Bregman Avi, Michielssen Eric, Taub Alan
Department of Materials Science and Engineering, University of Michigan, 500 S State St., Ann Arbor, MI 48109, USA.
Department of Electrical Engineering and Computer Science, University of Michigan, 500 S State St., Ann Arbor, MI 48109, USA.
Polymers (Basel). 2019 Jul 25;11(8):1233. doi: 10.3390/polym11081233.
Microwave absorbing materials, particularly ones that can achieve high electromagnetic interference (EMI) absorption while minimizing weight and thickness are in high demand for many applications. Herein we present an approach that relies on the introduction of periodically placed air-filled pores into polymer composites in order to reduce material requirements and maximize microwave absorption. In this study, graphene nano platelet (xGNP)/poly-lactic acid (PLA) composites with different aspect ratio fillers were characterized and their complex electromagnetic properties were extracted. Using these materials, we fabricated non-perfect electrical conductor (PEC) backed, porous composites and explored the effect of filler aspect ratio and pore geometry on EMI shielding properties. Furthermore, we developed and experimentally verified a computational model that allows for rigorous, high-throughput optimization of absorbers with periodic porous geometries. Finally, we extend the modeling approach to explore the effect of pore addition on PEC-backed composites. Our composite structures demonstrated decreased fractions of reflected power and increased fractions of absorbed power over the majority of the X Band due to the addition of periodically arranged cylindrical pores. Furthermore, we showed that for xGNP/PLA composite material, reflection loss can be increased by as much as 13 dB through the addition of spherical pores. The ability to adjust shielding properties through the fabrication of polymer composites with periodically arranged pores opens new strategies for the modeling and development of new microwave absorption materials.
微波吸收材料，尤其是那些能够在最小化重量和厚度的同时实现高电磁干扰（EMI）吸收的材料，在许多应用中都有很高的需求。在此，我们提出一种方法，该方法依赖于在聚合物复合材料中引入周期性排列的充气孔隙，以减少材料需求并最大化微波吸收。在本研究中，对具有不同纵横比填料的石墨烯纳米片（xGNP）/聚乳酸（PLA）复合材料进行了表征，并提取了它们的复电磁特性。使用这些材料，我们制备了以非理想导电体（PEC）为背衬的多孔复合材料，并研究了填料纵横比和孔隙几何形状对EMI屏蔽性能的影响。此外，我们开发并通过实验验证了一个计算模型，该模型允许对具有周期性多孔几何形状的吸收体进行严格的高通量优化。最后，我们扩展了建模方法，以探索添加孔隙对PEC背衬复合材料的影响。由于添加了周期性排列的圆柱形孔隙，我们的复合结构在X波段的大部分区域表现出反射功率分数降低和吸收功率分数增加。此外，我们表明，对于xGNP/PLA复合材料，通过添加球形孔隙，反射损耗可增加多达13 dB。通过制备具有周期性排列孔隙的聚合物复合材料来调节屏蔽性能，可以为新型微波吸收材料的建模和开发开辟新的策略。
