Mechanical Design and Manufacturing of Signal Interception Antenna in Composite Material for Naval Application

This work shows the mechanical design and the FE analyses performed for an innovative naval Antenna Unit for signal interception application: more than twenty electromagnetic sensors operating from HF up to Ka band and microwave modules are integrated in a unique structure designed for a top mast installation (i.e. for naval platform). The number of constraints in terms of weight and electromagnetic transparency calls for the employment of composite materials such as glass, aramidic and carbon epoxy prepregs. Primary structures was modelled by using FE codes: both orthotropic and isotropic models have been implemented as well as non-linear contacts and bolted joints. The mast-mounted installation requires high mechanical stiffness and strength but the exposure to saline environment needs many manufacturing issues to be respected. In particular, the selection process of suitable materials and the sealing manufacturing procedures to protect them from the external agents was reported. Another key feature of the presented design concerns the electromagnetic compatibility requirement: to avoid electromagnetic emissions (EMC) generated by antenna’s internal units and to protect antenna sensors by external platform’s emitters, an appropriate stacking sequence was chosen for composite laminates with a prepreg copper mesh.

Electromagnetic Transparency of Composites of Unsaturated Polyester and Nanolignin: Morphological and Surface Energy Considerations

We introduce a simple spray drying method for the scaleup production of spherical organic (lignin) microparticles with controlled size distribution (0.85 to 1.57 mm). We assess the surface energy of the lignin particles by inverse gas chromatography and determine its role in nanocomposites synthesized from unsaturated polyester. Such nanocomposites are shown to be irradiation transparent (millimeter frequency region). The permittivity and tan d of the composite material reached values between 0.01 and 3.1 (28 GHz) with 10 per hundred resin filler content. Vinyl groups were introduced on the surface of the particles to achieve enhanced interfacial adhesion, and resulted in a reduced relative permittivity (2.75). Together with wave interactions, the mechanical and thermal properties of the composites are placed in perspective, opening new opportunities in next generation bio-based devices for 5G high-speed communication.

Design and characterisation of frequency selective conductive materials for electromagnetic fields control

To prevent the electromagnetic (EM) wakefields excitation, protect detectors from damage at a range of installations and facilities including particle accelerators the EM field control is required. Conductive foils or wires providing EM protection and required thermal and mechanical properties are normally used. We suggest novel composite materials with uniquely designed frequency selective conductivity enabling them to overcome the properties of the conventional materials, protect from EM fields and supress undesirable phenomena. Theoretical and experimental investigations are carried out and the conductivity of designed and composite (dual-layer) aluminium/graphene metamaterials as well as graphene and aluminium foils is studied. The EM properties of these materials are compared, and conditions of full and partial electromagnetic transparency are discussed. Results observed allow engineering materials capable of EM field control, instability suppression including those observed in high-intensity particle accelerators and enabling control of an EM field generating media including relativistic charge particle beams.

Bond of GFRP Reinforcement with Concrete

Corrosion of steel reinforcement is the major cause of deterioration of existing RC structures. Combined effects of moisture, temperature, and chlorides reduce the alkalinity of concrete and exacerbate the corrosion of steel reinforcement, especially for concrete structures subjected to aggressive environments, such as marine structures and bridges and parking garages exposed to de-icing salts. Glass fiber reinforcement polymer (GFRP) bars are suitable alternatives to steel bars in reinforced concrete applications if durability, electromagnetic transparency, or ease of demolition in temporary constructions is sought, that have to be demolished partially by tunnel boring machines (TBMs). The bond of GFRP reinforcement is different from steel reinforcing bars. This paper presents factors affecting the bond strength between GFRP reinforcement and concrete.

Achieving broadband electromagnetic transparency with transmission line metamaterials

Electromagnetic transparent device (ETD) capable of protecting the device inside without affecting its performance is a fascinating device with extensive application prospects. In this paper, an equivalent circuit method for realizing ETD using transmission line (TL) metamaterials is presented. The validity of such a method and the transparent effect of the device are demonstrated through the Agilent's Advanced Design System (ADS) circuit simulator. Moreover, the influence of the quality factor of lumped elements on the performance of the device and its broadband characteristics are also investigated. This work suggests an alternative way to achieve the broadband electromagnetic transparency and has great guiding significance for the practical fabrication of ETD.