Summary
The dynamic moduli and logarithmic decrement of Rimu (Dacrydium cupressinum) were measured along the grain and perpendicular to it in the frequency range 45–85 kHz using a Marx regenerative oscillator system. The moduli and decrement were observed to exhibit strong dispersions between-20°C and-80°C, the actual temperature being dependent on measurement frequency and moisture content of the sample. The activation enthalpy of the dispersion mechanism varied from 3.9 kcal/mole at moisture contents in excess of 7 % to 6 kcal/mole at lower (1%) moisture content. Impregnation of the wood with solvents produced dispersion effects different from those associated with water impregnation. It is postulated that this mechanical dispersion observed in moisture-bearing wood results from the motion of the adsorbed water molecules.
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The author wishes to thank the Head of the Princes Risborough Laboratory, Building Research Establishment, for the hospitality and facilities provided during his year's residence, and also the Council of the University of New South Wales for their generous allowance of sabbatical leave.
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Dunlop, J.I. Damping loss in wood at mid kilohertz frequencies. Wood Sci.Technol. 12, 49–62 (1978). https://doi.org/10.1007/BF00390010
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DOI: https://doi.org/10.1007/BF00390010