Camacho Hernandez Jesus Nain, Link Guido
Institute for Pulsed Power and Microwave Technology IHM, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
Materials (Basel). 2024 Dec 24;18(1):14. doi: 10.3390/ma18010014.
Estimating the effective permittivity of anisotropic fibrous media is critical for advancing electromagnetic applications, requiring detailed microstructural and orientation analyses. This study introduces innovative approaches for disclosing the orientation and microstructure of fibers, leading to mixing relations. It particularly focuses on two specific fiber configurations: 1. wave-curved fibers and 2. a collection of interconnected fibers. The first approach uses sinusoidal wave fibers, considering their curvature and direction. Conversely, the approach for the interconnected fibers operates on the principle of representing fibers as a collection of straight segments. Investigations on fibrous media for both approaches were performed using numerical calculations at the microwave frequency of 2.45 GHz. Each fibrous medium was treated as an effective medium by using fibers significantly smaller than the microwave wavelength. A thorough comparison was made between the proposed mixing relations, numerical data, and state-of-the-art mixing relations to assess their consistency and validity. The comparison of the proposed approaches with traditional models shows an improved accuracy of up to 70% and 8% for the real and imaginary components of the permittivity, respectively. Additionally, the root-mean-square errors were determined as 0.001 + 0.003 and 0.001 - 0.007 for the sinusoidal and interconnected straight fibers approaches, respectively. In addition, a woven alumina fabric was used to compare the experimental resonance frequency with that from simulations using the permittivity of the fabric estimated by the interconnected straight fibers approach. These findings advance the predictive accuracy of permittivity estimation in fibrous media, providing a robust foundation for engineering applications.
估计各向异性纤维介质的有效介电常数对于推进电磁应用至关重要，这需要详细的微观结构和取向分析。本研究引入了创新方法来揭示纤维的取向和微观结构，从而得出混合关系。它特别关注两种特定的纤维构型：1. 波浪弯曲纤维和2. 相互连接的纤维集合。第一种方法使用正弦波纤维，考虑其曲率和方向。相反，对于相互连接的纤维的方法是基于将纤维表示为直线段集合的原理。在2.45 GHz微波频率下使用数值计算对两种方法的纤维介质进行了研究。通过使用远小于微波波长的纤维，将每种纤维介质视为有效介质。对所提出的混合关系、数值数据和最新混合关系进行了全面比较，以评估它们的一致性和有效性。将所提出的方法与传统模型进行比较，结果表明介电常数实部和虚部的精度分别提高了70%和8%。此外，正弦波纤维和相互连接的直纤维方法的均方根误差分别确定为0.001 + 0.003和0.001 - 0.007。此外，使用编织氧化铝织物将实验共振频率与使用相互连接的直纤维方法估计的织物介电常数进行模拟得到的共振频率进行比较。这些发现提高了纤维介质中介电常数估计的预测精度，为工程应用提供了坚实的基础。
