Elsevier

Composite Structures

Volume 273, 1 October 2021, 114256
Composite Structures

Mechanical and electromagnetic behavior of fabricated hybrid composite sandwich radome with a new optimized frequency-selective surface

https://doi.org/10.1016/j.compstruct.2021.114256Get rights and content

Highlights

  • A multi-criteria decision-making design procedure to fabricate hybrid sandwich radome.

  • Three-point bending and impact tests to examine the mechanical performance of radome.

  • The genetic algorithm together with the CST software to design and optimize FSS.

  • Water absorption test to investigate the environmental resistance of sandwich radome.

  • Achieving the maximum transmission at the any desired resonance frequencies.

Abstract

A multidisciplinary design procedure was presented to fabricate hybrid composite sandwich (HCS) panels used in radomes based on conducting several mechanical and electromagnetic experiments. Accordingly, six specimens made of E-glass/aramid/polyester face sheets with different stacking sequences and polyvinyl chloride foam core were prepared using the vacuum-assisted resin transfer molding process. Afterward, three-point bending and low-velocity impact tests were performed and several mechanical characteristics were reported for specimens. Besides, electromagnetic wave transmission performance of the HCSs was experimentally and numerically determined. The accuracy of the simulated results was confirmed by free-space measurement method.

The most efficient design of the hybrid stacking sequence was subsequently found by implementing the complex proportional assessment method and considering the mechanical and electromagnetic characteristics together with the moisture resistance of the specimens. Eventually, a new embedded frequency-selective surface (FSS) was designed for the radome using a genetic algorithm to maintain the transmission rate in the desired band at the order of higher than 90 percent. The comparison of the new FSS performance with conventional FSSs in the literature exhibited that the present optimization procedure not only achieves the maximum transmission at the resonance frequency but also enhances the transmission loss outside of the desired frequency band.

Introduction

Nowadays, antennas are used for predicting the weather, monitoring climate changes, managing ground, air, and sea transportation [1], [2], [3], [4], but they are very susceptible to environmental conditions such as rain erosion, lightning strike, ultraviolet rays, sand, and wind. In this regard, the radome is a protecting cover that has been utilized in the antennas to resolve these weaknesses [5], [6], [7]. Since composite materials reveal outstanding physical and mechanical properties over metallic parts in different environmental conditions, the laminated composite plates/shells were proposed to protect radars. However, the laminated composites are susceptible to damage which can be induced by out-of-plane mechanical loadings such as impact and bending conditions [8]. To overcome the mentioned limitations, the sandwich composite structures have been recently utilized in the fabrication of radar components such as radome due to their higher transverse stiffness, high absorption energy, and, lightweight as well as better electromagnetic (EM) wave transmission performance [9], [10], [11], [12].

Among different radomes, the ones possessing superiority of stealth characteristics, are named low-observable radomes (LORs). Meanwhile, the design of composite radomes composed of FSSs is crucial to satisfy two main goals of preventing coupling between nearby transmitter antennas and also reducing radar cross-section [13]. Besides, it performs as a filter to reduce the transmission rate of EM waves which are out of desired bandwidth. Consequently, the optimization of FSS geometry is also an important design factor besides the aforementioned mechanical constraints.

With the wide deployment of composite sandwich structures, much attention has been devoted to study the mechanical behavior of these materials. Focusing on the radome structures, performing experimental tests, or developing numerical/analytical models to examine the flexural stiffness and impact behavior of such elements is much important [14], [15], [16], [17]. The related researches revealed that the shear and tensile properties of sandwich composite beams can be controlled by choosing various types of fibers, resins, and cores. The main damage modes of the sandwich structures subjected to the bending moments and shear loads were reported as the core shear failure, fiber micro-buckling, indentation, and face wrinkling [18], [19], [20]. In this regard, Birman et al. [11] provided a comprehensive review of the experimental procedures as well as the analytical, and numerical methods for sandwich composites under mechanical loadings. Wang et al. [21], [22] investigated the numerical and experimental bending performance of the sandwich composites with ceramic face and honeycomb core under the three-point bending loading condition. Besides the studies concerning the static behavior of composite structures, many investigations have been dealt with the dynamic behavior analysis of these advanced materials [23], [24], [25], [26]. Furthermore, many studies have been examined the low-velocity impact response of stitched composites and conventional sandwich structures [27], [28], [29], [30], [31]. However, no additional information concerning the EM properties of the stitched composites has been provided. The results of the researches showed that the absorbed energy and impact resistance of the composites can be improved by adding fibers in the transverse direction. Evaluation of the sandwich structures response under oblique impact is another subject of interest to investigate the effect of this type of loading on the impact force, impactor maximum displacement, absorbed energy, and damaged area [32], [33].

Due to the multidisciplinary nature of the subject under consideration, it is crucial to assess the EM performance of the composite structures. In this respect, Dasgupta [34] reported certain important EM properties of the composites commonly used in aircraft and radome structures. To evaluate the electromagnetic transmission (EMT) characteristics of the LORs discussed in the article, the free-space measurement system was employed to determine the parameters such as transmission loss, resonant frequency, and transmission bandwidth for different fiber-reinforced polymer composite radomes [35], [36], [37], [38], [39].

Choi et al. [40] used E-glass/aramid/epoxy hybrid composites to fabricate a new low-observable radome with FSS. For this structure, the EM wave transmission performance was determined by numerical simulations and evaluated via a free-space measurement method. Besides, mechanical behavior was studied using a three-point bending test. Xu et al. [41] employed a coupled dielectric-mechanical testing method based on the mechanical experiments and free-space method to show the capabilities of aramid/epoxy composites for wave-transmitting components. Zhou et al. [42] presented an efficient method based on the small reflections theory to design dual/multi-band radome walls. They validated the analytical predictions with the experimental measurements. Ilavarasu et al. [43] compared different methods of the radome design considering different parameters such as EM properties, material selection, various load cases like impact loading, and some aspects of the fabrication. Further researches have been dealt with different aspects of embedding FSSs in the radome structures [44], [45], [46], [47]. On this subject, to optimize the geometry pattern of the FSSs, the efficacy of several optimization algorithms including the particle swarm optimization algorithm [48], [49], genetic algorithm [50], [51], and other conventional algorithms [52], [53], [54] was examined. For instance, Ohira et al. [55] presented an intelligent method to optimize the configurations of the FSSs and showed that there is a good agreement between the measured and calculated transmitted EM waves of the introduced FSSs. It is noticeable that the LORs made from sandwich composites need to simultaneously satisfy the mechanical and EM requirements.

As discussed, the radomes shall exhibit mechanical, electromagnetic and environmental performances simultaneously. While several investigations have been performed by separately studying the aforementioned design factors, there is only limited literature concerning development of a multipurpose design of radomes. Here, for the first time, the mechanical, EM and environmental characteristics of HCS LORs were primarily examined by conducting three-point bending test, low-velocity impact experiment, free space measurements as well as moisture absorption test, then the best configuration of the HCS components was chosen by implementing the modified digital logic (MDL) and complex proportional assessment (COPRAS). This work can provide a benchmark design for composite LORs by appropriately selecting the stacking sequence and face thickness of the initial specimens, employing a modern fabrication method of composites, performing mechanical and EM experiments, and eventually finding the best layout of the radome structure using a multi-criteria decision-making method. In addition, a new design of FSS embedded in the radome structure was introduced by employing the powerful optimization technique of genetic algorithm to obtain a maximum transmission rate.

Section snippets

Materials and experimental methods

In this part, the fabrication process of the HCS specimens was described. Also, the performed mechanical, environmental, and EM tests including drop-weight impact, three-point bending, water absorption, and free-space tests were explained. The shape of the structure under consideration was schematically shown in Fig. 1.

The assessment of the flexural properties, impact resistance and transmission loss parameters in the sandwich composite is necessary to design the LORs as they are susceptible to

Flexural properties

The load–displacement histories were extracted from the three-point bending tests according to the ASTM D7250/D7250M-06 [57], D7249/D7249M-6 [58], and C 393/C 393M-06 [59] standards for the six specimens. The specimens’ dimensions were selected such that the geometry requirements of the above standards were satisfied. The specific force, maximum beam deflection, facing stress, and core ultimate shear strength parameters were used here to compare the mechanical performance of the sandwich

Selection of HCS radome

In this section, the complex proportional assessment is used to select the best sample for LOR application considering the mechanical and electromagnetic characteristics together with the moisture resistance properties of the HCS specimens. According to the developed experimental results, seven criteria were selected for the final assessment of the specimens as summarized in Table 5.

Among these, the facing ultimate stress of the bending test, the impact force peak value and damage threshold

Design and optimization of FSSs

Many periodic configurations like dipoles, cross dipoles, tripoles, rings, and square loops have been used as FSS elements in several previous works [75]. Fig. 15 schematically shows the stages of procedure by which the FSS was fabricated by using chemical etching process on the sandwich radome. (a) A 20 µm thick copper foil was bonded on the face of sandwich radome with an epoxy adhesive (Araldite® 2011, USA). (b) A thin layer of UV-sensitive photoresist was coated on the copper film using

Conclusions

The purpose of this paper was to design LORs consisting of HCSs and, also, benchmark a method for optimizing the geometry of the FSSs embedded in the structure. Initially, the dielectric constant and loss tangent characteristics of the components were calculated to select the permissible configuration for the HCS made of aramid and glass fibers. Then, the radome mechanical performance was examined by performing three-point bending and low-velocity impact tests on fabricated specimens with

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References (77)

  • L. Zhou et al.

    Design and characterization for a high-temperature dual-band radome wall structure for airborne applications

    Mater Des

    (2017)
  • M. Wahab

    Radar radome and its design considerations. International Conference on Instrumentation

    Communication, Information Technology, and Biomedical Engineering

    (2009)
  • D.J. Kozakoff

    Analysis of radome-enclosed antennas

    Artech House

    (2010)
  • S. Lin et al.

    Fabrication of multilayer electronic magnetic window material by Si2N2O decomposition

    Mater Des

    (2016)
  • C. Li et al.

    The use of cutting carbon fiber fabric/epoxy composites as band-pass frequency selective surfaces

    J Compos Mater

    (2014)
  • Mani G. Radome Materials. Microwave Materials: Springer; 1994. p....
  • F. Costa et al.

    A frequency selective radome with wideband absorbing properties

    IEEE Trans Antennas Propag

    (2012)
  • B. Kazemianfar et al.

    Response of 3D woven composites under low velocity impact with different impactor geometries

    Aerosp Sci Technol

    (2020)
  • Chai GB, Zhu S. A review of low-velocity impact on sandwich structures. Proceedings of the Institution of Mechanical...
  • C. Hwu et al.

    Free vibration of composite sandwich plates and cylindrical shells

    Compos Struct

    (2017)
  • Birman V, Kardomatea GA. Review of current trends in research and applications of sandwich structures. Composites Part...
  • Meola C, Boccardi S, Carlomagno Gm. Chapter 1 - Composite materials in the aeronautical industry. Infrared Thermography...
  • J.-C. Zhang et al.

    Design of narrow band-pass frequency selective surfaces for millimeter wave applications

    Prog Electromagn Res.

    (2009)
  • Toygar ME, Tee KF, Maleki FK, Balaban AC. Experimental, analytical and numerical study of mechanical properties and...
  • F. Bourouis et al.

    Comparative study and optimization of the mechanical behavior of sandwich beams loaded in three point bending

    J Build Mater Struct

    (2018)
  • P. Paczos et al.

    Three-point bending of sandwich beam with special structure of the core

    Compos Struct

    (2018)
  • A. Karamanlı

    Bending analysis of composite and sandwich beams using Ritz method

    Anadolu Üniversitesi Bilim Ve Teknoloji Dergisi A-Uygulamalı Bilimler ve Mühendislik.

    (2018)
  • I.M. Daniel et al.

    Failure modes of composite sandwich beams

    Int J Damage Mech

    (2002)
  • C.A. Steeves et al.

    Collapse mechanisms of sandwich beams with composite faces and a foam core, loaded in three-point bending. Part I: analytical models and minimum weight design

    Int J Mech Sci

    (2004)
  • V. Birman et al.

    Review of current trends in research and applications of sandwich structures

    Compos B Eng

    (2018)
  • Z. Wang et al.

    Experimental investigation on bending behavior of honeycomb sandwich panel with ceramic tile face-sheet

    Compos B Eng

    (2019)
  • Z. Wang et al.

    Numerical study on three-point bending behavior of honeycomb sandwich with ceramic tile

    Compos B Eng

    (2019)
  • A.R. Setoodeh et al.

    Low velocity impact analysis of laminated composite plates using a 3D elasticity based layerwise FEM

    Mater Des

    (2009)
  • A. Kavianiboroujeni et al.

    Low velocity impact behaviour of asymmetric three-layer sandwich composite structures with and without foam core

    Polym Polym Compos

    (2017)
  • J. Zhou et al.

    The low velocity impact response of foam-based sandwich panels

    Compos Sci Technol

    (2012)
  • M. Elamin et al.

    Impact damage of composite sandwich structures in arctic condition

    Compos Struct

    (2018)
  • M. Esmaeeli et al.

    Simultaneous optimization of elastic constants of laminated composites using artificial bee colony algorithm

    Adv Compos Hybrid Mater

    (2019)
  • M. Esmaeeli et al.

    Geometric analysis and constrained optimization of woven z-pinned composites for maximization of elastic properties

    Compos Struct

    (2019)
  • B. Kazemianfar et al.

    Experimental investigation on response and failure modes of 2D and 3D woven composites under low velocity impact

    J Mater Sci

    (2020)
  • S. Samlal et al.

    Effect of stitching angle on impact characteristics of sandwich panels

    Int J Innov Res Sci Eng Technol

    (2015)
  • R. Santhanakrishnan et al.

    Impact study on sandwich panels with and without stitching

    Adv Compos Mater

    (2018)
  • Chen Y, Han X, Hou S, Fu K, Ye L. A numerical study of a composite sandwich panel under oblique impact. 21th...
  • I. Iváñez et al.

    The oblique impact response of composite sandwich plates

    Compos Struct

    (2015)
  • S. Dasgupta

    Polymer matrix composites for electromagnetic applications in aircraft structures

    J Indian Inst Sci

    (2015)
  • P.C. Kim et al.

    EM characteristics of the RAS composed of E-glass/epoxy composite and single dipole FSS element

    Compos Struct

    (2006)
  • P.C. Kim et al.

    Low-observable radomes composed of composite sandwich constructions and frequency selective surfaces

    Compos Sci Technol

    (2008)
  • I. Choi et al.

    Aramid/epoxy composites sandwich structures for low-observable radomes

    Compos Sci Technol

    (2011)
  • H. Li et al.

    Design and realization of a high transmission x-band radome for low-speed flight platform

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