoelastic creep (VEC)” at equilibrium moisture content and MSC during adsorption process, were performed on Chinese fir in the longitudinal direction under 20%, 40%, 60% and 80% RH (25 °C) and at 1, 1.3, and 1.6 MPa, respectively. The free swelling behavior was also measured, where the climate conditions corresponded with MSC tests. Based on the databases of free swelling, VEC, and MSC, the existence of MS effect was examined, and the application of the rheological model under the assumption of partitioned strain was investigated. The results revealed that both VEC and MSC increased with magnitude of applied stress, and the increasing RH level. Under all RH isohume conditions, the total strain of MSC was greater than that of VEC. The influence of RH level on VEC was attributed to the water plasticization effect, whereas that on MSC was presumed to be the effect of water plasticization and unstable state in the wood cell wall. In addition, the RH level promoted the relaxation behavior in MSC, while it slightly affected the relaxation behavior in VEC. In the future, the rheological model could consider the link between load configuration and the anatomic structural feature of wood.

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“…The increasing degree of n E ″ was obviously higher than the decreasing degree of n E ′, regardless of the ramping rate. Takahashi et al confirmed that the decrease in elasticity is not as great as the increase in damping during the sorption process [ 32 ]. Since cellulose, hemicellulose, and lignin have different absorbability, the extents of hygro-expansion vary within the wood cell walls, providing the shear slip between cellulose and matrix, and leading to a large energy dissipation [ 21 , 24 ].…”

Section: Resultsmentioning

confidence: 99%

Viscoelastic Properties of the Chinese Fir (Cunninghamia lanceolata) during Moisture Sorption Processes Determined by Harmonic Tests

Zhan

Jiang

et al. 2016

Materials

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Measured by harmonic tests, the viscoelastic properties of Chinese fir during moisture sorption processes were examined under three relative humidity (RH) modes: RHramp, RHisohume, and RHstep. The stiffness decreased and damping increased as a function of the moisture content (MC), which is presumed to be the effect of plasticization and an unstable state. The increasing damping was associated with the breaking of hydrogen bonds and the formation of free volume within polymer networks. The changes of loss modulus ratio at 1 and 20 Hz, E″1Hz/E″20Hz, proved the changing trend of the unstable state. Higher ramping rates aggravated the unstable state at the RHramp period, and higher constant RH levels provided more recovery of the unstable state at the RHisohume period. Changes of viscoelastic properties were associated with RH (varied or remained constant), and the application of Boltzmann’s superposition principle is a good approach to simulate viscoelasticity development.

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Influence of variation in modulus of elasticity on creep of wood during changing process of moisture

Cited by 17 publications

References 15 publications

Orthotropic Tension Behavior of Two Typical Chinese Plantation Woods at Wide Relative Humidity Range

Orthotropic Tension Behavior of Two Typical Chinese Plantation Woods at Wide Relative Humidity Range

Longitudinal Mechano-Sorptive Creep Behavior of Chinese Fir in Tension during Moisture Adsorption Processes

Viscoelastic Properties of the Chinese Fir (Cunninghamia lanceolata) during Moisture Sorption Processes Determined by Harmonic Tests

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