Survivability Of Aircraft Research Articles

Dielectric properties and temperature dependence of holey graphene/resin composites

In order to enhance the survivability of fighter aircraft, it is crucial to develop microwave absorbing (MA) materials with a low dielectric-temperature dependence. Reduced graphene oxide (RGO) has potential for military stealth applications, but its wave absorbing properties are highly sensitive to temperature fluctuations due to significant conductivity loss. In this work, conductivity and polarization loss are balanced through microstructural design to disrupt the conductive pathways by creating holes on the graphene surface. The holey RGO aerogel/phenolic resin (HRGA/PF) composites with a hierarchical pore structure were synthesized through combining freeze-drying and PF infiltration. The results show that the HRGA/PF composites possess excellent X-band full frequency absorption performance in the temperature range of 25 °C–250 °C, and the reflection loss (RL) is optimized to −62.78 dB. This work expands feasible thoughts for the design of stable MA materials with wide temperature range.

Ingeniously construction of industrial carbon fiber/nickel-iron layered double hydroxide heterostructure composite for high-efficient microwave absorption in aircraft

To enhance the survivability of military aircraft in electromagnetic warfare, carbon fiber/nickel-iron layered double hydroxide (CF/NiFe-LDH) composites with heterogeneous structure were constructed starting from the raw industrial carbon fiber (CF) by electrostatic self-assembly. By reasonably adjusting the mass ratio of CF and NiFe-LDH, the voids formed by LDH arrays stacked on the fiber surface are utilized to promote reflection and scattering of electromagnetic wave (EMW), optimizing impedance matching, as well as synergize dielectric-magnetic dual loss mechanism. Moreover, interfacial polarization effect induced by the abundant heterogeneous interfaces significantly enhance the ability of EMW dissipation. The optimized CF/NiFe-LDH heterostructure composite exhibits the minimum reflection loss (RLmin) value of −52.48 dB at mere 1.77 mm thickness and an expansive maximum effective bandwidth (EABmax) of 7.29 GHz at 2.14 mm. In addition, the computer simulation technology (CST) revealed that the radar scattering cross section (RCS) reduction of composites reaches up to 26.92 dBm2 at an incidence angle of 90°, demonstrating their excellent radar attenuation capability. Tremendously, the heterogeneous composites achieve an SRL1 value of 524.8, which is appreciably better than most of the EMW absorbing materials. The wondrous characteristics including lightweight, ultra-thin, high-efficient microwave absorbing ability of CF/NiFe-LDH heterostructure composites display potential application in fighter aircraft.

High temperature flexible 2D metasurface based on optimal design for thermal insulation and electromagnetic wave absorption skin

The development of radar stealth skin with long term stable service and flexible deformability is the premise and foundation of improving the battlefield survivability of deformable aircraft. Aiming at the bottleneck problem of mismatch between the flexible configuration and the electromagnetic configuration of the existing stealth composite materials, a new type of SiO2 fiber paper (SFP) with flame retardant, thermal insulation, low dielectric constant and super-hydrophobic was prepared by combining the papermaking process with surface modification. The effects of solid content and high temperature environment on the mechanical properties, thermal insulation properties, dielectric properties and hydrophobic properties of SFP materials were studied in detail. Based on this, the optimal design and construction method of radar stealth metasurface suitable for flexible deformation are proposed, and the high temperature resistant flexible stealth skin metasurface is obtained. The metasurface has been demonstrated to achieve an effective wave absorption of −8 dB in the 10.9–16.4 GHz range at 400 μm thickness, making it an ideal candidate for flame retardant, flexible, thermal insulation and radar stealth skin under extreme conditions. It provides theoretical basis and technical support for the innovative development of high-speed deformable stealth aircraft.

Numerical Study on Infrared Radiation Characteristics of Stealth Coating for Turbofan Engine Tail Nozzle

Infrared stealth technology plays a vital role in improving the survivability of future aircraft. The exhaust system is the main source of infrared radiation on the rear side of the aircraft, and stealth coating is an effective measure to reduce the infrared radiation on the solid wall of the nozzle. Mature commercial computational fluid dynamics software was used to obtain and analyze accurate data of the flow field to study the infrared radiation characteristics of the stealth coating on the turbofan engine nozzle. Furthermore, infrared simulation software based on the reverse Monte Carlo method, line-by-line calculation technique, and database technology for high-temperature gas parameters of a narrowband model were used to numerically simulate the exhaust system of a turbofan engine with infrared suppression coating. Assuming that the damage percentage of the external adjusting plate is constant, the findings reveal that the overall infrared radiation intensity exhibits a steadily increasing trend with the increase in the number of damaged adjusting plates. The maximum change in the infrared radiation intensity between eight damaged adjusting plates and one damaged adjusting plate was 11.67%. Thus, regular inspection and maintenance are required for the stealth coating on the external adjusting plate of the aero-engine tail nozzle to maintain stealth integrity.

고체/액체 혼합 입자 분사에 의한 항공기 노즐의 다상 유동에 관한 전산 해석

Infrared (IR) signals from the hot exhaust gases of aircraft engines have a significant impact on the survivability of aircraft. Several methods were developed to reduce IR signatures to avoid tracking by IR signatures generated in the exhaust, or decoy flares are used to deceive IR seekers. Research into injecting water particles to lower the exhaust gas temperature or injecting carbon particles to shield the plume has also been previously conducted. In this study, we propose a method for injecting solid/liquid mixed particles that lower the exhaust gas temperature and block IR signal propagation generated in the exhaust gas. The multiphase flow in aircraft nozzles by solid/liquid mixed particle injection was analyzed using the CFD code for the total flow rate of particles corresponding to 5%, 10%, and 20% of the exhaust gas flow rate. After analyzing the characteristics of the mixed particles interacting with the exhaust plume, the optimal flow rate of water and carbon particles with a small thrust penalty was obtained.

Selective thermal emission and infrared camouflage based on layered media

Infrared camouflage based on artificial thermal metasurfaces has recently attracted significant attention. By eliminating thermal radiation differences between the object and the background, it is possible to hide a given object from infrared detection. Infrared camouflage is an important element that increases the survivability of aircraft and missiles, by reducing target susceptibility to infrared guided threats. Herein, a simple and practicable design is theoretically presented based on a multilayer film for infrared stealth, with distinctive advantages of scalability, flexible fabrication, and structural simplicity. The multilayer medium consists of silicon substrate, carbon layer and zinc sulfide film, the optical properties of which are determined by transfer matrix method. By locally changing the thickness of the coating film, the spatial tunability and continuity in thermal emission are demonstrated. A continuous change of emissive power is further obtained and consequently implemented to achieve thermal camouflage functionality. In addition, other functionalities, like thermal illusion and thermal coding, are demonstrated by thickness-engineered multilayer films.

IR Susceptibility of Supersonic Aircraft according to Omni-directional Detection Angle

Infrared guided weapons act as threats that greatly degrade the survivability of combat aircraft. Infrared weapons detect and track the target aircraft by sensing the infrared signature radiated from the aircraft fuselage. Therefore, in this study, we analyzed the infrared signature and susceptibility of supersonic aircraft according to omni-directional detection angle. Through the numerical analysis, we derived the surface temperature distribution of fuselage and omni-directional infrared signature. Then, we calculated the detection range according to detection angle in consideration of IR sensor’s parameters. Using in-house code, the lethal range was calculated by considering the relative velocity between aircraft and IR missile. As a result, the elevational susceptibility is larger than the azimuthal susceptibility, and it means that the aircraft can be attacked in wider area at the elevational situation.

On the low- and high-velocity impact behaviour of hybrid composite materials at room and extreme temperature

A demand raised is how to improve the survivability of aircraft and naval structures concerning low- and high-velocity impacts. Since fundamental failure is due to mainly by fracture, a fundamental understanding of both mechanisms and mechanics of the material is crucial. It is important to understand the deformation and damage mechanisms involved in the impact to improve the design of composite structures. Several approaches have been exploited to improve the impact damage resistance of composite laminates in different conditions. Among these, the development of composite laminates stacking different fibres in the same matrix results very interestingly. This paper deals to investigate on the high and low speed impact performance of hybrid composite configurations made of glass/carbon and basalt fibres. Low-velocity impact at penetration and high speed tests at different impact velocity were carried out at the room and low temperatures to evaluate the goodness of hybridization proposed and the temperature effect on the composite performances. Among the three proposals, a hybrid basalt carbon configuration was identified as the best both at low speeds and at high impact speeds for both temperatures tested.

Research review on design method of ice protection system for civil aircraft based on ice-tolerant concept

Icing is an important disaster-causing factor which threatens the flight safety of civil aircraft and a major safety issue of concern for the airworthiness. The design of icing protection system based on ice-tolerant concept can minimize the impact of icing on aerodynamic characteristics and fully utilize the potential of flight performance, which is the frontier direction of current icing protection research for civil aircraft. This paper aims at the requirements of civil aircraft flight safety design and airworthiness certification. The design method of civil aircraft icing protection system based on the concept of ice-tolerant capacity is analyzed from two aspects. One is the capacity of ice-tolerant for aircraft frame, the other one is the design of ice-tolerant with active control. The optimum design strategy of wing in aerodynamic performance considering icing loss is refined and the design idea of ice-tolerant protection control system based on flight control law reconstruction is formed. The change from passive flight safety of icing to active safety design of icing can effectively improve the survivability and safety of civil aircraft under icing weather conditions.

Numerical Analysis of Structural Soundness by Sloshing Movement in an External Fuel Tank for Rotorcraft

Fuel sloshing during rapid maneuvers of an aircraft causes significant loads on internal components, which in severe circumstances may break components or pipes and cause fuel to leak out of the fuel tank. Moreover, a significant load is applied to the joints of an external fuel tank by such sloshing movements. This may affect the survivability of the crew as well as the safety of the aircraft, when the joints of the external fuel tank are damaged due to a design that does not accommodate the sloshing load. Therefore, to improve the survivability of aircraft and crew members, the design of external fuel tanks should be performed after estimating the structural soundness for the sloshing load through a numerical analysis of the fuel sloshing conditions. In this study, numerical analysis was performed for a sloshing test of an external fuel tank for rotorcraft. The ALE (Arbitrary Lagrangian–Eulerian) technique was used among the methods of FSI (fluid–structure interaction analysis) and the test conditions specified in the US. Military Specifications (MIL-DTL-27422D) were applied as the conditions for the sloshing movement. As a result of the numerical analysis, the structural soundness of the joints was estimated based on the load imposed on the joints of the external fuel tank. The effects of the sloshing movement on structural soundness were assessed using a margin of safety and the failure index. These were based on the stress to the internal components, metal fittings, and the composite container.

Effect of Evasive Maneuver Against Air to Air Infrared Missile on Survivability of Aircraft

Effect of Evasive Maneuver Against Air to Air Infrared Missile on Survivability of Aircraft

Internal flow and external jet characteristics of double serpentine nozzle with different aspect ratio

In order to increase the survivability of the fighter aircraft, the serpentine nozzle has been applied in series of stealth bombers and unmanned aerial vehicles due to its excellent potentiality of evidently suppressing the infrared radiation signatures and radar cross section emitted by engine exhausts. Among the geometric parameters of the serpentine nozzle, the aspect ratio (AR) at the nozzle exit is one of the most critical parameters for the nozzle design as the infrared suppression effect could be greatly enhanced with the increment of AR by strengthening the mixing between the exhaust plume and atmosphere; the aim of this paper is to study the influence of the AR on the flow characteristics of the double serpentine nozzle. The flow features of six double serpentine convergent nozzles, i.e. AR = 3, 5, 7, 9, 11, 15 respectively, were numerically simulated with the shear stress transport κ–ω turbulent model adopted, which had been validated by the experimental data. The characteristics of internal flow and external jet, and the aerodynamic performances of these six nozzles were compared. Results show that the Ma contours at the symmetric plane are different due to the distinct flow accelerations caused by the change of the curvature and the duct height for diverse AR, and the surface pressure and the shock wave features are different correspondingly. The lateral divergence and the lateral convergence characteristics of the nozzle configuration lead to opposite lateral flow under diverse AR, and the change of lateral width induced different lateral pressure gradient, then lead to various lateral vortex distributions. The length of potential core is the contribution of the comprehensive effects of geometry parameters, and it is decreased with the increase of AR due to the dominated effect of the increased mixing area; however, the declining rate is slowed down. The AR of 5 should be chosen for the best aerodynamic performance of the double serpentine nozzle under the qualifications to completely shield the high-temperature turbine.

Defense Strategy of Aircraft Confronted with IR Guided Missile

Surface-type infrared (IR) decoy can simulate the IR characteristics of the target aircraft, which is one of the most effective equipment to confront IR guided missile. In the air combat, the IR guided missile poses a serious threat to the aircraft when it comes from the front of target aircraft. In this paper, firstly, the model of aircraft and surface-type IR decoy is established. To ensure their authenticity, the aircraft maneuver and radiation models based on real data of flight and exhaust system radiation in the state of different heights and different speeds are established. Secondly, the most effective avoidance maneuver is simulated when the missile comes from the front of the target aircraft. Lastly, combining maneuver with decoys, the best defense strategy is analysed when the missile comes from the front of aircraft. The result of simulation, which is authentic, is propitious to avoid the missile and improve the survivability of aircraft.

An ultra-wideband absorber based on graphene

Stealth technology is of great importance and significance in reducing the radar cross section and improving the survivability of the target aircraft. Absorber is one of the most important structures in stealth technology. However, the present investigations of absorbers mainly focus on the narrow band or multi-band. To extend the operation bandwidth, a graphene-based absorber structure is proposed in this paper. The proposed absorber has a periodic structure whose unit cell consists of a square and a circular graphene-based ring. The surface impedance of the periodic structure can be optimized to match the impedance of the free space in a very wide band by adjusting the electrostatic bias voltage. Then the operation band is significantly extended. By using the commercial software, CST Microwave Studio 2014, the performance of the proposed absorber is studied. The simulated results show that the proposed absorber can absorb electromagnetic (EM) waves in an ultra-wideband from 2.1 to 9.0 GHz, with an absorbing rate of up to 90%. Moreover, the proposed absorber is insensitive to the polarization of the incident wave due to the symmetry of the structure. We also find that the absorber can be tuned to work at any frequency in a range from 2.0 to 9.0 GHz for a fixed geometrical parameter. The equivalent circuit model (ECM) approach and interference theory (INF) are employed to investigate the physical mechanism of the proposed absorber. According to the ECM, we analyze the resonant characteristics of the square and circular graphene rings. Owing to the existence of two different graphene rings, two resonant frequencies are detected. By optimizing the structure parameters of the graphene rings, the two resonant frequencies are brought closer, resulting in the increase of the operation band. On the other hand, the real part of the input impedance of the equivalent circuit reaches up to about 300 Ω and the imaginary part is close to 0 Ω, which provides good matching to the free space, leading to high absorption rate. According to the interference theory, the amplitudes and phases of the direct reflection and the multiple reflections of EM waves are studied. It is found that the destructive interference between the direct reflection and multiple reflection makes the absorber have high performance in an ultra-wideband. The results obtained from ECM and INF are in good agreement with the simulation ones.

Aircraft Combat Survivability Calculation Based on Combination Weighting and Multiattribute Intelligent Grey Target Decision Model

Aircraft combat survivability is defined as the capability of an aircraft to avoid or withstand a man-made hostile environment, which has been increasingly important. In order to give a rational calculation of aircraft combat survivability, an integrated method based on combination weighting and multiattribute intelligent grey target decision model is proposed. Firstly, an evaluation index system containing susceptibility index and vulnerability index as well as their subindexes is established. Then a multiattribute intelligent grey target decision model is introduced. A combination weighting method is brought up based on a modified AHP (analytic hierarchy process) method and the entropy method, offering a rational weight for various indexes. Finally, utilize the multiattribute intelligent grey target decision model to assess the aircraft combat survivability of aircraft, verified by a practical case of five aircraft. The results show that the proposed method is effective and has a great value in engineering application, which will provide useful references for other projects’ evaluation.

Bringing Down Cancer Aircraft: Searching for Essential Hypomutated Proteins in Skin Melanoma

We propose an approach to detection of essential genes/proteins required for cancer cell survival. A gene is considered essential if a mutation with high impact upon the function of encoded protein causes death of the cancer cell. We draw an analogy between essential cancer proteins and well-known Abraham Wald’s work on estimating the plane critical areas using data on survivability of aircraft encountering enemy fire. Wald reasoned that parts with no bullet holes on the airplanes returned to the airbase from a combat flight are the most crucial ones for the airplane functioning: a hit in one of these parts downs an airplane, so it does not return back for the survey. We have envisaged that the airplane surface is a cancer genome and the bullets are somatic mutations with high impact upon protein function. Similarly we propose that genes specifically essential for tumor cell survival should carry less high-impact mutations in cancer cells compared to polymorphisms found in normal cells. We used data on mutations from the Cancer Genome Atlas and polymorphisms found in healthy humans (from 1000 Genomes Project) to predict 91 protein-coding genes essential for melanoma. These genes were selected according to several criteria, including negative selection, expression in melanocytes and decrease in the proportion of high-impact mutations in cancer compared with normal cells. The Gene Ontology analysis revealed enrichment of essential proteins related to membrane and cell periphery. We speculate that this could be a sign of immune system-driven negative selection of cancer neo-antigens. Another finding is the overrepresentation of semaphorin receptors, which can mediate distinctive signaling cascades and are involved in various aspects of tumor development. Cytokine receptors CCR5 and CXCR1 were also identified as cancer essential proteins and this is confirmed by other studies. Overall, our goal was to illustrate the idea of detecting proteins whose sequence integrity and functioning is important for cancer cell survival. Hopefully, this prediction of essential cancer proteins may point to new targets for anti-tumor therapies.

Metal‐Fluorocarbon Pyrolants. XIII: High Performance Infrared Decoy Flare Compositions Based on MgB2 and Mg2Si and Polytetrafluoroethylene/Viton®

AbstractIn the presented work two experimental pyrolants for use in blackbody infrared decoy flares showing higher performance than baseline magnesium/polytetrafluoroethylene/Viton® (MTV) were investigated. These pyrolants are based on fuels hitherto unknown to pyrotechnics: magnesium diboride, MgB2, and dimagnesium silicide, Mg2Si. Both fuels were formulated with polytetrafluoroethylene, PTFE and a fluorocarbon binder Viton® (designated MbTV and MsTV). MsTV yields higher radiance, Lλ (W cm−2 sr−1) in the mid infrared range (2–5 μm) than MTV at same stoichiometry. The volumetric spectral efficiency Eλ (J cm−3 sr−1) of MbTV is also superior to MTV. MbTV thus allows for size reduction of black body countermeasure flares and thereby has potential to enhance the survivability of aircraft in hostile environments. Due to its very high burning rate MsTV qualifies for first fire and igniter applications.

Improving Survivability of Aircraft from Uncontained Gas Turbine Engine Failures

This article describes new measures to improve survivability of aircraft from uncontained gas turbine engine failures. The US military has adopted a common tool—Uncontained Engine Debris Damage Assessment Model (UEDDAM)—for its methodology to consider uncontained events in a more realistic manner. UEDDAM can handle the analysis for the release of the primary rotor-disk segment plus smaller engine debris fragments in directions out of the plane of rotation. The UEDDAM code requires an input of a three-dimensional geometric description of aircraft component positions within the aircraft and thus, in relationship to each other. The description uses a specific input format. Adopting an assessment methodology, like UEDDAM, results in a universal standard and uniformity of debris hazard evaluation across the involved agencies. Maintaining the 3D aircraft geometry model and its components/system functional flow data generated by aircraft manufacturers during their initial hazard assessment would simplify later debris hazard reassessments required by maintenance, repair, or military-modification to a commercial aircraft.

Operation survivability of civil aircraft

The fulfillment of the standard requirements for fatigue and damage tolerance of aircraft structures is the basis for ensuring their safe operation. The paper analyzes the rules formulated in the U.S. FAA Standards and Recommendation Circulars, Soviet Airworthiness Standards, and Russian Aviation Rules. The main requirements for ensuring the damage safety, damage tolerance, and preventing widespread fatigue damages in operating aircraft structures are stated. The results of studying the multiple site damages of full-scale aircraft structures are presented. The principle of the staged increase in the service life limit of Russian aircraft is considered. The rules of Russia are noted to be harmonized with the rules of the United States and Europe. The values of design service lives, scales of fatigue tests of full-scale structures and flight times in operation of different aircraft types are presented. The required values of the statistical and cyclical fracture resistance of structural materials are substantiated, and the achieved values of these characteristics in modern aluminum alloys are presented.

Development of regulatory requirements for fatigue and survivability of civilian transport aircraft

The development of methods and principles of foreign and domestic regulatory requirements that ensure the safe operation of civilian aircraft is considered.