As the basic materials with specific properties, fabrics have been widely applied in electromagnetic (EM) wave protection and control due to their characteristics of low density, excellent mechanical properties as well as designability. According to the different mechanisms and application scenarios on EM waves, fabrics can be divided into three types: EM shielding fabric, wave-absorbing fabric and wave-transparent fabric, which have been summarized and prospected from the aspects of mechanisms and research status, and it is believed that the current research on EM wave fabrics are imperfect in theory. Therefore, in order to meet the needs of different EM properties and application conditions, the structure of fabrics will be diversified, and more and more attentions should be paid to the research on structure of fabrics that meets EM properties, which will be conductive to guiding the development and optimization of fabrics. Furthermore, the application of fabrics in EM waves will change from 2D to 3D, from single structure to multiple structures, from large to small, as well as from heavy to light.
The partial fiber breaking in the warp yarn of three-dimensional (3D) woven fabrics needs to be urgently reduced considering the large shedding displacement and repeated yarn frictions in the fabricating process. A kinematical model of the heald frame was established in order to analyze the impact and wear of the warp yarn in the shedding process of 3D weaving. The variation tendency of the friction force between the yarn and heddle eye was obtained and the variable acceleration trajectory of the heald frame based on minimizing the friction and impact load on the yarn was derived. The experimental results showed that the fiber breakage rate in one warp yarn using the derived curve trajectory reduced drastically. The research results are beneficial to the theoretical design of the shedding system of weaving machines for 3D woven fabric.
Conductive fiber plain fabric can be used for manufacturing electromagnetic protective products, due to the capacity of electromagnetic shielding effectiveness and deformability. A model was established to predict the shielding effectiveness of conductive fiber plain fabric. The curved surface of fabric can be decomposed into countless ideal planes. The vertical incidence of electromagnetic waves on plain fabric surface can be regarded as the oblique incidence on the ideal plane. The transmission coefficients of transverse electric and transverse magnetic polarized waves were different in each point of fabric surface through the surface equation. The weight factor was supposed as the value of small area at each incident point, and the weighted average of transmission coefficients was deduced. The results showed that, the values of shielding effectiveness increased with the decrease of the pitch of conductive fiber plain fabric and increased with the increase of frequency in the range of 0.1–2 GHz. The trends of theoretical prediction values were consistent with the simulation and experimental values, which proved the rationality of the model.
Based on the wave absorption model of 3D woven fabric and the zero-reflection equations, a new structural design method of 3D electromagnetic (EM) wave-absorbing woven fabrics was obtained. The 3D woven fabrics fabricated by the proposed method had the structure of a bidirectional angle interlock. Continuous S-2 glass fibers were used as the matching layer of this 3D woven fabric, and continuous carbon fibers were used as the absorbing layer. The absorbing layer satisfied the equivalent EM parameters under the condition of zero reflection. The results of the simulation and experiment showed that the performance trends of the 3D wave-absorbing fabric obtained by this method were consistent with the theory, which verified the correctness of the structure design method. The 3D fabrics obtained by this method have the advantages of wide absorbing frequencies and good absorbing performance (−20 dB). This structural design method also has theoretical guiding significance for the development of 3D wave-absorbing fabrics.
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