Influence of moisture on the vibro-mechanical properties of bio-engineered wood
- 306 Downloads
In this study, changes in the vibro-mechanical properties of fungi-treated wood, during sorption and desorption at different humidity levels, were investigated. Norway spruce resonance wood (with uniform narrow annual rings and high tonal quality for musical instrument craftsmanship) was incubated with Physisporinus vitreus for 36 weeks. Stiffness, internal friction, and tonal performance indices of control (untreated) and fungi-treated wood were compared after exposure to a stepwise variation of relative humidity. It was demonstrated that fungal treatment increased the internal friction and decreased the specific modulus of elasticity, during reduction of wood density. Internal friction of both control and fungi-treated wood significantly increased during dynamic sorption, especially during early stages (hours) of each humidity change step. Both specific modulus of elasticity and internal friction showed a hysteretic behavior during humidity variation cycles. Hysteresis was smaller in fungi-treated wood. Also, tonal performance indices were improved after fungal treatment and showed a reduced variation at different relative humidity conditions. Dynamic vapor sorption tests and FT-IR microscopy studies revealed changes in hygroscopicity and the supramolecular structure of wood, which may explain the observed vibrational behavior. Less dependency of wood vibrational properties to the variation of the ambient humidity is important for the acoustic performance of string instruments.
KeywordsLignin Moisture Content Internal Friction Equilibrium Moisture Content Moisture Sorption
We would like to acknowledge the financial support of the Walter Fischli Foundation and help of our bio-engineering wood team and also Michael Baumgartener for introducing us the practical aspects of instrument making. We also thank Daniel Heer for the sample preparation, Beatrice Fischer for her comments on FT-IR, and Iris Bérmaud for making it possible to use her developed vibrational testing hard- and soft-ware.
- 3.Skaar C (1998) Wood–water relations. Springer-Verlag, BerlinGoogle Scholar
- 4.Sasaki T, Norimoto M, Yamada T, Rowell RM (1988) Effect of moisture on the acoustical properties of wood. J Jpn Wood Res Soc 34(10):794–803Google Scholar
- 5.Quarles SL (1990) Effect of moisture content and ring angle on the propagation of acoustic signals in wood. J Acoust Emiss 9(3):189–195Google Scholar
- 6.Akitsu H, Norimoto M, Morooka T, Rowell RM (1993) Effect of humidity on vibrational properties of chemically modified wood. Wood Fiber Sci 25(3):250–260Google Scholar
- 8.Hernandez RE (2007) Moisture sorption properties of hardwoods as affected by their extraneous substances, wood density, and interlocked grain. Wood Fiber Sci 39:132–145Google Scholar
- 12.Ganne-Chédeville C, Jääskeläinen AS, Froidevaux J, Hughes M, Navi P (2012) Natural and artificial ageing of spruce wood as observed by FTIR-ATR and UVRR spectroscopy. Holzforschung 66:163–170Google Scholar
- 16.European Committee for Standardization, European Standard EN 113 (1997) Wood preservatives: test method for determining the protective effectiveness against wood destroying basidiomycetes. In: Determination of toxic values. European Committee for Standardization, BrusselsGoogle Scholar
- 19.Brémaud I (2006) Diversite´ des bois utilise´s ou utilisables en facture d’instruments de musique (Diversity of woods used or usable in musical instruments making). PhD dissertation, University of Montpellier II, FranceGoogle Scholar
- 20.Lehringer C, Koch G, Adusumalli RB, Mook WM, Richter K, Militz H (2011) Effect of Physisporinus vitreus on wood properties of Norway spruce. Part 1: aspects of delignification and surface hardness. Holzforschung 65:711–719Google Scholar
- 24.Gilani MS, Schwarze FWMR (2014) Hygric properties of Norway spruce and sycamore after incubation with white rot fungi. Holzforschung. doi: 10.1515/hf-2013-0247