Studies on change of strain developed in different wood samples due to change in relative humidity

In this paper the dimensional change of different varieties of wood blocks due to change in relative humidity (RH) is presented. The dimensional change of wood due to variation of RH is measured in terms of strain. For this purpose, a strain measuring system is developed in the laboratory. The developed system is used to measure temperature, RH and strain of wood samples due to change in RH. Seventeen wood blocks of different thickness and different orientations are studied. Out of these, strain sensitivity of three samples covering the measured range of values is presented in this paper. The strain variation of the wood samples is tested in different humidity levels generated by the method of binary salt solutions at constant temperature 25 °C. The results obtained show different levels of strain developed in different species of wood. The change of strain is found to depend on the types of wood, thickness of the samples and orientations. Keywords: Dimensional change, Relative humidity, Strain, Wood bloc