In this paper, a novel soluble copoly(aryl ether nitrile) containing phthalazinone and biphenyl moieties (PPBEN) was synthesized for the first time to improve the impact resistance of tetraglycidyl 4,4'-diaminodiphenylmethane epoxy resin cured with 4,4-diaminodiphenylsulfone. Then a series of blends were prepared via solution blending with different contents of PPBEN. The thermal and mechanical properties and the micromorphology of the cured blends were investigated by differential scanning calorimetry, dynamic mechanical analysis (DMA), parallel plate rheometry, mechanical property tests and SEM analysis, respectively. The results indicated that the incorporation of thermoplastic PPBEN delayed the epoxy curing reaction, and the crosslinking density of epoxies was also reduced. The no-notch impact strength of the cured blend with 15% PPBEN was up to 16.7 kJ m −2 , higher by about 104% than that of pure epoxy resin without sacrificing the modulus due to a specific sea-island structure. All the blends showed two-phase morphology characterized by DMA and SEM. The size of the thermoplastic morphology was only 70−80 nm, much less than that of commonly used thermoplastics, due to the special segment structure of PPBEN.

In this paper, an approach is proposed to realize optically transparent metamaterial absorber (OTMA) with ultra-broadband absorption properties by using composite resonant structure. The indium tin oxide (ITO) resistive film is used to construct the resonant structure to induce high ohmic loss and broaden the bandwidth of the resonances, thus achieves more than 90% absorptivity in the wide bandwidth of 8-30.3 GHz, which can cover the X and Ku bands of the airborne and surveillance radar signal frequencies. The novelty of designed structure lies in the properties of larger absorption bandwidth (covering X, Ku, K and part of Ka bands), lower thickness, and absorption capacity over a wide range of incident angles. Moreover, by replacing the intermediate air spacer with polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA) dielectrics, the OTMAs that can be used for conformal applications and rigid window glass of stealth armament are designed. This strategy provides more flexibility for the applications of broadband OTMA in different occasions, and has potential application prospects in radar stealth system, EM shielding and transparent RF equipment fields. The average optical transmittance of the whole structure in the visible light range exceeds 78%.

In this work, 3 dB branch‐line waveguide in the range of 335‐415 GHz directional coupler is proposed, where the insertion loss is less than 0.9 dB and the directionality is better than 20 dB. The coupler is composed of three “crossing”‐shaped structures, which can effectively enhance the directionality and coupling, based on a certain broad bandwidth. The designed coupler has been modeled and optimized, using commercial full‐wave simulation software HFSS, fabricated by the UV‐LIGA process. In addition, its deformation was theoretically analyzed at different pressures by ANSYS software to test its practicability. Both of the test and simulated results have a nice correlation. We conclude that our proposed coupler has excellent performance and can be used for the investigation of submillimeter wave components in terahertz applications.

A validating approach for electromagnetic thermal (EMT) conversion of a composite broadband absorbent metamaterials (AMs) is proposed in this paper. The integrated multilayer AMs consisting of top square loop (Q-loops) array layer, middle metal plate-polymer sandwich, bottom Q-loops array layer stacked vertically is analyzed with finite-different time-domain (FDTD) algorithm and fabricated by High Density Interconnector (HDI) process and Micro-electromechanical Systems (MEMS) technology. The implemented composite layered structure with the dielectrics and subsequent multi metal loops has broadband bandwidth over 2.5GHz in X-bands. High absorption performance in various incident waves with different polarizations and incident angles basically maintains a fixed efficient level of the AMs with diverse absorbing states in wide operating band. Electromagnetics and thermal multiphysics analysis validates the EMT conversion of the AMs in induced strong electromagnetic resonance. The integrated thermal conduction device is loaded on the back of AMs to transfer the converted thermal energy in time, which effectively reduces the surface thermal distribution. Finally, absorbent properties tested by free space methods and thermocouple and infrared thermal imaging (ITI) system shows the polarization independent energy transformation in greatly accordance with numerical analysis. This investigation shows the potential application of AMs in stealth systems to achieve both electromagnetic stealth and infrared thermal stealth through EMT energy conversion.INDEX TERMS Broadband, Absorbent metamaterials (AMs), Electromagnetic thermal (EMT) conversion, Stealth, Thermoelectricity.