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Based on the research basis of single-layer cross-shaped frequency selective fabrics, the electromagnetic transmission characteristics of double-layer and three-layer cross-shaped frequency selective fabrics were explored in this paper. The frequency selective fabrics with different multilayer structures and specific-sized conductive units were designed, and then prepared by the computer engraving method and tested using the free-space method. The results show that the single-layer sample is less affected by the polarization mode of the electromagnetic wave, while the effect of the incidence angle is slightly larger. For the frequency selective fabric samples with the same frequency selective surface layers, the frequency selective characteristics of the double-layer samples are more ideal than those of the single-layer samples, while the electromagnetic loss of the three-layer samples is large and the narrow-band transmission characteristic is weakened. For the frequency selective fabric samples with the complementary frequency selective surface layers, the double-layer sample mainly shows band-pass characteristics and the narrow-band transmission characteristics are better than the single-layer sample. The three-layer sample of ‘patch + aperture + patch’ presents band-pass characteristics, and the ‘aperture + patch + aperture’ sample generates resonance at multiple frequency points, but the resonance peaks are all less than –10.00 dB, meaning that the sample presents full shielding characteristics in the test frequency band. The equivalent circuit model was built to explore the electromagnetic transmission mechanism, revealing the fabric type and structure, and the conductive unit type and size will affect the equivalent impedance of the frequency selective fabrics, thus further influencing the electromagnetic transmission characteristics.

In this paper, frequency selective fabrics (FSFs) with narrow-band transmission characteristics were proposed. The square-ring FSF was taken as an instance to illustrate the design principle. Based on the existing theoretical basis and by means of software simulation and optimization, the optimum structures with ideal narrow-band band-stop or band-pass characteristics were obtained. Then, the practical specimens were manufactured through a computer-based carving process and measured using the transmission method in an anechoic chamber. Two structural models were respectively simulated using two different algorithms and the results showed very small differences, primarily verifying the effectiveness of the design methods and reasonability of the model simplification. The measured and simulated transmission characteristics of square-ring FSFs were compared and showed a high consistency, which further verified the validation of the design method. The other two kinds of FSFs, namely Jerusalem-shaped and circle/ring hybrid FSFs, were designed and measured, which showed the narrow-band frequency selective characteristics were quite ideal. This indicates that the proposed design method using simulation software may be applied to many different structures and has directive sense in the related product design and development process.

In this paper, a novel kind of electromagnetic (EM) functional textiles is proposed, which show high-pass characteristics as they interact with EM waves. The periodically conductive woven fabric was designed, fabricated, and measured. Specifically, by means of unit cell model building and EM simulation, the theoretical S21 (transmission coefficient) and S11 (reflection coefficient) curves were obtained. A concrete sample was fabricated through weaving process, and its transmission characteristics were measured in the microwave anechoic chamber. The measured and simulated results were highly consistent, demonstrating the validity of design process. Compared with the aluminum foil paper sample, the S21 values of fabricated sample were a little smaller, and the reason could be attributed to yarn crimp and surface roughness. The EM characteristics of fabricated sample under two different polarization modes were slightly different, which was due to the beating-up tension of weaving process. The work could offer new research ideas, and the related products have potential advantages over rigid plates on the account of textile characteristics.

The interfacial structure and binding forces of polytrimethylene terephthalate/polyethylene terephthalate filament were investigated through the methods of Carbon-13 nuclear magnetic resonance (13C-NMR), differential scanning calorimeter (DSC), scanning electron microscopy (SEM) and optical microscopy. When two molten polymers met during the spinning process, an interface layer between the PTT and PET components formed and played an important role in binding the two components together. When the blending time was sufficient, an ester-interchange reaction took place with the generation of the copolymer. The PET recrystallisation was observed in the DSC curve under the influence of entangled PTT molecular chains. The morphology of the cross-section and side view proved that the linear boundary line was short and weaker in binding without a chemical bond and molecular diffusion. Side-by-side bi-component fiber and split-type fiber was able to be controllably spun by adjusting the spinning parameters.