The influence of moisture content on the fracture behaviour of Norway spruce when tension is applied in the direction of the grain
2004
Szalai, J. (University of Forestry and Wood Sciences, Sopron (Hungary). Department of Technical Mechanics) | Niemz, P. | Andor, K. | Bariska, M. | Howald, M.T.
The tensile strength of some 300 Norway spruce samples was tested parallel to the grain on samples with diverse moisture content. The objective of the investigation was to determine the influence of moisture content on the tensile strength behaviour of the wood and on the type of the frequency distribution of the data. Specifically, we investigated whether the fracture mechanism changed with increasing moisture content. The frequency distribution of the data was compared with four distribution models: the normal, the lognormal, the Pearson III and the Weibull distribution. According to the results, the tensile strength rose to around 10% in samples with a lower moisture content. After reaching the maximum below the level of fibre saturation, it falls back, almost linearly. The data frequency histogram is best approximated by the Weibull and the Pearson III distributions. We conclude that brittle type fracture prevails, irrespective of the level of moisture content.
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