Runway Debris Research Articles

Experimental and numerical investigation on Multiwalled carbon nanotubes (MWCNTs) dispersed CFRP laminate subjected to spherical and conical impacts

ABSTRACT As lightweight and load-bearing efficiency needs have grown, conventional metal has steadily given way to carbon fibre-reinforced polymer (CFRP) laminates. Also, CFRP laminates are more prone to localised damage due to impact loads like tool drop, runway debris and hail stone. This paper, investigated the penetration and perforation behaviour of CFRP laminate reinforced with 0.2 and 0.5 wt% MWCNTs. The projectile impact experiment was conducted using spherical and conical projectiles and the impact resistance was evaluated. The results revealed that 0.5 wt% MWCNTs embedded in CFRP laminate provided better impact resistance to both projectiles. The ballistic limit velocity was enhanced by 14.2% and 17.9% for spherical and conical projectiles, respectively, in the case of 0.5 wt% MWCNTs. Furthermore, numerical simulations were performed using an orthotropic model with Chang-Chang composite failure criteria. The results from numerical findings were consistent. It was concluded that MWCNTs reinforcement improves the projectile impact resistance and energy absorption.

Impact damage assessment of sandwich structures with CFRP face sheets reinforced by CNTs in thermal environment

The damage behaviour of honeycomb sandwich structures with carbon nanotube (CNT) reinforced composite face sheets under high velocity impact at elevated temperatures is investigated in the present study. In order to endure the out-of-plane loading events such as bird hit, runway debris and hail stone impact, CNTs are introduced into the matrix system with the intention of improving the damage resistance. CNT reinforced carbon-epoxy composites with various weight percentages such as 0.2, 0.4, 0.6 and 0.8 were manufactured as quasi-isotropic laminates. Sandwich structures were prepared and tested under high velocity impact at room temperature and elevated temperature (393 K) using a single stage gas gun. Macro structural observations were performed on the perforated specimens and the damage area, depth, central deflection and bulging height were measured. At room temperature, the impact damage pattern was characterized by matrix cracking, fiber breakage, fiber debris, fiber push away, fiber peel up and push delamination. Plastic deformations of the matrix and kink band formation are the significant damage modes in the thermal environment. Adding a higher proportion of nanoscale reinforcement is not always judicious to get improved impact resistance; rather, the temperature dependency must be considered when designing the CFRP composite for structural applications.

Analysis of Low-Velocity Impact Properties of Kevlar 149-Carbon Fiber Reinforced Polymer Matrix Composites

Aircraft undergoes various low-velocity impacts such as bird strike, runway debris, foreign tools drop, etc. on its structure. Kevlar is widely used in several components and structure of the aircraft as Kevlar is an organic fiber from an aromatic polyamide family. Carbon fiber has advantages like high stiffness and properties like that of kevlar. The present study focuses on the analysis of low-velocity impact properties of kevlar 149-carbon fiber reinforced polymer matrix composite material. In this analysis, kevlar 149-carbon fiber, pure kevlar 149 by 10 layers of laminate and pure carbon fiber by 10 layers of laminate are impacted by ball material with a mass of 8g at velocity of 9m/s. The ball impact on the laminate is simulated using LS-DYNA. The max. principal stress, absorbed energy, velocity and displacement of K149C, CK149, KK149CC, CCKK149, KK149 and CC are obtained and compared with all the six composite laminates. The composite laminate, K149C, proves to be the best laminate for aircrafts as it possesses a higher max. principal stress and lower displacement.

A Critical Review of Physical Models in High Temperature Multiphase Fluid Dynamics: Turbulent Transport and Particle-Wall Interactions

Abstract This review article examines the last decade of studies investigating solid, molten, and liquid particle interactions with one another and with walls in heterogeneous multiphase flows. Such flows are experienced in state-of-the-art and future-concept gas turbine engines, where particles from the environment, including volcanic ash, runway debris, dust clouds, and sand, are transported by a fluid carrier phase and undergo high-speed collisions with high-temperature engine components. Sand or volcanic ash ingestion in gas turbine engines is known to lead to power-loss and/or complete engine failure. The particle-wall interactions that occur in high-temperature sections of an engine involve physics and intrinsic conditions that are sufficiently complex that they result in highly disparate and transient outcomes. These particles, which often times are made up of glassy constituents called calcium–magnesium–alumino–silicate (CMAS), are susceptible to phase change at combustor temperatures (1650°), and can deposit on surfaces, undergo elastic and plastic deformation, rebound, and undergo breakup. Considerable research has been put into developing empirical and physics-based models and numerical strategies to address phase interactions. This article provides a detailed account of the conceptual foundation of physics-based models employed to understand the behavior of particle-wall interaction, the evolution of numerical methods utilized for modeling these interactions, and challenges associated with improving models of particle-particle and particle-wall interactions needed to better characterize multiphase flows. It also includes description of a testbed for acquiring canonical data for model validation studies.

Experimental Damage Evaluation of Honeycomb Sandwich with Composite Face Sheets under Impact Load

Aerospace structures are highly vulnerable to impact loads whose damage tolerance, and its resistance vary over the range of impact velocity. Honeycomb sandwich structures are used in aerospace industries where mass efficient and impact resistant structures are needed. However, the structural integrity of these structures is reduced by impact load due to tool drop, runway debris, hailstones and improper handling of the structure. A thorough investigation of the damage behaviour of honeycomb sandwich under low-velocity impact and the post-impact residual strength determination is required to design a crashworthy lightweight structure. This paper presents the experimental evaluation of specific energy absorption using Charpy impact, residual compressive strength by compression after impact and damage evaluation of honeycomb sandwich structures having composite face sheets. Parametric studies on composites and honeycombs are carried out by varying the cell size, cell thickness, core height, impact velocity, thickness and orientation of lamina. Densely packed thick honeycombs provide higher fracture energy. Under transverse compressive loading, the honeycomb core undergoes cell wall buckling, crushing and densification. Load-displacement history under in-plane compression and compression after impact for different impact energies is observed. The present study contributes for the understanding how various parameters affect the characteristics of face sheet indentation and plastic buckling of honeycomb sandwich structures with composite face sheets, thereby providing useful guidelines for its potential applications in impact engineering.

Modelling the effect of projectile hardness on the impact response of a woven carbon-fibre reinforced thermoplastic-matrix composite

In the present paper numerical modelling results are described to predict the effects of the hardness of a projectile impacting a woven carbon-fibre reinforced thermoplastic-matrix composite. The projectiles are prepared from either relatively soft gelatine or hard high-density polyethylene (HDPE) materials, of the same mass, and are fired from a gas-gun at about 60 m s−1 to impact a woven carbon-fibre reinforced poly(ether-ether ketone) (woven CF/PEEK) composite. A two-dimensional, elastic, finite-element analysis (FEA) model is developed to simulate the gas-gun impact experiments and study the impact damage processes, and this numerical model is relatively computationally efficient. This FEA model makes predictions for the plastic flow for the gelatine projectile and the elastic deformation of the polyethylene projectile. In addition, the model predicts the effects of the hardness of the projectile on (a) the deformation of the impacted composite specimens and (b) the location and extent of damage in the composites. Very good agreement between the predictions from the model and the experimental measurements is observed. This research is of key importance in studying the behaviour of thermoplastic-matrix composites under impact loading by various types of threat such as relatively soft bodies, e.g. birds and hard objects, e.g. dropped-tools and runway debris.

The Impact Performance of Woven-Fabric Thermoplastic and Thermoset Composites Subjected to High-Velocity Soft- and Hard-Impact Loading

The present paper investigates the impact performance of woven-fabric carbon-fibre composites based upon both thermoplastic- and thermoset-matrix polymers under high-velocity impact loading by conducting gas-gun experiments at impact velocities of up to 100 m.s−1. The carbon-fibre reinforced-polymers (CFRPs) are impacted using soft- (i.e. gelatine) and hard- (i.e. aluminium-alloy) projectiles to simulate either a soft bird-strike or a hard foreign-body impact (e.g. runway debris), respectively, on typical composites employed in civil aircraft. The out-of-plane displacements of the impacted composite specimen are obtained by means of a three-dimensional Digital Image Correlation (DIC) system for the soft-projectile impact on the composites and the extent of damage is assessed both visually and by using portable C-scan equipment. The perforation resistance and energy absorbing capability of the composites are also studied by performing high-velocity impact experiments using the hard-projectile and the resulting extent and type of damage are identified. In addition, a Finite Element (FE) model is also developed to investigate the interaction between the projectile and the composite target.

Experimental determination of the aerodynamic coefficients of spinning bodies

ABSTRACTTo accurately predict the probabilities of impact damage to aircraft from runway debris, it is important to understand and quantify the aerodynamic forces that contribute to runway debris lofting. These lift and drag forces were therefore measured in experiments with various bodies spun over a range of angular velocities and Reynolds numbers. For a smooth sphere, the Magnus effect was observed for ratios of spin speed to flow speed between 0.3 and 0.4, but a negative Magnus force was observed at high Reynolds numbers as a transitional boundary layer region was approached. Similar relationships between lift and spin rate were found for both cube- and cylinder-shaped test objects, particularly with a ratio of spin speed to flow speed above 0.3, which suggested comparable separation patterns between rapidly spinning cubes and cylinders. A tumbling smooth ellipsoid had aerodynamic characteristics similar to that of a smooth sphere at a high spin rate. Surface roughness in the form of attached sandpaper increased the average lift on the cylinder by 24%, and approximately doubled the lift acting on the ellipsoid in both rolling and tumbling configurations.

The analysis of the worst-case distribution of the damage in composite material imposed by a low velocity impact

Low velocity impact causes barely visible impact damage (BVID) in composite material, which can be missed at technical inspection. Usual cases during composite product lifetime are the tool drop, hailstones, runway debris etc. The proposed approach avoids the direct modelling of impact process and realizes the minimum possible residual strength for specific damage based on the worst distribution of matrix, fiber and interface micro damages and its accumulation after impact. The minimum possible residual strength condition is fulfilled by the decreasing the stiffness of the laminate via energy absorption form the impactor and composite material collision. It is assumed, that the portion of the kinetic energy of an impactor is transformed into microcracks of fractured matrix materials by several damage modes but the other portion is transformed back to the impactor. The presented method gives as a result the distribution of damage parameters, which reduces stiffness of the material using gradient descent method and provides the worst distribution of damage densities, which associated with the stiffness and gives the direct analogue to the structural topology optimization algorithm. The simple explanation of presented method can be formulated as a search of the worst case of damage distribution in the material for residual strength of the structure with restriction on total energy spent on material damaging.

Experimental investigation of small fatigue crack growth due to foreign object damage in titanium alloy TC4

The ingestion of runway debris during takeoff, landing and low-flying of aircraft has been a major concern for gas turbine engines. The small craters or notches introduced by particles impacting blades are commonly known as foreign object damage (FOD). The objective of this paper is to identify the initiation and propagation behavior of small fatigue crack originating from FOD crater in titanium alloy TC4. FOD was simulated by firing steel sphere projectile onto the surface of flat specimen at 30°, 60° and 90°. Replication technique based on a two-part silicon mixture was used to observe the initiation and growth process of FOD-initiated crack. The results reveal that all the cracks nucleate from the micronotches at the material pileup of FOD crater rim. The growth process of FOD-initiated crack consists of two stages. In the first stage, the crack propagates merely inside the crater. Once exceeding ~500 µm in length, the crack will grow into the second stage, in which the crack extends rapidly both inside and outside the FOD crater. Moreover, the growth rates of FOD-initiated cracks are lower than naturally-initiated cracks. Of all the three tested impact angles, the 60° impact seemed to lead to the most crucial decline in fatigue resistance. A linear relationship exhibits between the fatigue lifetime and crater cross-section area of FODed specimens.

Multiscale Damage Modeling on Aeronautical Composite Under Low Energy Impact

The purpose in this paper is to investigate about the behavior of aeronautics composite material subjected to a low energy impact. Low velocity impact in aircraft composite panels is a matter of concern in modern aircraft and can be used either from maintenance accidents tools or in-flight impact with debris. The proposed study considers the dynamics of impact between a small piece of granular material and a large body of composite material. The principal aim is to simulate the impact of runway debris throw-up by the landing gear against an airplane structure. In this simulation, I want to investigate on CFRP composite panels affected by granular particles at low speed in theoretical and experimental tests. The finite element analysis, initially on the macroscale and subsequently on the microscale, shows the damage inside the composite according to the experimental results, but by itself, this classic numerical approach is little suitable to investigate the complete phenomenon. Developing the question, in first step by the classical approach, appears difficult on macro and microscale relationship besides their reciprocal influence over the deformation field. To resolve the last question, I will perform the first step on macroscale FEM analysis and then reduce from the size and effects over an opportune created RVE, such that microscale main effects as local delamination can be reproduced.

Runway Debris Impact on Aircraft Composite Parts

In this paper, we perform the behavior of aeronautics composite material subjected to a low energy impact. The proposed study considers the dynamic impact between a small piece of granular material and a large body of composite material. The principal aim is to simulate the impact of runway debris thrown up by the landing gear against an airplane structure. In the simulation, a CFRP composite panel impacted by granular particles at low speed is considered. The finite element analysis, initially on the macroscale and subsequently on the micro-scale, shows the delamination inside the composite according to the experimental results.

Impact Localization on Composite Wing Using a Single FBG Sensor and Error Outlier Based Impact Localization Algorithm

Low velocity impact on composite structure can result in occurrence of barely visible impact damage (BVID) which are difficult to detect. Aircraft structures are vulnerable to such BVID because of low velocity impact due to runway debris, bird strike, tool drop, etc. Therefore, low velocity impact monitoring of composite structure is highly desirable for impact detection and localization. Additionally, SHM of large-scale structures with fewer numbers of sensors is desirable to reduce the complexity involved with the dataacquisition and processing. In this paper, feasibility of localizing low velocity impact on composite structure using a single sensor was investigated. Three FBG sensors were attached on the surface of the full-scale composite wing and the signal from each of the FBG sensor was processed using the error outlier based impact localization algorithm to predict the location of the impact. The localization results demonstrated the feasibility of localizing impact on composite structure using a single FBG sensor; overall, the impacts were localized with average error of about 26.6 mm.

Effect of high strain rate on glass/carbon/hybrid fiber reinforced epoxy laminated composites

Abstract Composites are efficient to deal with tensile loads than metals. Now-a-days, metals are replaced with composites owing to their higher strength to weight ratio and are extensively used in aircraft wing and fuselage structures. These structures are subjected to high strain rates during impact loadings, such as bird hit or run-way debris impact. In order to design robust composite structures, it is important to understand the strain-rate-dependent behavior of composite materials. In this study, influence of strain rate on the tensile properties of glass/epoxy, carbon/epoxy and hybrid (glass-carbon/epoxy) composites are experimentally and theoretically investigated in the range of strain rates from 0.0016 s −1 to 542 s −1 . Drop mass setup is used for high strain rate tests. Quasi-static tests are performed on Instron universal testing machine in accordance with ASTM D638 . The results indicate that the tensile strength and tensile modulus of GFRP and hybrid composites increase and percentage of failure strain for GFRP, CFRP and Hybrid composites decreases with the increase in strain rate, whereas tensile strength and tensile modulus of CFRP composites remains approximately constant. The scanning electron microscopy is used for analyzing the failure modes of the failed region (surface) of the tested specimens. Non contact DIC system is used to capture the strain field with the help of high speed camera.

Airport Runway Debris Edge Detection Algorithm

Airport runway debris detection decides security of plane and passengers. The relative merits of the various types of sensor and the effects of adverse environmental conditions on their performance, a novel fuzzy weighted morphology algorithm of detection about runway debris is approved. The experimental results show that the proposed algorithm, compared with a few classic algorithms of edge detection, which can achieves the image edge precisely and reduce noises, better retain the image details, and adaptively detect the complete and successive edges.

Optimization of composite plates subjected to buckling and small mass impact using lamination parameters

The small mass impact, such as runway debris and dropped tools, is a major issue during the design of composite plates, as it may significantly reduce the plate strength and stiffness without any visible damage. This work presents a novel optimization procedure to maximize the critical buckling load of composite plates subjected to small mass impact considering impact response and delamination threshold load predicted by closed forms solutions. The optimization is based on lamination parameters combined with laminate databases. In the first phase of the optimization a simplified model is used to obtain an approximate optimum. A design optimization using refined finite element model starting from the previous phase optimum is performed. The proposed algorithm is efficient, robust and applicable to many optimization problem for composite plates.

Runway debris impact threat maps for transport aircraft

AbstractLarge transport aircraft are particularly susceptible to impact damage from runway debris thrown up by the landing gear. A methodology was developed to predict the trajectories of stones lofted by the nose wheel and subjected to aerodynamic forces due to the wake behind the nose landing gear and beneath the aircraft. In conjunction with finite element modelling of the stone/ground/tyre contact mechanics, an analytical model was used to perform a stochastic prediction of the trajectories of runway stones to generate impact threat maps which showed the relative likelihood of stones impinging upon various areas on the underside of a C-130 Hercules. The impact envelopes for the C-130 extended three to eighteen metres behind the nose wheel and two metres either side of the centre of the aircraft. The impact threat maps were especially sensitive to the values of the coefficients of lift and drag acting on the stone during its flight.

A multimodal sensor system for runway debris detection

For foreign object detection on runways, highly sensitive radar sensors give the opportunity to detect even very small objects, metallic and non-metallic, also under adverse weather conditions. As it is desirable for airport applications to install only small but robust installations along the traffic areas, millimeter-wave radars offer the advantage of small antenna apertures and miniaturized system hardware. A 220-GHz radar was developed, which is capable to serve this application, if several of these are netted to cover the whole traffic area. Although under fortunate conditions the radar allows a classification or even an identification of the debris, the complete system design incorporates 3-D time-of-flight cameras for assistance in the identification process, which are also distributed along the traffic areas. The system approach further relies upon a change detection algorithm on the netted information to discriminate non-stationary alarms and reduce the false alarm ratio.

Numerical Study on Impact Response of Aircraft Sandwich Wing Made of Fiber-Metal Laminate Face-Sheets Subjected to Bird Strike

Aircraft structures are frequently subjected to impacts from objects such as runway debris and birds. In new aircraft structural design, Fiber Metal Laminates (FMLs) play a significant role due to their excellent mechanical properties, particularly the impact properties. In this study, the aircraft sandwich wing with FML face-sheets are analyzed by finite element model for simulating the bird strike. The numerical simulations of bird strike impact are performed adopting a lagrangian approach to design the wing by MSC/PATRAN FE code. The numerical obtained results are compared with the results in the literature for validation of the model. The effect of fiber orientations, fiber types, metal types in FML face sheets in sandwich wing on impact responses are investigated. The impact responses are illustrated by displacement history, contact force history and energy absorption. According to these results, the sandwich panel with FML skin is suitable structure for energy absorption (that is the most important factor in impact phenomena). The lay-ups with titanium metal layer with aramid fibers are the best.

면내하중을 받는 복합적층판에 대한 충격하중 및 음향 해석

The potential hazards resulting from a low-velocity impact(bird-strike, tool drop, runway debris, etc.) on aircraft structures, such as engine nacelle or leading edges has been a long-term concern to the aircraft industry. Certification authorities require that exposed aircraft components must be tested to prove their capability to withstand low-velocity impact without suffering critical damage. In most of the past research studies unloaded specimens have been used for impact tests, however, in reality it is much more likely that a composite structure is exposed to a certain stress state when it is being impacted, which can have a significant effect on the impact performance. And the radiated impact sound induced by impact is analyzed for the damage detection evaluation. In this study, an investigation was undertaken to evaluate the effect in-plane loading on the impact force and sound of composite laminates numerically.