Aircraft Windshield Research Articles

Exponentiated gamma Burr-type X distribution: model, theory, and applications

Several extended Burr-type X distributions have been formed in the past decade. These distributions are widely used in modeling lifetime data as their hazard functions can fit various shapes, such as bathtub, decreasing, and increasing. However, certain extended Burr-type X distributions may not adequately fit the unimodal hazard function. Thus, this paper proposes a new extended distribution with greater flexibility to solve this deficiency: exponentiated gamma Burr-type X distribution. We provide the expressions for the probability density and cumulative distribution functions of the proposed distribution, along with its statistical properties, such as limit behavior, quantile function, moment function, moment-generating function, Renyi entropy, and order statistics. To estimate the model parameters, we employ the maximum likelihood estimation method, and we assess its performance through a simulation study with different sample sizes and parameter values. Finally, to demonstrate the application of this new distribution, we apply it to a real dataset concerning the failure times of aircraft windshields. The results indicate that the new distribution provides a superior fit compared to its submodels and the extended Burr-type X distributions. Moreover, it proves to be highly competitive and can serve as an alternative to certain nonnested models. In summary, the new distribution is highly flexible, capable of modeling a variety of hazard-function shapes, including decreasing, increasing, bathtub, and unimodal patterns.

Numerical simulation of anti-shatter films (ASF) for mechanical post-breakage analysis of retrofitted glass

Post-breakage strength and residual mechanical capacity improvements are important tasks for load-bearing structural components in general, and even more for glass elements, in order to protect people from injury in case of breakage. For this reason, among others, the design of glass components and structures is based on key concepts that are generally summarized in structural safety, robustness and redundancy. With regard to the last fundamental requirement, nowadays the use of laminated glass (LG) sections is spread for many applications and new projects, such as automotive or aircraft windshields, but especially curtain walls and many other load-bearing applications in buildings. This strategy derives from the intrinsic safety and security levels of LG sections after possible glass breakage. When LGs are not available (i.e., existing components), anti-shatter safety films (ASF) for the retrofit of monolithic glass elements are expected to provide very similar post-breakage structural performances against bending and impact actions, by reducing the possible spread of glass shards. Besides, the residual load-bearing capacity of glass components retrofitted by ASF is still challenging to quantify. In this paper, the Cohesive Zone Model (CZM) theory is considered to investigate, with the support of experiments and Finite Element (FE) numerical models, the performance of small-scale monolithic glass specimens retrofitted by ASF under bending loads. Different ageing procedures and imposed displacement-rates are considered to evaluate the influence of basic operational parameters, such as temperature and humidity, on the mechanical efficiency of common ASF layers. In doing so, the sensitivity of fundamental input parameters (i.e., maximum tensile strength of glass and fracture energy of the ASF adhesive) on the mechanical performance at pre- and post-breakage stages of retrofitted monolithic glass elements is explored.

New design of materials, order and thicknesses of an aircraft windshield behaviour layers to increase its resistance against repeated bird impacts

Abstract There are instances when an aircraft encounters a bird’s flock or faces a heavy hailstorm, causing the windshield to sustain consecutive impacts. Therefore, the investigation of windshield resistance against repeated impacts is crucial. In this research, various tests such as tensile, split Hopkinson pressure bar (SHPB), and three-point bending are conducted to extract the mechanical properties of the materials used in a five-layers windshield under high strain rates. Using this information, the bird impact on the windshield is simulated using the smooth particle hydrodynamics (SPH) method, and the results are compared with real bird impact test outcomes, and the validation of this simulation is confirmed. The simulation of two consecutive bird strikes indicates the current windshield lacks sufficient resistance against successive dual impacts; in such scenarios, the second bird penetrates the windshield after breaking it and tearing the interlayer. Considering new materials and thicknesses for each windshield layer, a Taguchi experimental design method is employed to examine various layer arrangements with different materials and thicknesses. The configurations in which the windshield can withstand a maximum of three bird impacts in succession are identified. Subsequently, using the “the smaller, the better” criterion in the Taguchi optimisation approach, the configuration that not only prevents bird penetration but also minimises the maximum strain in the inner layer is selected as the desired outcome. Thus, a new five-layer windshield with new materials and thicknesses is presented, which is resistant to the repeated collision of up to three birds, tearing in the interlayer and bird penetration does not happen.

Zwitterionic cellulose nanofibers-based hydrogels with high toughness, ionic conductivity, and healable capability in cryogenic environments

Extreme environmental conditions often lead to irreversible structural failure and functional degradation in hydrogels, limiting their service life and applicability. Achieving high toughness, self-healing, and ionic conductivity in cryogenic environments is vital to broaden their applications. Herein, we present a novel approach to simultaneously enhance the toughness, self-healing, and ionic conductivity of hydrogels, via inducing non-freezable water within the zwitterionic cellulose-based hydrogel skeleton. This approach enables resulting hydrogel to achieve an exceptional toughness of 10.8 MJ m−3, rapid self-healing capability (98.9 % in 30 min), and high ionic conductivity (2.9 S m−1), even when subjected to −40 °C, superior to the state-of-the-art hydrogels. Mechanism analyses reveal that a significant amount of non-freezable water with robust electrostatic interactions is formed within zwitterionic cellulose nanofibers-modified polyurethane molecular networks, imparting superior freezing tolerance and versatility to the hydrogel. Importantly, this strategy harnesses the non-freezable water molecular state of the zwitterionic cellulose nanofibers network, eliminating the need for additional antifreeze and organic solvents. Furthermore, the dynamic Zn coordination within these supramolecular molecule chains enhances interfacial interactions, thereby promoting rapid subzero self-healing and exceptional mechanical strength. Demonstrating its potential, this hydrogel can be used in smart laminated materials, such as aircraft windshields.

Experimental research on blowing-rain intensity and uniformity of rain tunnel for aircraft rain removal testing

The objective of the present study is to characterize a rain tunnel that is used for performance testing of aircraft windshield rain removal systems. The rain tunnel in the present study is an open jet wind tunnel with six full cone pressure swirl nozzles arranged at its outlet. Experiments are conducted with water at room temperature as the working medium. The influence of total water supply flow rate and air velocity on the blowing-rain intensity and uniformity is studied. The total water supply flow rate varies from 0.57 m3/h to 1.03 m3/h, while the pressure at the inlet of the nozzle ranges from 1.44 bar to 6.52 bar. The air velocity of 30 m/s, 40 m/s, and 50 m/s is studied. A special test setup has been designed for measurements of the blowing-rain intensity and uniformity. Experimental results indicate that the blowing-rain intensity and uniformity both increase with the increasing total water supply flow rate and decrease with the increasing air velocity.

Graphene-based optically transparent metasurface for microwave and terahertz cross-band stealth utilizing multiple stealth strategies

Stealth, as a miraculous physical phenomenon, has received widespread attention from the scientific and engineering communities for a long time. Optically transparent stealth devices are of significant importance for the stealth capabilities of aircraft windshields and solar panels. However, the current stealth implementations are limited to a single frequency band due to the strong dispersion of passive materials so that cross-band stealth still remains challenging. In this paper, a novel cross-wavelength stealth strategy is proposed based on multi-layer graphene transparent metasurface, which achieves stealth both in microwave and terahertz frequency bands. Strong resonance is designed to achieve high absorption in the microwave band and diffuse scattering is employed for RCS reduction in the terahertz band. Materials such as graphene and ITO are employed to achieve optical transparency and flexibility of the metasurface. The above design is implemented using numerical simulations and experiments, and the results are in good agreements. This design method that integrates multiple stealth strategies opens up a new approach for cross-band stealth, with potential applications in countering advanced electromagnetic detection.

Airworthiness Compliance Verification of Bird Strike on Civil Aircraft Windshield Frame

With the frequent occurrence of bird strikes, minimizing the impact damage effect of birdstrike on flight always is the goal of airworthiness certification. As a large windward component in front of the aircraft, the windshield, and frame have more probability to be suffered from birdstrike. This paper introduces the common connection forms of the windshield frame structure of civil aircraft, and through the interpretation of the airworthiness requirements related to windshield in CCAR-25, puts forward the process and method of compliance verification of windshield frame birdstrike. Based on the SPH method, the dynamic analysis of bird impact on windshield window frame is carried out, the test is carried out to verify that the analysis method is reasonable and conservative, and the results show that the bird impact performance of the windshield frame structure meets the airworthiness requirements.

Redesign an aircraft windshield to improve its mechanical resistance against simultaneous bird impacts

The bird impact on aircraft components is one of the most serious accidents which can happen in the aviation industry. Among the various parts of an aircraft, the bird impact on the windshield is more important due to the possibility of causing injury to the pilot. Standard windshields are designed to withstand a bird strike, however, in a group flight of birds, several birds can strike the windshield at the same time. The results of practical tests and simulations show that the current windshields are seriously damaged in the simultaneous collision of several birds and the possibility of birds penetrating the cabin is very high. In this research the mechanical properties of standard windshield constituent materials are obtained. Initially practical tests are carried out and simulation results are verified for single bird strike. Using these results, the simultaneous impact of three birds on a windshield is simulated. It was shown that the resistance of the standard windshield against simultaneous collisions is insufficient. So the thicknesses of the windshield layers are determined in such a way that the new windshield is resistant and bird penetration into the cabin does not happen.

Effect on damage of aircraft windshield impacted by light UAV with different postures

Abstract To study the performance of the main windshield of a commercial aircraft that has been verified to be airworthy by bird-strike tests against unmanned aerial vehicle (UAV) impact at high-speed, a typical light UAV with various possible flight postures and the main windshield of a commercial aircraft are considered. The transient impact responses at critical moments, energy change and contact force of a multi-layer windshield impacted by a UAV with different postures are investigated using a simulation method based on the models verified by the high-speed impact test between the whole UAV and the full-size nose. This study shows that the flight posture of the UAV has a significant effect on the damage to the windshield. When the abdomen of a typical light UAV maintains a posture parallel to the plane of the windshield, the high-speed impact would cause catastrophic damage to the windshield and no longer be airworthy. Simultaneously, the damage to the aircraft windshield caused by UAV collision is far more serious than that caused by bird strikes under similar collision conditions. The mass-concentrated components of the UAV and their high-hardness characteristics are the main factors of affecting multi-layer glass of windshield damage. The degree of damage to the windshield is positively related to the absorbed energy rather than the impact contact force. In this study, the impact simulation results between the windshield and UAV with different flight postures are verified qualitatively by testing, which provides a rational understanding and technical pre-research support for emerging and increasingly frequent potential safety hazards in air transport practice.

Response Optimization of Machining Parameters using MCDA-Vikor Method for Acrylic Glass with AHAJM

Abstract: Abrasive Hot Air Jet Machining (AHJM) is becoming one of the most prominent machining techniques forPolymethyl Methacrylate (PMMA) and other brittle materials. In this attempt has been made to combine abrasive and hot air to form an abrasive hot air jet. Abrasive hot air jet machining can be connected to different tasks, for example, boring, surface scratching, scoring and small scale completing on the glass and its composites. The impact of air temperature onthe material expulsion rate connected to the procedure of glass carving and scoring is talked about in this article. The unpleasantness of the machined surface is additionally investigated. It is discovered that the material removal rate (MRR) increments as the temperature of transporter media (air) is expanded. In the present work to be attempt to investigate machining characteristics of PMMA material on hot air abrasive jet machining. In hot air abrasive jet machining(HAJM) abrasive particles stay on abrasive particle stay molten by compacted air in a closed chamber and are intensive over the objective surface over a nozzle the stream of particles coming out of the nozzle through very high velocity’s (175-300m/s) impacts the objective surface and eliminates the material by destruction. The investigation has to be carried on to study the effect of process parameters as material removal rate(MRR) as surface roughness(SR) with different input parameters like Air Pressure, , Size Of Abrasives , Stand-Off Distance ,Temperature Of Carrier Gas. In this experimental process Tungstencarbide coated nozzles were to be used flow of silicon carbide(sic) particles will be used.The Poly(methyl methacrylate) (PMMA), furthermore saw as acrylic glass, acrylic material, or plexiglass as suitably as by using the change names Plexiglas, Crylux, Lucite, Acrylate. PMMA it is an unquestionable thermoplastic .the creation formula of PMMA is (C5O2H8)n it has incredible properties to, for instance, lightweight, 92% Transparent observable light effect inside 3mm of thick material, extraordinary solidarity to consider another polystyrene. it's for the most part important in these zones, for instance, Because of its direct properties, lightweight and preferable quality took a gander at over glass, It was broadly usedto make aircraft windshields, shades and weapon turrets. After this couple of different business applications were made for PMMA, for instance, glass material, façade arrangement, publicizing, vehicle headlamps, etc.,

Investigation of Li2O/Na2O effect on the atomic structure and mechanical properties of aluminosilicate glasses using molecular dynamics simulation, Raman and NMR spectroscopy

Aluminosilicate glasses are extensively used in flat panel displays and aircraft windshields because of their superior mechanical characteristics. Understanding the influence of the components on the glass network structure and mechanical properties is essential to designing aluminosilicate glasses with desirable mechanical functions. In this paper, the molecular dynamic simulations were used to obtain atomic structural information of the glasses, and the results were compared with Raman, Nuclear magnetic resonance, X-ray photoelectron spectroscopy, Differential thermal analysis, and Vickers hardness to elucidate the effect of Li2O/Na2O on the atomic structure and mechanical properties of aluminosilicate glasses. We show through experiments and molecular dynamic simulations that an increase in the Li2O/Na2O ratio can increase the mechanical properties of the glass. Li ions reorganized the glass network by partial conversion of [AlO5] to [AlO4] units and changes in the bridging oxygen/non-bridging oxygen ratio, which in turn alters the glass on a longer scale, for example, by sharpening the ring distribution and an increase in the number of loops, leading to structural clustering of the glass network and increased mechanical properties. This composition-structure-property relationship can be used to design aluminosilicate glasses with particular properties.

Flexible Extension of the Lomax Distribution for Asymmetric Data under Different Failure Rate Profiles: Characteristics with Applications for Failure Modeling and Service Times for Aircraft Windshields

A novel four-parameter lifetime Lomax model is presented and investigated within the scope of this paper. The failure rate of the innovative model can be “monotonically decreasing failure rate,” “monotonically increasing failure rate,” or “constant failure rate,” and the density of the model can be “asymmetric right skewed,” “symmetric,” “asymmetric left skewed,” or “uniform density”. The new density is expressed as a blend of the Lomax densities that have been multiplied by an exponent. New bivariate Lomax types were created for our research. The maximum likelihood technique was utilized. We performed simulated experiments for the purpose of evaluating the finite sample behavior of maximum likelihood estimators, using “biases” and “mean squared errors” as our primary metrics of analysis. The novel distribution was evaluated based on a number of pertinent Lomax models, including Lomax extensions that were generated on the basis of odd log-logistic, Kumaraswamy, beta, gamma, and Topp–Leone families, among others. The newly developed extension demonstrated its relevance by predicting the service and failure times of datasets pertaining to aircraft windshields.

Survival Analysis of the PRC Model from Adaptive Progressively Hybrid Type-II Censoring and Its Engineering Applications

A new two-parameter statistical model, obtained by compounding the generalized-exponential and exponential distributions, called the PRC lifetime model, is explored in this paper. This model can be easily linked to other well-known six-lifetime models; namely the exponential, log-logistic, Burr, Pareto and generalized Pareto models. Adaptive progressively hybrid Type-II censored strategy, used to increase the efficiency of statistical inferential results and save the total duration of a test, has become widely used in various sectors such as medicine, biology, engineering, etc. Via maximum likelihood and Bayes inferential methodologies, given the presence of such censored data, the challenge of estimating the unknown parameters and some reliability time features, such as reliability and failure rate functions, of the PRC model is examined. The Markov-Chain Monte Carlo sampler, when the model parameters are assumed to have independent gamma density priors, is utilized to produce the Bayes’ infer under the symmetric (squared-error) loss of all unknown subjects. Asymptotic confidence intervals as well as the highest posterior density intervals of the unknown parameters and the unknown reliability indices are also created. An extensive Monte Carlo simulation is implemented to investigate the accuracy of the acquired point and interval estimators. Four various optimality criteria, to select the best progressive censored design, are used. To demonstrate the applicability and feasibility of the proposed model in a real-world scenario, two data sets from the engineering sector; one based on industrial devices and the other on aircraft windshield, are analyzed. Numerical evaluations showed that the PRC model furnishes a superior fit compared to seven other models in the literature, including: alpha-power exponential, log-logistic, Nadarajah–Haghighi, generalized-exponential, Weibull, gamma and exponential lifetime distributions. The findings demonstrate that, in order to obtain the necessary estimators, the Bayes’ paradigm via Metropolis–Hastings sampler is recommended compared to its competitive likelihood approach.

Study on the Aging Mechanism of Aerospace Plexiglass by Ultraviolet

As the main material of aircraft windshield glass, the safety and reliability of aviation plexiglass are very important. YB-3 aviation Plexiglass was used as aircraft windshield material for a four-seater electric aircraft developed in China to explore the mechanism of ultraviolet aging. The artificially accelerated aging test of YB-3 aviation plexiglass was carried out, and the mechanical and thermodynamic system of YB-3 aviation Plexiglass after aging was studied. Through the thermogravimetric dynamic analysis, it is to explore the internal aging mechanism of PMMA photolysis materials, and combined with the mechanical test data to quantitatively and qualitatively reveal the aging law of YB-3 aviation plexiglass under ultraviolet radiation. The results show that the tensile ultimate stress decreases from 72.74 MPa to 45.63 MPa when the aging time reaches 1440 h. During the aging process, the elastic modulus decreased from 4.45 GPa to 3.68 GPa and then increased to 4.12 GPa. The results show that the photolysis of YB-3 aero-plexiglass under ultraviolet radiation first results in the fracture of the polymer and then the production of small molecules, which leads to the decrease of tensile resistance and the improvement of thermal stability of the material.

Study on bird impact response of windshield glass of all general aviation aircraft

With the improvement of aircraft flight speed, bird impact is easy to cause serious accidents such as windshield breakdown, aircraft destruction and human death. In order to improve the bird impact resistance of aircraft windshield glass, the dynamic response of windshield glass (YB-3 plexiglass) after bird impact of small general-purpose aircraft flying at cruise speed was studied. By establishing the bird impact windshield glass model and adopting the fixed restraint mode around, the windshield glass is impacted at the speeds of 200km/h, 220km/h and 250km/h and the angles of 30°, 60° and 90°, respectively. The changes of stress-strain, displacement and energy absorption of the windshield glass under the impact of bird body, as well as the effects of different impact speeds and impact angles on the dynamic response of the glass are analyzed. It is found that during the whole impact process, the stress and strain of YB-3 plexiglass will reach the peak in a short time, then oscillate back and forth in a period of time, and the final residual deformation is small. With the increase of impact velocity, the stress, strain and displacement of glass will increase accordingly; With the increase of the impact angle, the energy absorbed by the windshield glass decreases accordingly, and the damage and deformation around the impact point are reduced. By studying the bird impact of the windshield of small general-purpose aircraft, it provides a theoretical basis for the airworthiness certification of general-purpose aircraft and the design optimization of windshield glass.

Numerical simulation of rain accumulation on aircraft windshield

Aircraft windshield rainfall process is a complex two-phase flow problem that includes the movement, collision, fragmentation, merging of raindrops, water film adsorption and water film flow. In this paper, a numerical method based on FLUENT is proposed to simulate this process. And the experiment of rain accumulation on flate-plate is carried out to verify the numerical method. This method combines the Discrete Phase Model and the Lagrangian Water Film Model. The control variable method is adopted to study the effects of aircraft flight speed, Angle of Attack(AOA), rainfall intensity and raindrop temperature on windshield rainfall. The results show that the impact of aircraft AOA on the windshield rainfall is relatively low, while the aircraft flight speed and rainfall intensity are positively correlated with the degree of windshield rainfall. The raindrop temperature has no significant effect on the windshield rainfall, but the lower temperature will bring more difficulty to remove raindrops.

Molecular dynamic simulations study on the structure and properties of Li2O-containing magnesium aluminosilicate glasses

Magnesia aluminosilicate glass has important applications value in the fields of composite fiber reinforcement, flat panel display, aircraft windshields and so on because of its excellent chemical stability and good mechanical properties. In this paper, the molecular dynamic simulations were used to obtain structural information of the glasses, and the results were compared with Raman, X-ray photoelectron spectroscopy, Differential thermal analysis, and Vickers hardness to elucidate the effect of Li2O introduction on the structure and properties of MgO-Al2O3-SiO2 glasses. The transformation mechanism of oxygen type and polyhedral with the process of Li2O content was investigated, and focusing on the effect of network connectivity of the glass on the transformation temperature and hardness. The results indicated that at low Li2O content (< 3 mol%), Li ions play the role of charge compensator and reinforce the network structure of MgO-Al2O3-SiO2 glasses. When the Li2O content exceeds 3 mol%, the excess Li2O breaks the backbone of the Al-Si network structures that to the reduction of the glass network connectivity. The glass transition temperature and hardness of Li2O-MgO-Al2O3-SiO2 glasses reach a maximum at a Li2O addition of 3 mol%, while the corresponding simulated structures (AlO5 and Network Connectivity) show the most stable network structure.

Формирование и отображение видеоинформации в бортовых мультиспектральных системах улучшенного видения

The article considers the results of long-term research and real flight tests for developing a multichannel system for enhanced vision in difficult for aircraft crew visibility conditions. The multicomponent nature of the aggregate video signal generated by a multispectral video system is shown, justifying its representation in color and the need to develop a color indicator of the aircraft windshield to obtain a better quality of situational awareness for pilot compared to the capabilities of traditionally used monochrome indicators. A method for integrating monochrome images of multichannel enhanced vision system spectral channels into a color multicomponent image is proposed. For more natural perception of the resulting color images by the human eye, the spectrum of the spectral characteristics of the video channels is rearranged in the direction of decreasing wavelength. For the most common RGB color image format, the red component R of the display system records the image of the long-wave thermal range, the green component G records the image of the mid-wave infrared range, the blue component B records the image of the short-wave visible television range. The resulting pseudo-color image allows unambiguous restoring the original images. This proves the absence of information loss during image integration. Since there are no colored windscreen displays yet, a method for reproducing a pseudo-color image on a mono-chrome display is proposed. To convert a pseudo-color image to monochrome one, methods are used in which color contrasts are preserved in the form of tonal contrasts. The advantages of the proposed technology are demonstrated on real examples

Experimental and Numerical Investigations of Bird Models for Bird Strike Analysis

The article presents experimental and numerical studies of bird models during impacts with rigid and deformable targets. The main aim of the studies is the validation of bird models in order to prepare them for the numerical simulation of bird impact against aircraft windshields and other parts of aircraft, thus improving the air transportation safety by providing cost-effective solutions for designing bird strike-resistant aircraft. The experimental investigations were conducted with a special set-up of a gas gun equipped with high-speed cameras, tensiometers and force sensors. The simulations were developed on the basis of LS-DYNA software by means of the SPH method for the bird model shape of the cylinder with hemispherical endings at the speed of 116 m/s. The results of studies into such things as the impact force, pressure and bird model deformation were compared. Moreover, the authors’ and other researchers’ results were assessed. It can be noted that the curves of the impact force obtained as a result of the numerical analysis correlated well with the experimental ones.

Structural and dynamic properties of MgO–Al2O3–SiO2 glasses from molecular dynamics simulations and NMR

Magnesium aluminosilicate glasses have a wide range of applications in composite fiber reinforcements, aircraft windshields, due to their excellent chemical stability and mechanical properties. In this work, molecular dynamics simulations were used to obtain the short- and medium-range structural evolution of MgO/Al2O3 in MgO–Al2O3–SiO2 glass. The structural information was verified using a combination of combining Raman and Nuclear Magnetic Resonance (NMR) spectroscopy. The composition-structure-property relationship of the MgO–Al2O3–SiO2 glasses was constructed, using high-temperature viscosity results calculated by the Einstein-Stoke equation. The results showed that with the increase of MgO/Al2O3 ratio, Mg2+ changed from charge compensator to network modifier, which led to the gradual depolymerization of the glass network. Moreover, with the gradual replacement of Si by Al in the glass network, the disorder of the glass system increases, evidenced by the high-frequency Raman bands and the average chemical shifts of [AlOn] (n = 4, 5) shift linearly. In addition, we found that the de-polymerization led to a decrease in viscosity and an increase in fragility. The viscosity is negatively correlated with both the fragility and the atomic diffusion coefficient. It provides a theoretical basis for improving the preparation process of MgO–Al2O3–SiO2 glass and optimizing the glass properties.