Abstract
The article offers a perspective on how thermal-modification affects the impact bending strength of five different wood species, an aspect that has not received as much attention as the well-studied static load behavior of thermally-modified timber (TMT). Since the TMTs are mainly employed as outdoor materials, where they may encounter impact forces, a comparative investigation into the flexibility and strength of these materials under impact is useful. This article evaluates different aspects of the TMT, such as deflection, strain in the impact region, the maximum force needed to initiate cracks, and the energy required for rupture. Wood planks from ash, beech, larch, oak, and spruce were thermally modified at 180 and 220 °C. They were cut into test specimens, while a separate set of unmodified specimens from each wood species served as the reference group. The specimens were subjected to an impact 3-point bending test, and an ultra-high-speed camera meticulously recorded the results. The images were processed by the digital image correlation (DIC) method to determine the deflection and strain distribution of the beams during the impact test. The deflection, maximum force, maximum longitudinal strain, and required work for rupture of each group were determined. The results showed that thermal-modification decreases the wood deflection and maximum longitudinal strain by approximately 50 %. In addition, the impact bending strength decreased by nearly 60 %. However, the impact bending strength did not exhibit a statistically significant decrease at 180 °C; in some cases, it even increased.
Funding source: MENDELU Grant Agency
Award Identifier / Grant number: IGA-LDF-22-IP-016
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Research ethics: The research is not associated with any human or animal studies and it was ensured to preserve the rights, safety, dignity, and well-being of all research participants.
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Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
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Competing interests: The authors declare no conflicts of interest regarding this article.
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Research funding: This work was supported by the MENDELU Internal Grant Agency (grant number IGA-LDF-22-IP-016).
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Data availability: The data that support the findings of this study are available from the corresponding author, upon reasonable request.
References
Alén, R., Kotilainen, R., and Zaman, A. (2002). Thermochemical behavior of Norway spruce (Picea abies) at 180–225°C. Wood Sci. Technol. 36: 163–171, https://doi.org/10.1007/s00226-001-0133-1.Search in Google Scholar
Altgen, M. and Militz, H. (2016). Photodegradation of thermally-modified Scots pine and Norway spruce investigated on thin micro-veneers. Eur. J. Wood Wood Prod. 74: 185–190, https://doi.org/10.1007/s00107-015-0980-3.Search in Google Scholar
Altgen, M., Adamopoulos, S., and Militz, H. (2017). Wood defects during industrial-scale production of thermally modified Norway spruce and Scots pine. Wood Mater. Sci. Eng. 12: 14–23, https://doi.org/10.1080/17480272.2014.988750.Search in Google Scholar
Bal, B.C. (2015). Physical properties of beech wood thermally modified in hot oil and in hot air at various temperatures. Maderas. Ciencia y Tecnología 17: 789–798.10.4067/S0718-221X2015005000068Search in Google Scholar
Bal, B.C. and Bektaş, İ. (2013). The effects of heat treatment on some mechanical properties of juvenile wood and mature wood of Eucalyptus grandis. Dry. Technol. 31: 479–485, https://doi.org/10.1080/07373937.2012.742910.Search in Google Scholar
Boonstra, M.J., Van Acker, J., Tjeerdsma, B.F., and Kegel, E.V. (2007). Strength properties of thermally modified softwoods and its relation to polymeric structural wood constituents. Ann. For. Sci. 64: 679–690, https://doi.org/10.1051/forest:2007048.10.1051/forest:2007048Search in Google Scholar
Borrega, M. and Kärenlampi, P.P. (2010). Hygroscopicity of heat-treated Norway spruce (Picea abies) wood. Eur. J. Wood Wood Prod. 68: 233–235, https://doi.org/10.1007/s00107-009-0371-8.Search in Google Scholar
Borůvka, V., Zeidler, A., and Holeček, T. (2015). Comparison of stiffness and strength properties of untreated and heat-treated wood of Douglas fir and alder. BioResources 10: 8281–8294, https://doi.org/10.15376/biores.10.4.8281-8294.Search in Google Scholar
Borůvka, V., Zeidler, A., Holeček, T., and Dudík, R. (2018). Elastic and strength properties of heat-treated beech and birch wood. Forests 9: 197, https://doi.org/10.3390/f9040197.Search in Google Scholar
Candelier, K., Dumarçay, S., Pétrissans, A., Gérardin, P., and Pétrissans, M. (2013). Comparison of mechanical properties of heat treated beech wood cured under nitrogen or vacuum. Polym. Degrad. Stab. 98: 1762–1765, https://doi.org/10.1016/j.polymdegradstab.2013.05.026.Search in Google Scholar
Candelier, K., Hannouz, S., Thévenon, M.F., Guibal, D., Gérardin, P., Pétrissans, M., and Collet, R. (2017). Resistance of thermally modified ash (Fraxinus excelsior L.) wood under steam pressure against rot fungi, soil-inhabiting micro-organisms and termites. Eur. J. Wood Wood Prod. 75: 249–262, https://doi.org/10.1007/s00107-016-1126-y.Search in Google Scholar
Czajkowski, Ł., Olek, W., and Weres, J. (2020). Effects of heat treatment on thermal properties of European beech wood. Eur. J. Wood Wood Prod. 78: 425–431, https://doi.org/10.1007/s00107-020-01525-w.Search in Google Scholar
Čabalová, I., Kačík, F., Lagaňa, R., Výbohová, E., Bubeníková, T., Čaňová, I., and Ďurkovič, J. (2018). Effect of thermal treatment on the chemical, physical, and mechanical properties of pedunculate oak (Quercus robur L.) wood. BioResources 13: 157–170.10.15376/biores.13.1.157-170Search in Google Scholar
Čabalová, I., Výbohová, E., Igaz, R., Kristak, L., Kačík, F., Antov, P., and Papadopoulos, A.N. (2022). Effect of oxidizing thermal modification on the chemical properties and thermal conductivity of Norway spruce (Picea abies L.) wood. Wood Mater. Sci. Eng. 17: 366–375, https://doi.org/10.1080/17480272.2021.2014566.Search in Google Scholar
Čermák, P., Rautkari, L., Horáček, P., Saake, B., Rademacher, P., and Sablík, P. (2015). Analysis of dimensional stability of thermally modified wood affected by re-wetting cycles. Methods 12: 2.10.15376/biores.10.2.3242-3253Search in Google Scholar
Čermák, P., Hess, D., and Suchomelová, P. (2021). Mass loss kinetics of thermally modified wood species as a time–temperature function. Eur. J. Wood Wood Prod. 79: 547–555, https://doi.org/10.1007/s00107-020-01634-6.Search in Google Scholar
ČSN 490115 (1979). Wood. Detection of static bending strength. Czech Standards Institute, Prague, Czech Republic.Search in Google Scholar
ČSN 490117 (1980). Wood. Impact strength in bending. Czech Standards Institute, Prague, Czech Republic.Search in Google Scholar
Esteves, B. and Pereira, H.M. (2009). Wood modification by heat treatment: a review. BioResources 4: 370–404, https://doi.org/10.15376/biores.4.1.esteves.Search in Google Scholar
Fajdiga, G., Zafošnik, B., Gospodarič, B., and Straže, A. (2016). Compression test of thermally-treated beech wood: experimental and numerical analysis. Bioresources 11: 223–234.10.15376/biores.11.1.223-234Search in Google Scholar
Gaff, M., Kačík, F., and Gašparík, M. (2019a). Impact of thermal modification on the chemical changes and impact bending strength of European oak and Norway spruce wood. Compos. Struct. 216: 80–88, https://doi.org/10.1016/j.compstruct.2019.02.091.Search in Google Scholar
Gaff, M., Kačík, F., Sandberg, D., Babiak, M., Turčani, M., Niemz, P., and Hanzlík, P. (2019b). The effect of chemical changes during thermal modification of European oak and Norway spruce on elasticity properties. Compos. Struct. 220: 529–538, https://doi.org/10.1016/j.compstruct.2019.04.034.Search in Google Scholar
Gonzalez-Pena, M. and Hale, M. (2009). Colour in thermally modified wood of beech, Norway spruce and Scots pine. Part 1: colour evolution and colour changes. Holzforschung 63: 385–393, https://doi.org/10.1515/HF.2009.078.Search in Google Scholar
Glass, S.V., Cai, Z., Wiedenhoeft, A.C., Ross, R.J., Wang, X., Hunt, C.G., Frihart, C.R., Kretschmann, D.E., Wacker, J.P., Lebow, S., et al.. (2010). Wood handbook: wood as an engineering material, Centennial edition.Search in Google Scholar
Gunduz, G., Aydemir, D., and Karakas, G. (2009). The effects of thermal treatment on the mechanical properties of wild pear (Pyrus elaeagnifolia Pall.) wood and changes in physical properties. Mater. Des. 30: 4391–4395, https://doi.org/10.1016/j.matdes.2009.04.005.Search in Google Scholar
Hassan Vand, M., Tippner, J., and Brabec, M. (2023). Effects of species and moisture content on the behaviour of solid wood under impact. Eur. J. Wood Prod., https://doi.org/10.1007/s00107-023-01986-9.Search in Google Scholar
Hill, C.A., Ramsay, J., Keating, B., Laine, K., Rautkari, L., Hughes, M., and Constant, B. (2012). The water vapour sorption properties of thermally modified and densified wood. J. Mater. Sci. 47: 3191–3197, https://doi.org/10.1007/s10853-011-6154-8.Search in Google Scholar
Hill, C., Altgen, M., and Rautkari, L. (2021). Thermal modification of wood. A review: chemical changes and hygroscopicity. J. Mater. Sci. 56: 6581–6614, https://doi.org/10.1007/s10853-020-05722-z.Search in Google Scholar
Hlásková, L., Procházka, J., Novák, V., Čermák, P., and Kopecký, Z. (2021). Interaction between thermal modification temperature of spruce wood and the cutting and fracture parameters. Materials 14: 6218, https://doi.org/10.3390/ma14206218.Search in Google Scholar PubMed PubMed Central
Hughes, M., Hill, C., and Pfriem, A. (2015). The toughness of hygrothermally modified wood. Holzforschung 69: 851–862, https://doi.org/10.1515/hf-2014-0184.Search in Google Scholar
Humar, M., Lesar, B., and Kržišnik, D. (2020). Moisture performance of façade elements made of thermally modified Norway spruce wood. Forests 11: 348, https://doi.org/10.3390/f11030348.Search in Google Scholar
Iraola, B. and Cabrero, J.M. (2016). An algorithm to model wood accounting for different tension and compression elastic and failure behaviors. Eng. Struct. 117: 332–343, https://doi.org/10.1016/j.engstruct.2016.03.021.Search in Google Scholar
Korkut, S., Korkut, D.S., Kocaefe, D., Elustondo, D., Bajraktari, A., and Çakıcıer, N. (2012). Effect of thermal modification on the properties of narrow-leaved ash and chestnut. Ind. Crops Prod. 35: 287–294, https://doi.org/10.1016/j.indcrop.2011.07.016.Search in Google Scholar
Kubovský, I., Kačíková, D., and Kačík, F. (2020). Structural changes of oak wood main components caused by thermal modification. Polymers 12: 485, https://doi.org/10.3390/polym12020485.Search in Google Scholar PubMed PubMed Central
Kubojima, Y., Okano, T., and Ohta, M. (2000). Bending strength and toughness of heat-treated wood. J. Wood Sci. 46: 8–15, https://doi.org/10.1007/bf00779547.Search in Google Scholar
Larsson Brelid, P. (2013). Benchmarking and state of the art for modified wood. SP Technical Research Institute of Sweden, Stockholm, Sweden, pp. 1–31.Search in Google Scholar
Leijten, A.J.M. (2004). Heat treated wood and the influence on the impact bending strength. Heron 49: 349–360.Search in Google Scholar
Majano, M.A.M., Hughes, M., and Fernández-Cabo, J.L. (2010). A fracture mechanics study of thermally modified beech for structural applications. In: WCTE world conference on timber engineering, Riva del Garda, Trento, Italy, pp. 20–24.Search in Google Scholar
Majano-Majano, A., Hughes, M., and Fernandez-Cabo, J.L. (2012). The fracture toughness and properties of thermally modified beech and ash at different moisture contents. Wood Sci. Technol. 46: 5–21, https://doi.org/10.1007/s00226-010-0389-4.Search in Google Scholar
Metsä-Kortelainen, S. and Viitanen, H. (2009). Decay resistance of sapwood and heartwood of untreated and thermally modified Scots pine and Norway spruce compared with some other wood species. Wood Mater. Sci. Eng. 4: 105–114, https://doi.org/10.1080/17480270903326140.Search in Google Scholar
Metsä-Kortelainen, S., Paajanen, L., and Viitanen, H. (2011). Durability of thermally modified Norway spruce and Scots pine in above-ground conditions. Wood Mater. Sci. Eng. 6: 163–169, https://doi.org/10.1080/17480272.2011.567338.Search in Google Scholar
Moliński, W., Roszyk, E., Jabłoński, A., Puszyński, J., and Cegieła, J. (2018). Mechanical parameters of thermally modified ash wood determined on compression in tangential direction. Maderas. Ciencia y Tecnología 20: 267–276.10.4067/S0718-221X2018005021001Search in Google Scholar
Navi, P. and Sandberg, D. (2012). Thermo-hydro-mechanical processing of wood. EPFL Press, Lausanne, Switzerland.10.1201/b10143Search in Google Scholar
Pelaez-Samaniego, M.R., Yadama, V., Lowell, E., and Espinoza-Herrera, R. (2013). A review of wood thermal pretreatments to improve wood composite properties. Wood Sci. Technol. 47: 1285–1319, https://doi.org/10.1007/s00226-013-0574-3.Search in Google Scholar
Pleschberger, H., Teischinger, A., Müller, U., and Hansmann, C. (2014). Change in fracturing and colouring of solid spruce and ash wood after thermal modification. Wood Mater. Sci. Eng. 9: 92–101, https://doi.org/10.1080/17480272.2014.895418.Search in Google Scholar
Prentice, H.J., Proud, W.G., Walley, S.M., and Field, J.E. (2010). The use of digital speckle radiography to study the ballistic deformation of a polymer bonded sugar (an explosive simulant). Int. J. Impact Eng. 37: 1113–1120, https://doi.org/10.1016/j.ijimpeng.2010.05.003.Search in Google Scholar
Rapp, A., Brischke, C., and Welzbacher, C. (2006). Interrelationship between the severity of heat treatments and sieve fractions after impact ball milling: a mechanical test for quality control of thermally modified wood. Holzforschung 60: 64–70, https://doi.org/10.1515/HF.2006.012.Search in Google Scholar
Rautkari, L., Honkanen, J., Hill, C.A., Ridley-Ellis, D., and Hughes, M. (2014). Mechanical and physical properties of thermally modified Scots pine wood in high pressure reactor under saturated steam at 120, 150 and 180°C. Eur. J. Wood Prod. 72: 33–41, https://doi.org/10.1007/s00107-013-0749-5.Search in Google Scholar
Sandberg, D., Kutnar, A., Karlsson, O., and Jones, D. (2021). Wood modification technologies: principles, sustainability, and the need for innovation, 1st ed. CRC Press/Taylor & Francis Group, Boca Raton, FL, USA.10.1201/9781351028226-1Search in Google Scholar
Schneeweiß, G. and Felber, S. (2013). Review on the bending strength of wood and influencing factors. Am. J. Mater. Sci. 3: 41–45.Search in Google Scholar
Srinivas, K. and Pandey, K.K. (2012). Effect of heat treatment on color changes, dimensional stability, and mechanical properties of wood. J. Wood Chem. Technol. 32: 304–316, https://doi.org/10.1080/02773813.2012.674170.Search in Google Scholar
Widmann, R., Fernandez-Cabo, J.L., and Steiger, R. (2012). Mechanical properties of thermally modified beech timber for structural purposes. Eur. J. Wood Wood Prod. 70: 775–784, https://doi.org/10.1007/s00107-012-0615-x.Search in Google Scholar
Yildiz, U.C., Yildiz, S., and Gezer, E.D. (2005). Mechanical and chemical behavior of beech wood modified by heat. Wood Fiber Sci. 37: 456–461.Search in Google Scholar
Yildiz, S., Gezer, E.D., and Yildiz, U.C. (2006). Mechanical and chemical behavior of spruce wood modified by heat. Build. Environ. 41: 1762–1766, https://doi.org/10.1016/j.buildenv.2005.07.017.Search in Google Scholar
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