Electromagnetic shielding effectiveness of carbon fibre reinforced composites

This paper reports results on the shielding effectiveness parameter of laminated epoxy composites with carbon fibre reinforcements. Measurements of shielding effectiveness were carried out with a coaxial transmission line testing chamber according to ASTM 4935 standard and epoxy-matrix composites with continuous carbon-fibres were proven to be an excellent electromagnetic interference shielding material, where a composite slab made of 4 layers of prepregs provided more than 99.9% of electromagnetic attenuation. It was found that the reflection mechanism of the shielding material was mainly influenced by the fibre volume ratio, and that an increase in the number of layers of the composite resulted in higher shielding effectiveness due to a greater absorption mechanism. Calculations of the shielding effectiveness parameter of the material used were made by means of commercial electromagnetic simulation tools, having determined experimentally the overall resistivity of the composite. The findings presented in this work suggest that in presence of a greater number of interfaces at different impedance the separate modelling of matrix and fibres at mesoscopic scale must be taken into account

Development and evaluation of the elastic recovery concept for expandable space structures

Elastic recovery of expandable space structure

AN ANALYSIS OF SIZE, WEIGHT AND POWER (SWAP) FOR EMP SHIELDING OF THE RAAD SYSTEM

In 2019, the U.S. Army’s Future Study Program designed and led the Unified Quest Multinational Seminar Wargame. This wargame examined U.S. forces, partners, and allies’ interoperability requirements to defeat a near-peer threat in a future operational environment. As part of the seminar wargame, Army forces executed a critical air assault operation in adversary-controlled terrain to support a river crossing. This task covers multiple aspects of operational planning and coordination for an assault operation as outlined in AFC Pamphlet 71 20-1. An air assault execution revealed the challenges of performing a complex forcible entry operation in a contested, anti-access/aerial denial (A2/AD) environment. Even with future aircraft, the air assault operation was vulnerable to enemy air defense capabilities. Landing zone restrictions reduce the number of areas the multinational forces could conduct air assault operations, providing a marked advantage to near-peer adversaries in planning likely counterattack operations and increasing the risk to forces. Through a combination of integrated air defense systems (IADS), indirect fires, direct fires, and reserve formations specifically tasked with contesting air assault operations, threat forces are expected to contest the air assault force during insertion. As the report stated, the wargame demonstrated the need for new Army air assault capabilities.Major, United States ArmyMajor, United States ArmyCaptain, United States ArmyMajor, United States ArmyMajor, United States ArmyApproved for public release. Distribution is unlimited

Electromagnetic Properties of Multifunctional Composites Based on Glass Fiber Prepreg and Ni/Carbon Fiber Veil

Multifunctional composites combine structural and other physicochemical properties, with major applications in aeronautical, space, telecommunication, automotive, and medical areas. This research evaluates electromagnetic properties of multifunctional composites based on glass fiber woven fabric pre-impregnated with epoxy resin laminated together carbon fiber non-woven veil metalized with Ni. In this way, searching for possible application as radar absorbing structures or electromagnetic interference shielding structures. The scattering parameters, in the frequency range of 8.2 to 12.4 GHz, show that the epoxy resin/glass fiber prepreg allows the transmission of the electromagnetic waves through its microstructure, independently of the glass fiber reinforcement orientation (98% transmission, S-24 = -0.09 dB). However, the carbon fiber/Ni veil shows highly reflector behavior (91% reflection, S-22 = -0.43 dB). Energy dispersive spectroscopy of the veil, before and after nitric acid attacks, confirmed the Ni coating removal from the carbon fiber surface. Still, the scattering parameters show reflector behavior (77% reflection, S-22 = -1.13 dB), attributed to the electrical conductivity of carbon fibers. Multifunctional composites based on glass fiber/epoxy/carbon fiber/Ni veil laminates were processed by hot compression molding. The scattering parameters show that the laminates do not behave as good radar absorbing structures. Nevertheless, the laminates present promising results for application as light weight and low thickness structural composites with electromagnetic interference shielding effectiveness (91.4% reflection for 0.36 mm thickness and 100% for similar to 1.1 mm) for buildings, aircraft, and space components.Univ Estadual Paulista, Fac Engn Guaratingueta, Dept Mat & Tecnol, Ave Dr Ariberto Pereira Cunha,333 Portal das Coli, BR-12516410 Guaratingueta, SP, BrazilInst Technol Aeronaut, Dept Ciencia & Tecnol Aeroespacial, Lab Guerra Elect, Sao Jose Dos Campos, SP, BrazilUniv Fed Sao Paulo, Inst Ciencia & Tecnol Curso Engn Mat, Sao Jose Dos Campos, SP, BrazilUniv Fed Sao Paulo, Inst Ciencia & Tecnol Curso Engn Mat, Sao Jose Dos Campos, SP, BrazilWeb of Scienc

Lightweight and highly conductive silver nanoparticles functionalized meta-aramid nonwoven fabric for enhanced electromagnetic interference shielding

High-performance electromagnetic interference (EMI) shielding material that that can function properly under extreme working conditions is critical for their practical applications. Herein, flexible and highly conductive meta-aramid (PMIA) nonwoven fabrics were fabricated by combining polydopamine (PDA) modification and electroless silver plating. The PDA modification greatly enhanced the efficient deposition of silver nanoparticles (AgNPs) and the interfacial cohesion between the AgNPs and the PMIA fibers. The silver-coated PMIA nonwoven fabric exhibited an electrical conductivity as high as 0.29 Ω/sq, an excellent EMI shielding effectiveness (SE) of 92.6 dB and a high absolute EMI SE of 8194.7 dB cm^{2} g^{−1}. In addition, the silver-coated PMIA nonwoven fabric maintained high electrical conductivity and EMI SE after being subjected to washing, bending and torsion deformations, high/low temperature, strong acidic/alkaline solutions and different organic solvents. These results have clearly demonstrated that PMIA nonwoven fabric can be made highly electrically conductive by using a simple and highly scalable method. It holds great promise for the applications in EMI shielding materials that can be used in various harsh conditions

Composites Made of Polypropylene Nonwoven Fabric with Plasmas Layers

Engineering of materials used for shielding from electromagnetic fields is currently one of the most extensively developing field of applications of composite materials (Bula et al., 2006; Jaroszewski & Ziaja, 2010; Koprowska et al., 2004, 2008; Sarto et al. 2003, 2005; Wei et al., 2006; Ziaja et al., 2008, 2009, 2010). The choice of suitable materials for the shields and their appropriate arrangement have an essential meaning. Development of lightweight and resistant to environmental exposure shielding materials is possible by using substrates of polypropylene and plasma technology (Ziaja&Jaroszewski, 2011). The shields for suppression of electric field were made in the form of composites of polypropylene unwoven fabrics with deposited plasma layers. Additional advantage of the application of the method is the possibility of plasma cleaning of a fabric surface and modifying its surface properties. The unique properties of pulse plasma make possible to obtain metallic and dielectric coatings on polypropylene fabrics, which are not achievable by standard methods. The coatings are characterized by a good adhesion to the substrates. The surface of the samples was examined in two ways: by metallurgical microscope Nikon MA200 and scanning microscope Quanta 200 in the low vacuum mode. To identify the structure of the obtained layers the X-Ray radiography was used. Additionally properties of the composites was studied using impedance spectroscopy. The method of impedance spectroscopy allows one to connect the measured frequency characteristics with the physical structure of tested material and the alternations in the structure. This method has been used by the authors to determine the properties of plasma layers deposited on a polypropylene nonwoven fabric (Jaroszewski et al., 2010a; Pospieszna et al., 2010; Pospieszna et al., 2010b)

Textile materials

In this specialised publication, the reader will find research results and real engineering developments in the field of modern technical textiles. Modern technical textile materials, ranging from ordinary reinforcing fabrics in the construction and production of modern composite materials to specialised textile materials in the composition of electronics, sensors and other intelligent devices, play an important role in many areas of human technical activity. The use of specialized textiles, for example, in medicine makes it possible to achieve important results in diagnostics, prosthetics, surgical practice and the practice of using specialized fabrics at the health recovery stage. The use of reinforcing fabrics in construction can significantly improve the mechanical properties of concrete and various plaster mixtures, which increases the reliability and durability of various structures and buildings in general. In mechanical engineering, the use of composite materials reinforced with special textiles can simultaneously reduce weight and improve the mechanical properties of machine parts. Fabric- reinforced composites occupy a significant place in the automotive industry, aerospace engineering, and shipbuilding. Here, the mechanical reliability and thermal resistance of the body material of the product, along with its low weight, are very relevant. The presented edition will be useful and interesting for engineers and researchers whose activities are related to the design, production and application of various technical textile materials

Influence of Metal Fiber Content and Arrangement on Shielding Effectiveness for Blended Electromagnetic Shielding Fabric

More metal fiber content of blended electromagnetic shielding (EMS) fabric results in higher shielding effectiveness (SE) of the fabric. However, there is little information about the influence of the metal fiber content on the SE considering the fabric structure. This study constructs an index of metal fiber content per unit area (MFCPUA), and discusses the influence of the metal fiber content on the SE of the EMS fabric when fabric parameters are changed. Computations for the MFCPUA and the thickness and porosity of the metal fiber arrangement are given, and then experiments are designed to test the SE of different EMS fabric samples. According to the experimental results, the influence of the MFCPUA on the SE is analyzed and influence mechanism is discussed when the fabric weaves, emission frequencies and weft and warp densities are changed. Results show that the MFCPUA and the SE are positive increase relation; the frequency and the SE are the negative increase relation when the metal fiber content is unchanged; the influence of the fabric weave type on the SE depends on the length of the yarn floats; the SE values of fabric with same weave are same when the MFCPUA is same regardless of the fabric density.DOI: http://dx.doi.org/10.5755/j01.ms.21.2.6529</p