High Impact Energy Research Articles

Standardization of high-energy laser impact tests with respect to temperature, reflection and perforation time

Abstract High-energy laser impact tests on identical materials and irradiation parameters often show deviating results between different testing institutes. This particularly affects the specular component of the reflection and the temperatures. Even the supposedly easy-to-determine perforation time sometimes shows large variations between different test institutes. For a reliable and reproducible determination of test results, a standardization of the experimental setups is necessary. Test results using two different reference materials are presented. These tests demonstrate that standardizing experimental setups and evaluation methods significantly reduces the deviations of the experimental results. The presented multi-institutional approach aims at gaining data of laser reflection, temperature, and perforation time of laser impacted samples, and at developing an optimized experimental setup based on different existing laboratory equipment and experimental approaches.

High‐velocity impact response and damage behavior of bio‐inspired helicoidal composite laminates: Experimental and numerical investigation

AbstractBio‐inspired helicoidal composite laminates have been found to have better impact resistance and energy absorption than conventional laminates. To study the impact responses and damage behaviors of bio‐inspired helicoidal composite laminates under high‐velocity impact, the composite laminates with three helix angles were designed and tested. Two types of light‐gas gun were used to provide low and high impact energies, the velocity was measured using a velocimeter and the damage to the laminate profile was observed by scanning electron microscopy. Numerical simulation is then used to simulate the damage behavior of the helicoidal laminates based on the Hashin failure criterion and the revised dynamic increase factor. The results show that: under an impact of low energies, the helicoidal mechanism serves to absorb the impact energy through the generation of additional delamination. The laminates with the helix angle of 15° exhibits the maximum delamination area and the minimum residual velocity. However, under the impact of higher energies, the helicoidal mechanism is unlikely to improve the energy absorption and will inhibit the delamination damage. The laminates with the helix angle of 45° have the greatest inhibitory effects on delamination damage, with a delamination area reduction of 35.41%. Due to these differences, therefore, the use of helicoidal laminates should be more cautious in high‐velocity impact resistance and better avoid high‐energy situations. These findings can support the design of novel impact resistance structures.Highlights High‐velocity impact tests and FEM simulation of helicoidal laminates are carried out Damage behaviors and failure mechanism of helicoidal laminates are studied Delamination and fiber breakage are the main failure modes The laminates with the helix angle of 15° has the best impact resistance.

Synchronous enhancement of safety protection and impact perception in intelligent leather

High protection performance and intelligence are gradually becoming indispensable key factors with the ever-improving personal protective equipment. However, protective material that can not only resist but also percept full type of impacts is an urgent need due to complex combat scenarios. This work reports an intelligent leather/shear stiffening gel (SSG)/Kevlar-shear thickening fluid (STF)/non-woven fabric (LSKSN) composite, which exhibits superior and comprehensive impact resistance performance in needle puncture, knife puncture, ballistic impact, and blunt impact. Especially, the LSKSN composite not only improves the puncture resistance performance by 71% but also still maintains a large resistance after being punctured. Moreover, the LSKSN composite possesses a high limit penetrated velocity of 159 m s−1 and can dissipate a high impact energy of 24.6 J, causing the bulletproof to be improved by 22%. Due to the excellent force-buffering performance and rate-dependent energy dissipation characteristics in wide-impact energy, the maximum energy dissipation rate of the LSKSN composite reaches 95%. Simultaneously, the further developed electronic LSKSN (E-LSKSN) composite shows outstanding perceptual capability, which is sensitive to various impacts and can accurately identify the impact types through different resistance changes (10–8000%) and response times (0.1–100 ms). Finally, based on the bending sensing and impact sensing properties of the E-LSKSN composite, a wireless signal transmission system is constructed to monitor the safety and movement status of the human body in real-time, which demonstrates this LSKSN composite possesses high potential in the next generation of intelligent protective equipment.Graphical

The Protection of RC Columns by Bio-Inspired Honeycomb Column Thin-Walled Structure (BHTS) Under Impact Load.

The bio-inspired honeycomb column thin-walled structure (BHTS) is inspired by the biological structure of beetle elytra and designed as a lightweight buffer interlayer to prevent damage to the reinforced concrete bridge pier (RCBP) under the overload impact from vehicle impact. According to the prototype structure of the pier, a batch of scale models with a scaling factor of 1:10 was produced. The BHTS buffer interlayer was installed on the reinforced concrete (RC) column specimen to carry out the steel ball impact test. Then, the modified numerical model was subjected to the low-energy input impact test of the steel ball without energy loss during the falling process at the equivalent height of 1.0-3.5 m, and the dynamic response characteristics of the RC column were analyzed. By comparing the impact force and impact duration, maximum displacement, and residual displacement in the impact model, the BHTS buffer interlayer's protective effect on RC columns under lower energy lateral impact was evaluated. Later, a high-energy input lateral impact test of a steel ball falling at an equivalent height of 20.0 m was carried out. According to the material damage, dynamic response, and energy absorption characteristics in the impact model, the failure process of the RC columns was analyzed. The results showed that BHTS absorbed 82.33% of the impact kinetic energy and reduced 77.27% of the impact force, 86.51% of the inertia force, and 64.86% of the base shear force under the failure mode of a 20 m impact condition. It can transform the shear failure of the RC column into bending failure and play an effective protective role for the RC column. This study can provide useful references for collision prevention design in practical engineering.

Resisting High-Energy Impact Events through Gap Engineering in Superconducting Qubit Arrays

Quantum error correction (QEC) provides a practical path to fault-tolerant quantum computing through scaling to large qubit numbers, assuming that physical errors are sufficiently uncorrelated in time and space. In superconducting qubit arrays, high-energy impact events can produce correlated errors, violating this key assumption. Following such an event, phonons with energy above the superconducting gap propagate throughout the device substrate, which in turn generate a temporary surge in quasiparticle (QP) density throughout the array. When these QPs tunnel across the qubits’ Josephson junctions, they induce correlated errors. Engineering different superconducting gaps across the qubit’s Josephson junctions provides a method to resist this form of QP tunneling. By fabricating all-aluminum transmon qubits with both strong and weak gap engineering on the same substrate, we observe starkly different responses during high-energy impact events. Strongly gap engineered qubits do not show any degradation in T1 during impact events, while weakly gap engineered qubits show events of correlated degradation in T1. We also show that strongly gap engineered qubits are robust to QP poisoning from increasing optical illumination intensity, whereas weakly gap engineered qubits display rapid degradation in coherence. Based on these results, gap engineering mitigates the threat of high-energy impacts to QEC in superconducting qubit arrays. Published by the American Physical Society 2024

Erosion enhancement by impurity entrainment in the highly collisional plasmas of Magnum-PSI

Abstract Extrinsic impurity seeding is planned for ITER to avoid high heat fluxes to the tungsten divertor targets. Nevertheless, excessive sputtering by impurities would lead to a reduction in fusion power output and divertor lifetime. Unlike today's fusion devices, the entrainment of impurities is expected to play an increasing role in ITER's highly collisional near-surface plasma. Impurity entrainment refers to the acceleration of impurities with the plasma flow by collisional drag, leading to elevated impact energies. To investigate impurity entrainment under ITER-like plasma conditions ($n_e > 2 \cdot 10^{20}$ m$^{-3}$, $T_e <$ 5 eV), argon-seeded hydrogen plasmas were formed with the linear plasma generator Magnum-PSI. Doppler shifts in spatially-resolved emission profiles of argon (Ar II - 480.6 nm) and hydrogen (H$_\mathrm{\beta}$ - 486.1 nm) reveal the entrainment of seeded argon towards the upstream hydrogen velocity ($\sim$9 cm from surface), corresponding to $\sim$0.39 of the common-system sound speed. In addition, the sputtering yield of tungsten by argon bombardment for the argon-seeded hydrogen plasma was compared to a pure argon plasma by monitoring tungsten (W I - 400.9 nm) emission. These sputtering experiments indicate further entrainment of the argon impurities to $\sim$0.65 of the common-system sound speed at the sheath edge, leading to a large increase in their impact energy. Extrapolation of the Magnum-PSI results to ITER, using existing SOLPS-ITER simulations to determine the divertor plasma conditions, indicates more than an order of magnitude increase in gross erosion of the divertor targets due to impurity entrainment. However, the net erosion rate could still be kept under control if high re-deposition rates are achieved, which is treated in the companion paper \cite{Cornelissen2023}. The combination of a low sputtering threshold energy and high impact energy of impurities constrains the fine balance between radiative cooling with impurity seeding and avoiding extensive divertor erosion.

High impact resistance and energy absorption composite reinforced via shear thickening gel/angle interlocking for flexible wearable protective

The study reveals the combination of shear thickening gel (STG) with angle interlocking fabrics with different thickness direction binding modes to prepare flexible composites. The effect of thickness direction binding modes on flexible composites' ballistic performance and failure mechanisms are systematically investigated. The results reveal that the bullet penetrates STG and yarn simultaneously during the impact phase, causing STG to produce the shear thickening effect. Flexible composites produce synergistic energy absorption. The layer-to-layer structure has a 4.49 % higher ballistic limit than the through-thickness structure, proving superior impact resistance. This investigation aims to enhance the design of lightweight ballistic composites by examining the failure mechanisms of flexible composites in response to ballistic impacts.

Additive manufactured 3D re-entrant auxetic structures for enhanced impact resistance

Abstract This study presents a novel exploration of the geometric parameters within a 3D re-entrant auxetic lattice structure, specifically focusing on their unique impact energy absorption properties, which were systematically evaluated through drop weight impactor testing. Each lattice configuration was additively manufactured using stereolithography, allowing for precise control over strut thickness (t), re-entrant angle (θ), and the aspect ratio (h/l) of unit cells during both low and high energy impact scenarios. This study found that the overall auxetic behavior is predominantly controlled by the aspect ratio of the cell ribs, while the modulus is governed by rib thickness. A finite element model was subsequently developed to simulate the experimental impact loading conditions and was used to examine a wider range of parameters that were not experimentally tested. The simulated dynamic test results displayed the deformation trends and changes to the Poisson's ratio. Among the studied parameters, experimental results highlighted that a lattice structure with t = 1.6 mm, θ = 65°, and a h/l ratio = 1.8 exhibited the highest specific energy absorption (SEA) under uniaxial impact deformation with 5 Joules of impact energy. Conversely, when employing 20 Joules of impact energy revealed the greatest SEA at t = 1.0 mm, θ = 65°, and an h/l ratio of 2.2. The results demonstrate unique deformation mechanism of auxetic structures under impact loading and the capacity to adapt the 3D re-entrant lattice structure for applications requiring tailored impact energy absorption.

Numerical modeling and experimental validation of low velocity impact of woven GFRP/CFRP composites

Low-velocity impact of 2D woven glass fiber reinforced polymer (GFRP) and carbon fiber reinforced polymer (CFRP) composite laminates was studied experimentally and numerically. Hybrid laminates containing blocked layers of GFRP/CFRP/GFRP with all plies oriented at 0° were investigated. Relatively high impact energies were used to obtain full perforation of the laminate in a low-velocity impact setup. Numerical simulations were carried out using the in-house transient dynamics finite element code, Sierra/SM, developed at Sandia National Laboratories. A three-dimensional continuum damage model was used to describe the response of a woven composite ply. Two methods for handling delamination were considered and compared: (1) cohesive zone modeling and (2) continuum damage mechanics. The reduced model size achieved by omission of the cohesive zone elements produced acceptable results at reduced computational cost. The comparison between different modeling techniques can be used to inform modeling decisions relevant to low velocity impact scenarios. The modeling was validated by comparing with the experimental results and showed good agreement in terms of predicted damage mechanisms and impactor velocity and force histories.

Research on the collision safety of battery packs with interlaced battery cell arrangement

Ensuring collision safety performance is imperative in battery pack layout design. Conventional battery pack configurations face challenges due to a single-load transfer path issue and disregard the inherent deformability of battery cells. To tackle these challenges and facilitate load dispersion for a wider distribution of collision energy absorption among battery cells, this study suggests a battery cell layout inspired by a biomimetic honeycomb structure. The research model utilizes a uniform battery model and directly encapsulates the batteries within the battery pack, aligning with current packaging trends and enabling interleaved arrangements. Through side pillar collision simulations, the study compared and analyzed aspects such as deformation intrusion of the battery pack, acceleration of deformation in the affected region, impact load transmission, and battery failure scenarios. The findings indicate that the interleaved arrangement offers additional load transmission paths, reducing battery pack deformation intrusion by over 3.8% and effectively optimizing the majority of vulnerable battery cells, leading to a decrease in battery cell damage by over 7.3%. This effect is particularly notable in high-energy impact areas where numerous battery cells surpass failure thresholds. Furthermore, analyses of impacts at various positions and angles demonstrate that the interleaved arrangement of battery packs significantly enhances collision safety performance, mitigating battery damage during collisions and providing valuable insights into battery pack layout design.

Experimental investigation the effect of bamboo micro filler on performance of bamboo-sisal-E-glass fiber-reinforced epoxy matrix hybrid composites

The numerous advantages of natural fiber reinforced hybrid composites, such as their light weight, biodegradability, recyclability, availability, and low cost, have brought them to the forefront for various structural applications in the automotive and aerospace industries. Aim of this study was to evaluate the impact of varying the weight fractions of bamboo micro filler on the tensile, flexural, impact, and water absorption properties of the Sisal-Bamboo-E-glass fiber reinforced epoxy matrix hybrid composite prepared by manual hand layup method. To enhance the bond between natural and synthetic fibers and reduce the hydrophilic nature of natural fibers, bamboo and sisal fibers were treated with 5 % NaOH for 6 and 8 h, respectively. The E-glass fiber content was kept constant at 10 %, while the weight fractions of sisal, bamboo fiber, epoxy matrix, and bamboo micro filler were varied. The bamboo micro filler size ranged from 75 to 100 μm. Tensile and flexural tests were conducted using a computer-controlled universal electromechanical testing machine, while impact testing was performed with a Charpy impact test machine. The results showed that the hybrid composite containing 15 % sisal, 10 % glass, 15 % bamboo fiber, 57 % epoxy, and 3 % bamboo micro filler exhibited the highest tensile strength (87 MPa),flexural strength (77 MPa), high impact energy (8.9 J) and high toughness (24.64 J/cm2). Conversely, the highest water absorption capacity was observed in composites with 6 % bamboo micro filler. Overall, the tensile, flexural, impact, and water absorption properties of the hybrid composites were significantly influenced by the weight fractions of the fibers and bamboo micro filler.

Direct Evidence of Breakdown of Spin Statistics in Ion-Atom Charge Exchange Collisions.

Recent experimental studies have questioned the validity of spin statistics assumptions, particularly in charge exchange processes occurring in atomic MeV collisions. Here, we study spin-resolved single electron capture processes in collisions between C^{3+} ions and helium within an energy range of 1.25-400 keV/u. Using high resolution reaction microscope and multielectronic theoretical approaches, we directly measure and calculate the true population information of the C^{2+}(1s^{2}2s2p ^{1,3}P) states at the time of electron capture, overcoming the previous experimental and theoretical difficulties. At the level of integral and scattering angle differential cross sections, our results demonstrate the breakdown of pure spin statistics arguments, especially at high impact energies where they are traditionally expected to be valid. These novel findings and conclusions raise intriguing questions both in the understanding of the electronic dynamics during such fast collisional processes and in exploring quantum manipulation of atomic and molecular reactivity.

Low-velocity impact response of hybrid sheet moulding compound composite laminates

This work presents a comprehensive study on the impact damage tolerance of Sheet Moulding Compounds (SMCs). The performance of glass, carbon and hybrid glass/carbon SMCs are compared by means of tensile, compression, low-velocity impact and compression after impact experiments. Damage analysis of the impacted laminates was performed by ultrasonic and X-ray methodologies. The glass SMC exhibited the highest damage tolerance in low-velocity impact with the smallest damaged area, crack density and loss in compression after impact (CAI) strength. On the other hand, the carbon SMC demonstrated superior in-plane stiffness and strength, but exhibited a large damaged area and crack density under impact. The hybrid SMC displayed an optimal compromise, exhibiting intermediate tensile in-plane performance and excellent damage tolerance at lower impact energy levels, but suffered from extensive delamination at the highest impact energy. Overall, the findings highlight the suitability of hybrid SMCs for structural applications with potential impact risks.

Synergy of high-intensity chromium ion implantation and ion beam energy impact on the zirconium alloy surface

The peculiarities and modes of material modification with high-intensity, high-power density ion beams on the irradiated surface are studied for the first time. Chromium ions are implanted into a zirconium alloy using a 25 kW/cm2, 450 μs beam at the pulse repetition rates within 8–35 pps. Every high-energy ion pulse impact is followed by ultrafast cooling of the surface due to heat removal into the target material. Three modes are studied at the temperatures of 580, 700, and 900 °C with an additional pulsed heating. An increase in the average target temperature from 580 to 700 °C within 1 h at the same pulse power density allows increasing the depth of chromium ion alloying from 1.5 to more than 7 μm. The use of ultrafast cooling of the Zr1%Nb alloy surface offers a grain size reduction from a few μm to approximately 50–250 nm, without any microstructural changes throughout the sample volume. An inhomogeneous chromium ion distribution over the target surface and depth is observed.

Displacement cascade bombardment of delta-hydrides in alpha-zirconium

One of the factors affecting the in-pile performance of Zr-based alloys is the precipitation of hydrides once H concentrations exceed the terminal solubility limit. H transport and hydride precipitation/dissolution is commonly modeled in codes such as BISON, but most of the experimental data supporting these models has been collected on unirradiated materials. As such, there is considerable uncertainty as to the influence of irradiation effects. In this work, molecular dynamics simulations of displacement cascades were performed on δ-hydrides to elucidate: 1) the extent of H dissolution following cascade impacts and 2) any alterations to defect production characteristics when compared to cascades in bulk Zr. The immediate amount of H dissolved in a high-energy cascade impact is notable, but a considerable fraction of the dissolved H atoms are rapidly re-absorbed into the hydride at reactor-relevant temperatures. The amount of dissolved H also decreases with increasing hydride size. When considering the expected volume fractions of hydrides, it is not expected that the irradiation-induced H dissolution rate will significantly affect the availability of H in the Zr lattice. In terms of defect production, cascades which overlap δ-hydrides produced an order of magnitude more stable defects than equivalent-energy cascades in bulk Zr. Vacancy defects are predominantly contained within the hydride structure while interstitials clusters are found adjacent to the hydride surface. Interstitials are strongly repelled by the hydride structure which may drive the expulsion of cascade-generated interstitials to the hydride surface and impede athermal recombination. Thus, the interatomic potential used in this work predicted a significant alteration to the defect survival efficiency and a stark production bias in the availability of mobile defects in bulk Zr following hydride-overlapped displacement cascades.

Near-infrared spectral behavior of space-weathered olivine with varying iron content

Context. Space weathering alters the surfaces of airless celestial bodies, thereby modifying their spectra significantly. Olivine plays a crucial role in responding to space weathering on silicate planets. However, the spectral variations that occur in olivine with varying iron content as a result of space weathering conditions remain unclear. Aims. We aim to systematically characterize the spectral variability of surface iron-rich olivine in the space weathering environments of Phobos and the Moon. Methods. We conducted nanosecond pulsed laser irradiation experiments on a set of synthetic Fe-rich olivine (Fa29, Fa50, Fa71, and Fa100). The energy levels were simulated for Phobos and the Moon. We analyzed the available near-infrared (NIR) spectroscopy. Results. We find that olivine with higher Fe content undergoes stronger weathering under the same irradiation energy, shifting absorption centers around 1.08 µm and 1.35 µm to longer wavelengths. When comparing the high energy and low frequency, spectral changes are more pronounced at low energy and high frequency. The olivine with the same iron content exhibits a more noticeable shift around 1.08 µm under various irradiation levels, while the band center around 1.35 µm remains stable. Conclusions. When the same amount of radiation energy is received, changes in the spectrum are more noticeable at low energy and high impact frequency than at high energy and low impact frequency. The absorption position at ~1.35 µm is a good indicator of the Mg# value of space-weathered olivine.

Low-velocity impact behavior and damage mechanisms of honeycomb sandwich structures with elastomeric interlayers in CFRP skins

Elastomers help improve the toughness of lightweight high-strength materials, offering significant potential for enhancing the mechanical properties. However, introducing elastomers into CFRP interlayers as skin for composite sandwich structures has not yet been explored regarding the impact responses of such novel structures. This paper, for the first time in literature studies the low-velocity impact behavior and damage mechanisms of this novel sandwich structure using a combined experimental and numerical approach. The experimental results of sandwich structures with and without elastomer layers under different impact energies are presented. Finite element models of the two sandwich structures are built and impact behaviors were compared. The differences in internal damage and energy distribution during the impact are investigated to explain the reasons for the differing impact responses of the two sandwich structures. The results reveal that elastomeric interlayers have a significant advantage in enhancing the damage resistance of composite sandwich structures, especially under high impact energy conditions. The key contributions of this paper include the experimental characterization of the impact behavior of composite sandwich structures with elastomeric interlayers, and the explanation of the reasons for the changes in impact responses caused by the elastomers from the perspectives of damage mechanisms and energy distribution.

Preparation, characterisation, physical, and compression testing of sucrose based closed-cell aluminium foam

ABSTRACT Aluminium foam can be used as a porous and lightweight material having comparatively high impact energy absorption. To reduce the death rate caused by collisions of vehicles, there is a need of analysing the crash-worthiness properties of materials. In this present work, the Aluminium foam was prepared using the powder metallurgy method for the crash-worthiness analysis. The Al6061 powder as a matrix material having particle sizes ranging from 5 to 30 µm and Sucrose particles as a space-holding material were mixed. The compaction process was done up to a pressure of 450 MPa to make the green compact and was further subjected to sintering up to a temperature of 500 °C for 1 hour resulting into the Aluminium foam. The compressive strength significantly decreased by 26.56%, 51.39%, 72.49%, and 64.34% approximately while volume fractions of sucrose particles varied as 20%, 30%, 40%, and 50%. On the other hand, the measured maximum porosity was found as 51.8% approximately in the Aluminium foam corresponding to the addition of 50% sucrose particles by volume. Out of all the examined samples, the foam developed by containing 20% (vol.) sucrose has exhibited the maximum strain energy absorption, specific energy absorption (SEA), and crushing force efficiency (CFE).

Use of Internal Bracing in Multi-ligamentous Knee Injury Reconstruction: A Systematic Review.

Multi-ligament Knee Injuries (MLKI) are often caused by a high-energy impact resulting in dislocation of the knee joint. Given the higher degree of instability associated with these MLKIs, surgical fixation with adjunctive internal bracing and the use of suture augmentation have been proposed with the intention of better restoring knee stability and improving the long-term outcomes of surgery. This systematic review seeks to appraise the current literature in relation to the role of internal bracing in the management of MLKI. All randomised control trials, observational studies, cohort studies, and cross-sectional studies containing patients with multi-ligamentous knee injuries managed with the use of internal bracing or suture tape augmentation were included in this review. The primary outcomes of interest were re-operation and failure rates, with secondary outcomes focussed on patient-reported outcome measures (PROMs) and examination findings of knee stability. 282 studies were identified for screening, 13 of which were suitable for inclusion and five of these had injuries with Schenck grade III or above. Of the studies identified, failure rates ranged from 0 to 13.6%. Lysholm score was the most commonly utilised PROM tool with scores ranging from 61.8 to 95. Stiffness requiring MUA ± adhesiolysis was a common complication identified across studies. The use of internal bracing in Multi-ligament Knee Injuries appears to be as effective as not using an internal bracing technique. The post-operative PROMs and relatively low failure rates reflect promising outcomes for the ongoing use of internal bracing in MLKI. However, further prospective studies directly comparing braced versus non-braced ligamentous repairs are required in order to definitively determine if the use of the internal brace does allow for increased joint stability and early rehabilitation.

Model testing of dynamic response of loess to impact load from helicopter landing

ABSTRACT To investigate the dynamic behaviour of loess under the impact loads of two tyres attached to a helicopter’s landing gear, a loading device capable of simultaneously applying dual impact loads was designed. A series of physical model tests, varying in impact energy and water content of the loess samples, were conducted. The study explored the settlement pattern, vertical dynamic stress distribution, and the effects of impact energy and water content. Results revealed that settlement in the shallow layer exhibits a characteristic W-shape, while the vertical dynamic stress time curve displays a single peak pulse. Settlement and vertical dynamic stress increase with higher impact energy. Increasing the water content of the loess sample results in greater settlement but lower vertical dynamic stress. For the simulated helicopter, when the tyre impact energy increases from 23.8 to 60.8 kJ, the resultant crater depth in loess with a moisture content of 16% increases from 7.6 to 18.1 cm, an increase of 11.5 cm. The peak vertical dynamic stress at a depth of 10 cm along the centerline of the tamper increases from 590.98 to 1449.4 kPa, more than doubling. These findings are valuable for the design of landing sites and landing gear systems.