Influence of Relative Humidity on the Expansion Coefficient Rate of Bamboo Bundles

Abstract:

Relative humidity (RH) can have a significant impact on bamboo products, leading to issues such as swelling, shrinking, and even cracking. Unfortunately, these effects are often difficult to detect in bamboo bundles. This research aims to investigate how RH affects the moisture expansion coefficient (β) of bamboo bundles. Samples from the stem of the Dendrocalamus genus were dried in an oven at 105 °C until they reached a stable weight. The samples were then hand-pulled and cut to create cross-sections with areas ranging from 0.06 mm² to 0.09 mm² and a length of 60 mm. The expansion coefficient of the bamboo bundles was measured using a tensile test, following the ASTM D3379 standard. This was conducted at a constant temperature of 27 °C and a force of 10 N in a controlled chamber with RH levels between 50% and 85% for a full day, with five replicates for accuracy. The results indicate that the strain in bamboo bundles is influenced by both relative humidity (RH) and tensile load. When the RH ranges from 85% to 50%, the bamboo bundles tend to stretch under tensile load. However, when the RH drops to 50% without tensile load, the bundles can return to their original shape. This suggests that while the initial changes in strain may be small, bamboo bundles gradually experience increased strain over time, and prolonged use could result in more significant alterations. Another important factor to consider when using bamboo bundles is the effect of changes in relative humidity (ΔRH) on the average value of β. Indeed, bamboo bundles need time to absorb or release moisture as the surrounding environment changes. The average value of β tends to decrease dramatically in an exponential decay pattern. When ΔRH exceeds 5% in both charge and discharge conditions, the average value of β can be considered equal and constant, as it becomes extremely small and negligible. However, at ΔRH levels higher than 20%, the average value of β converges to 1.5 x 10-4 (%RH)-1, indicating that the bamboo bundles have already adapted to the surrounding humidity. Therefore, it is crucial to carefully assess application areas with rapid humidity fluctuations when using bamboo bundles to prevent potential damage during use.

• Periodical: Key Engineering Materials (Volume 1028)
• Pages: 3-8
• DOI: https://doi.org/10.4028/p-zymcI6
• Online since: October 2025
• Authors: Panidpim Sawangbunditkun, Itthichai Preechawuttipong*, Robert Peyroux
• Keywords: Bamboo Bundle, Expansion Rate, Natural Materials, Relative Humidity

References

[1] Hashna, N., & Elizabeth Thomas, S. (2016). Sustainable Construction Using Bamboo as Flexural Members. Applied Mechanics and Materials, 857, 273-278.

DOI: 10.4028/www.scientific.net/amm.857.273

[2] Silva, F. J., Rodrigues, F. C., & Moreira, L. E. (2014). Buckling of Masts of Bamboos Bundles. Key Engineering Materials, 634, 379-388.

DOI: 10.4028/www.scientific.net/kem.634.379

[3] Li, H., Zhou, G. Y., & Zhang, H. Y. (2010). Research and Utilization Status of Natural Bamboo Fiber. Advanced Materials Research, 159, 236-241.

DOI: 10.4028/www.scientific.net/amr.159.236

[4] Chawla, K. k. (2016). Fibrous Materials: Cambridge, United Kingdom: Cambridge University Press.

[5] Satyanarayana, K. G., Arizaga, G. G. C., & Wypych, F. (2009). Biodegradable composites based on lignocellulosic fibers—An overview. Progress in Polymer Science, 34(9), 982-1021.

DOI: 10.1016/j.progpolymsci.2008.12.002

[6] Bodig, J., & Jayne, B. A. (1982). Mechanics of Wood and Wood Composites: Van Nostrand Reinhold.

[7] Wang, H., Tian, G., Li, W., Ren, D., Zhang, X., & Yu, Y. (2015). Sensitivity of bamboo fiber longitudinal tensile properties to moisture content variation under the fiber saturation point. Journal of Wood Science, 61(3), 262-269.

DOI: 10.1007/s10086-015-1466-y

[8] Chen, H., Miao, M., & Ding, X. (2009). Influence of moisture absorption on the interfacial strength of bamboo/vinyl ester composites. Composites Part A: Applied Science and Manufacturing, 40(12), 2013-2019.

DOI: 10.1016/j.compositesa.2009.09.003

[9] Santosa, D. P. A., Widiastuti, I., & Suharno. (2021). Mechanical Properties of Bamboo on Virgin and Recycled High-Density Polyethylene Matrix. Journal of Physics: Conference Series, 1808(1).

DOI: 10.1088/1742-6596/1808/1/012009

[10] Kaima, J., Preechawuttipong, I., Jongchansitto, P., & Charoenloe, N. (2020). Effect of Chemical Solution on Tensile Strength of Bamboo Fiber. Paper presented at the 10th International Conference on Mechanical Engineering (TSME-ICOME2019), Pattaya, Thailand.

DOI: 10.1088/1757-899x/886/1/012061

[11] Liu, Z., Hu, W., Jiang, Z., Mi, B., & Fei, B. (2016). Investigating combustion behaviors of bamboo, torrefied bamboo, coal and their respective blends by thermogravimetric analysis. Renewable Energy, 87, 346-352.

DOI: 10.1016/j.renene.2015.10.039

[12] Wang, F., & Shao, Z. (2020). Study on the variation law of bamboo fibers' tensile properties and the organization structure on the radial direction of bamboo stem. Industrial Crops & Products, 152.

DOI: 10.1016/j.indcrop.2020.112521

[13] Information on https://www.tmd.go.th.

[14] Zhong, Z., Zhou, X., He, Z., & Wang, J. (2022). Creep behavior of full-culm Moso bamboo under long-term bending. Journal of Building Engineering, 46.

DOI: 10.1016/j.jobe.2021.103710

[15] Chen, D., Zhu, Q., Zong, Z., Xiang, T., & Liu, C. (2019). The Linear Hygroscopic Expansion Coefficient of Cement-Based Materials and Its Determination. Materials (Basel), 13(1).

DOI: 10.3390/ma13010037