Transverse mechanical behaviour and moisture absorption of waterlogged archaeological wood from the Vasa ship

Ljungdahl, Jonas; Berglund, Lars A.

doi:10.1515/hf.2007.048

Cited by 26 publications

(20 citation statements)

References 12 publications

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“…This is attributed to plasticisation of the crosslinked material, by sorbed water increasing the chain mobility of the poly(ethyelene)glycol (PEG) crosslinks. It is well known that PEG acts as a plasticiser within the cell wall matrix of wood, leading to undesirable creep behaviour in large historical structures and also very high levels of water sorption [41].…”

Section: Sorption Isotherms and Hysteresis Of Historic Compared With mentioning

confidence: 99%

Variation in the sorption properties of historic parchment evaluated by dynamic water vapour sorption

Popescu

Hill

Kennedy

2016

Journal of Cultural Heritage

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Section: Sorption Isotherms and Hysteresis Of Historic Compared With mentioning

confidence: 99%

Variation in the sorption properties of historic parchment evaluated by dynamic water vapour sorption

Popescu

Hill

Kennedy

2016

Journal of Cultural Heritage

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“…When it came to the MOE and strength in the tangential direction, the corresponding values were approximately 50% and 30% respectively. It was concluded that this was mainly due to micro-buckling and the more brittle plastic collapse of the ray cells in Vasa earlywood compared with recent European oak [29]. Furthermore, the radial MOE in compression and the radial compression strength were found to be negatively influenced by an increase in PEG content.…”

Section: Mechanical Properties Of Vasa Oak -A Reviewmentioning

confidence: 93%

Strategy for developing a future support system for the Vasa warship and evaluating its mechanical properties

2013

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To maintain the integrity of the Vasa warship after salvage in 1961, conservation treatment with polyethylene glycol was carried out to prevent the collapse of cell walls. This treatment had negative effects on the strength and stiffness of the oak and the hull structure has been found to slowly deform over time. It is of interest to construct a three-dimensional numerical computer model to model and predict the deformation of the warship. This creates difficulties related to the complexity of measuring the detailed material properties that are required as input. In this context, a non-destructive methodology to predict the stiffness of the Vasa oak in terms of moduli of elasticity in the three principal directions of timber at critical positions in the ship would be useful. The twofold aim of the paper is to propose a strategy for a support system and to conduct an on-site assessment of the warship to predict the mechanical properties of the Vasa oak material. This paper also contains an up-to-date review of all essential mechanical data measured on the Vasa oak. The preliminary investigation using an X-ray technique to investigate the density properties produced promising results for future use in the evaluation of the mechanical performance. Based on these results, a procedure to establish the stiffness properties of the Vasa oak in terms of MOE was suggested, using a combination of data from previous measurements, in combination with extended tests on Vasa oak specimens and an X-ray-based density calibration procedure. The general complexity of the Vasa warship can be mainly attributed to large variations in the properties of Vasa oak due to surface degradation, chemical treatment and the disintegration of the cell-wall structure originating from centuries of waterlogged conditions. That causes difficulties when assessing mechanical and physical properties on a structural level. A combination of visual inspection together with X-ray investigation is of great importance to evaluate those properties and to obtain more accurate estimates. The results from evaluating mechanical properties can serve as input in a numerical model and serve as a foundation for decision-making relating to the modification of the support system.

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“…Previous investigations of oak wood from the 17th century warship the Vasa show that both the chemical properties (Almkvist and Persson 2008a ;Lindfors et al 2008 ) and the mechanical properties (Ljungdahl and Berglund 2007 ;Bjurhager et al 2012 ;Svedstr ö m et al 2012 ) are changed compared with recent oak. The alteration of the wood properties and the potential to undergo further degradation is crucial for the long-term preservation of the hull.…”

Section: Introductionmentioning

confidence: 99%

Mimicking of the strength loss in the Vasa: model experiments with iron-impregnated recent oak

2013

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Previous studies of the oak wood of the 17th century warship the Vasa have shown significant changes in the chemical and mechanical properties compared with recent oak. The most important factors contributing to these changes are the incorporation of iron compounds during waterlogging and the uptake of polyethylene glycol (PEG) in the course of the 17 years of preservation treatment. To investigate the effect of iron-dependent oxidative degradation reactions, recent oak wood samples were impregnated with aqueous iron(II) chloride solution (0.1 M ) and thereafter exposed to air or pure oxygen at controlled relative humidity in long-term experiments followed by tensile strength (TS) measurements. The ironimpregnated samples exposed to oxygen displayed significant effects already after 1 week and the reduction in TS was ~ 50 % after 1 year. The samples treated with additional PEG displayed less TS reduction, whereas the addition of cysteine had no effect. The size exclusion chromatography of treated samples showed that the average molecular weight of holocellulose had decreased. The results confirm that iron compounds have a detrimental effect in wood and indicate that PEG might act as an antioxidant for the degradation processes. Concerning the Vasa , it may be concluded that most degradation related to iron compounds and oxidative processes have taken place during the first period of conservation when the wood was exposed to oxygen in a still very humid state. Thus, the current rate of oxidative degradation under the present relatively dry museum conditions should be relatively low.

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Transverse mechanical behaviour and moisture absorption of waterlogged archaeological wood from the Vasa ship

Cited by 26 publications

References 12 publications

Variation in the sorption properties of historic parchment evaluated by dynamic water vapour sorption

Variation in the sorption properties of historic parchment evaluated by dynamic water vapour sorption

Strategy for developing a future support system for the Vasa warship and evaluating its mechanical properties

Mimicking of the strength loss in the Vasa: model experiments with iron-impregnated recent oak

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