Optimization and Modeling of Sound-Absorption Properties of Natural Fibers for Acoustical Application

ABSTRACT

Kenaf fibers have long been utilized because of their remarkable properties, such as availability, durability, and strength. Recently, they have also been used as sound-absorbing composites for noise control purposes. This paper investigates the possibility of improving the tensile strength of kenaf fibers through optimizing the alkaline treatment process. It also considers the effects of such optimization on the acoustic absorption coefficients of the samples fabricated from these treated kenaf fibers as well as the applicability of the numerical model to predict the acoustic absorption. Having employed the response surface methodology (RSM) to optimize the alkaline treatment process and achieve optimal conditions for the kenaf fibers, the scanning electron microscopy (SEM) and tensile test were used to study and compare the morphological and tensile properties of raw fibers (nonoptimal) and the fibers treated in optimal conditions. Several cylindrical samples with constant thickness and density (30 mm and 200 kg/m³) were then made of fibers treated in optimal conditions. The sound absorption coefficient, porosity, and airflow resistivity of these samples were measured based using ISO 10534–2 (impedance tube system), SEM and ASTM C423-09A, respectively. The results demonstrated that the tensile strength of optimally treated fibers increased by 182.39%. The acoustic absorption coefficients of the samples fabricated from these fibers were also higher at all frequencies (low-, mid-, and high-frequency range) compared with samples made of untreated fibers in a way that the Sound Absorption Average value of the former increased by 17.97%. Moreover, it was found that inverted Dunn and Davern model via Nelder-Mead simplex method well follows the sound absorption pattern from the experimental results in the overall frequency range. The use of multifaceted improvement approaches for natural materials such as kenaf fibers increases the usability of these materials as sustainable and eco-friendly alternatives in the engineering process of manufacturing sound-absorbing materials.

摘要

红麻纤维因其优异的可用性、耐久性、强度等性能而被广泛应用. 最近，它们也被用作吸声复合材料，用于噪声控制. 探讨了通过优化碱处理工艺提高红麻纤维拉伸强度的可能性. 文中还考虑了这种优化对红麻纤维的吸声系数的影响，以及数值模型预测吸声系数的适用性. 采用响应面法（RSM）优化了碱处理工艺，实现了红麻纤维的最佳条件，采用扫描电子显微镜（SEM）和拉伸试验研究并比较了未经优化处理的纤维和在优化条件下处理的纤维的形态和拉伸性能. 然后用在最佳条件下处理过的纤维制成几个具有恒定厚度和密度（30mm和200kg/m3）的圆柱形样品. 分别采用ISO10534-2（阻抗管系统）、SEM和ASTMC423-09A测试了样品的吸声系数、孔隙率和气流阻力. 结果表明，优化后的纤维拉伸强度提高了182.39%. 与未经处理的纤维相比，由这些纤维制备的样品在所有频率（低频、中频和高频范围）下的吸声系数都更高，前者的吸声平均值（SAA）提高了17.97%。此外，利用Nelder-Mead单纯形（NMS）方法建立的Dunn and Davern模型在整个频率范围内都能很好地模拟实验结果中的吸声规律. 对天然材料（如红麻纤维）采用多方面的改进方法，提高了这些材料在制造吸声材料的工程过程中作为可持续和环保替代品的可用性.

KEYWORDS:

• Kenaf fiber
• chemical treatment
• morphology
• acoustic absorption
• numerical model
• inverse method

关键词:

• 红麻纤维
• 化学处理
• 形态
• 吸声
• 数值模型
• 反演方法

Acknowledgments

We are thankful to Tarbiat Modares University for providing the necessary laboratory facilities for this work.

Disclosure statement

The authors declare that there is no conflict of interests regarding the publication of this paper.

Additional information

Funding

This work was supported by the Iran National Science Foundation (INSF) [98029526].