IndexAbstractIntroductionFabrication of ras laminatesElectromagnetic characterization of ras laminatesElectromagnetic design of ras compositesConclusionAbstractThe work proposed in this paper describes the electromagnetic design, simulation and fabrication of a radar absorbent structural composite (RAS) multilayer carbon based materials for X-band applications. The RAS laminates were fabricated using the lossy carbon materials in the epoxy matrix together with glass fabrics as load-bearing elements. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get Original Essay Initially various RAS laminates were fabricated using the vacuum bag technique and characterized for its permittivity and loss tangent values. Furthermore, based on electromagnetic design and optimization, the classified laminates were stacked for the final optimized configuration of RAS composites. The developed RAS was characterized for electromagnetic properties using free space measurement system and shows a minimum reflection loss of 10 dB in the X-band frequency region. The fabricated composite exhibits remarkable mechanical properties and shows its potential application for stealth radar applications. Introduction Stealth technology, including radar cross-section (RCS) reduction, has become essential in the era of electronic warfare. RCS reduction can be achieved by modeling aircraft, using Radar Absorbent Materials (RAM) coatings and Radar Absorbent Structures (RAS). Aircraft modeling includes designing the external features of the aircraft to reduce the reflection of electromagnetic (EM) waves in the RADAR direction. RAM and RAS are developed with the aim of absorbing electromagnetic radiation and thus minimizing reflected waves. Aircraft modeling has its limitations because it can interfere with the external profiles established by aircraft designers to meet aerodynamic requirements. Therefore, RAM and RAS developments have become essential for reducing RCS. RAMs are generally manufactured in the form of sheets consisting of insulating polymer as matrix material and filler materials with magnetic or dielectric losses. RAMs are easily applied to the surfaces of existing structures but increase structural weight and have poor mechanical and environmental resistance properties. Therefore, RAMs are not self-contained materials and cannot be used as load-bearing structures. They also require constant maintenance and repair. RAS consists of fiber-reinforced composites and leaky materials that are dispersed into the composite matrix. The radar absorption efficiency of RAS is achieved by materials that provide special absorption properties and structural characteristics such as the stacking sequence of the composite layers. The stacking characteristics of composites facilitate multilayer structures, which are necessary to broaden the bandwidth of reflection loss. For a lossy filler to be highly effective, it should have high conductivity for wave attenuation, a high aspect ratio to form a conductive network, and a small size relative to the depth of the skin. The absorption and reflection characteristics of a RAS depend on a number of variables, which include the frequency, angle of incidence, and polarization of the EM wave, and the permittivity, permeability, and thickness of each layer of the RAS. In this study, the RAS for the X-band frequency regionwas designed and developed using porous carbon black and carbon fibers as radar absorbing materials and glass/carbon fabric as reinforcement in the epoxy medium. The RAS was developed by stacking the four different layers using the vacuum bag molding technique and characterized for their mechanical and electromagnetic properties in the X-band frequency region using a free space measurement system. The layer stacking sequence for this RAS was derived by performing simulation studies using the layer properties, i.e. effective permittivity and thickness. To determine the effective permittivity of a single layer, it was fabricated separately and was evaluated using the free space measurement system. Fabrication of ras laminates The matrix system used for the fabrication of the composites was Araldite 5052 (epoxy resin) and Aradur 5052 (hardener) from Huntsman advanced materials Pvt Ltd. This is a cold curing epoxy system with low viscosity (1000 – 1500 mPaS for Araldite 5052 and 40 – 60 mPaS for Aradur 5052 at 250°C) and long pot life (2 hours per 100 ml at room temperature). The mixing ratio of epoxy resin to hardener was 100:38 parts by weight. The 300 g/m² E-glass 8H satin weave fabric was selected as reinforcement. First, the four individual layers of RAS were fabricated by varying the concentration of fillers in a defined order (Table 1). Since the filler materials used in this study are conductive, their proportion in the resin system and the stacking sequence of these layers is extremely critical for the fabrication of efficient RAS. First, the absorbent fillers were mixed with the matrix system until a uniform dispersion of each filler material was obtained. Then, the modified matrix material was applied on the reinforcement layers by wet layering method. Finally, individual layers of RAS were fabricated using the vacuum bag molding technique. 5x 6yElectromagnetic characterization of ras laminatesThe Free Space Measurement System (FSMS) from HVS Technologies, Pennsylvania State, USA together with the Vector Network Analyzer PNA E8364B from Agilent Technologies, USA was used for the measurement of complex permittivity and reflection loss of RAS stacks and final RAS composites in the X-band frequency region. The FSMS consists of a pair of spot-focused horn lens antennas to provide focused plane-wave illumination to the sample measurement plane. The FSMS was calibrated using the Thru-Reflect-Line (TRL) calibration technique with time-domain gating. The variation of dielectric constant and loss tangent of the composite stacks with frequency in the X-band frequency region, can be clearly observed from the graph that the permittivity values ​​continues to increase in increasing order from stack1 to stack4. Stack "4" has the highest true permittivity value (14.82-12.32) and has a higher concentration of lossy ingredients which results in a loss tangent value ranging from 3.20-3, 15 while the RAS stack “1” has the lowest value of true permittivity (4.94- 4.99) and a loss tangent value that varies from .04-0.01Electromagnetic design of ras compositesAn electromagnetic traveling along the positive Z direction affects RAS stacks normally, which results in a series of waves traveling along the positive direction and reflected waves traveling along the negative Z direction. Let ti,ηi and denote the thickness, complex intrinsic impedance and constant respectively of propagation of the i-th layer (i=1,2,3………n), , are the.