Dynamic mechanical analysis (DMA) of waterlogged archaeological wood at room temperature

Pizzo, Benedetto; Pecoraro, Elisa; Lazzeri, S.

doi:10.1515/hf-2017-0114

Cited by 20 publications

(18 citation statements)

References 46 publications

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“…First of all, except for oak heartwood, the storage modulus of archaeological wood was significantly lower in comparison with contemporary wood, which reflects its calculated loss of wood substance (about 70–80%), the resulting lower density and reduced cellulose and hemicelluloses content. It is well-known that wood mechanical parameters strongly depend on density, as well as on cellulose and hemicellulose contents in the cell wall, which account for wood stiffness and mechanical strength [ 67 , 77 , 107 ]. The density of COH examined in the research turned out to be very low for this wood species; moreover, the degree of degradation of AOH was only about 25%; hence, no significant differences in mechanical parameters were observed between them.…”

Section: Resultsmentioning

confidence: 99%

The Viscoelastic Behaviour of Waterlogged Archaeological Wood Treated with Methyltrimethoxysilane

et al. 2021

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Waterlogged wood treatment with methyltrimethoxysilane (MTMS) proved effective in stabilising wood dimensions upon drying (anti-shrink efficiency of 76–93%). Before the method can be proposed as a reliable conservation treatment, further research is required that includes the evaluation of the mechanical properties of treated wood. The aim of the study was to characterise the effect of the treatment on the viscoelastic behaviour of archaeological waterlogged elm and oak wood differing in the degree of degradation. Dynamic mechanical analysis in the temperature range from −150 to +150 °C was used for the study. To better understand the viscoelastic behaviour of the treated wood, pore structure and moisture properties were also investigated using Scanning Electron Microscopy, nitrogen sorption, and Dynamic Vapour Sorption. The results clearly show that methyltrimethoxysilane not only prevents collapse and distortions of the degraded cell walls and decreases wood hygroscopicity (by more than half for highly degraded wood), but also reinforces the mechanical strength by increasing stiffness and resistance to deformation for heavily degraded wood (with an increase in storage modulus). However, the MTMS also has a plasticising effect on treated wood, as observed in the increased value of loss modulus and introduction of a new tan δ peak). On the one hand, methyltrimethoxysilane reduces wood hygroscopicity that reflects in lower wood moisture content, thus limiting the plasticising effect of water on wood polymers, but on the other hand, as a polymer itself, it contributes to the viscous behaviour of the treated wood. Interestingly, the effect of silane differs with both the wood species and the degree of wood degradation.

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Section: Resultsmentioning

confidence: 99%

The Viscoelastic Behaviour of Waterlogged Archaeological Wood Treated with Methyltrimethoxysilane

et al. 2021

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“…The ratio E /E (tanδ) varies with the frequency, depending on the degree of wood degradation; it is higher for slightly decayed wood, while for severely degraded wood, the tanδ values at low frequencies are lower (or similar) than for sound wood of the same species. The DMA technique can then serve as a useful tool for identification of the state of waterlogged wood preservation (in both a wet and a dry state), based on the magnitude of the storage and loss modulus and the changes in secondary relaxation peaks in the loss factor (their location and intensity) [42,93].…”

Section: Physical Degradationmentioning

confidence: 99%

Conservation of Waterlogged Wood—Past, Present and Future Perspectives

Broda

Hill

2021

Forests

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This paper reviews the degradation, preservation and conservation of waterlogged archaeological wood. Degradation due to bacteria in anoxic and soft-rot fungi and bacteria in oxic waterlogged conditions is discussed with consideration of the effect on the chemical composition of wood, as well as the deposition of sulphur and iron within the structure. The effects on physical properties are also considered. The paper then discusses the role of consolidants in preserving waterlogged archaeological wood after it is excavated as well as issues to be considered when reburial is used as a means of preservation. The use of alum and polyethylene glycol (PEG) as consolidants is presented along with various case studies with particular emphasis on marine artefacts. The properties of consolidated wood are examined, especially with respect to the degradation of the wood post-conservation. Different consolidants are reviewed along with their use and properties. The merits and risks of reburial and in situ preservation are considered as an alternative to conservation.

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“…In measuring viscoelasticity and related storage modulus loss modulus, the DMA method is highly effective [22]. Previously, some scholars have obtained the storage modulus and loss modulus of waterlogged archaeological wood by DMA under vibration load using small samples [23,24]. However, there were no reports about thermal expansion coefficient or the mechanical properties testing of archaeological wood by TMA.…”

Section: Introductionmentioning

confidence: 99%

A Quasi-Nondestructive Evaluation Method for Physical-Mechanical Properties of Fragile Archaeological Wood with TMA: A Case Study of an 800-Year-Old Shipwreck

Han

Qin

et al. 2022

Forests

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Archaeological wood is a kind of ‘new material’ that has deteriorated due to long-term degradation. The existing wood science theory and evaluation methods are not fully applicable to archaeological wood. Moreover, current physical-mechanical evaluation methods are inadequate for fragile archaeological wood due to their insufficient accuracy and the large sample amount required, causing difficulties in many necessary physical-mechanical repeatability tests. In light of these limitations, the representative samples on Nanhai No. 1, a merchant shipwreck in the Song Dynasty, were selected as the research objects in this paper. The shipwreck is a typical waterlogged wooden artifact. A quasi-nondestructive physical-mechanical evaluation technique for archaeological wood was developed with the thermomechanical analyzer (TMA). This study used TMA to evaluate the bending strength of representative waterlogged archaeological samples of Nanhai No. 1 shipwreck and sound wood with the same species. Besides, the thermal linear expansion coefficients in the ambient temperature range were obtained. The sizes of the samples used in the tests were only 2 mm × 8 mm × 0.3 mm and 1 cm × 1 cm × 1 cm, respectively. Bending strength results of archaeological wood by the TMA method conformed to the tendency that the bending strength decreases with the increase of decay degree. In addition, the longitudinal linear expansion coefficients of archaeological wood reached 80%–115% of those in the transverse grain direction, which were about 10 times higher than those of the sound wood. The linear expansion coefficients of archaeological wood in three directions were similar. Based on the results of Fourier transform infrared analysis (FT-IR), the significant differences in the physical-mechanical properties of the archaeological wood and the sound wood were induced to be mainly ascribed to the decomposition and the loss of hemicellulose in the archaeological wood. The cell wall substrate could not stabilize the cellulose skeleton, which led to the instability of the tracheid structure of the archaeological wood. This study provided a proven quasi-nondestructive method for the preservation state evaluation of waterlogged archaeological wood (WAW) from the Nanhai I shipwreck and other similar waterlogged wooden relics.

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Dynamic mechanical analysis (DMA) of waterlogged archaeological wood at room temperature

Cited by 20 publications

References 46 publications

The Viscoelastic Behaviour of Waterlogged Archaeological Wood Treated with Methyltrimethoxysilane

The Viscoelastic Behaviour of Waterlogged Archaeological Wood Treated with Methyltrimethoxysilane

Conservation of Waterlogged Wood—Past, Present and Future Perspectives

A Quasi-Nondestructive Evaluation Method for Physical-Mechanical Properties of Fragile Archaeological Wood with TMA: A Case Study of an 800-Year-Old Shipwreck

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