Low-energy Impact Research Articles

Damage Resistance of Honeycomb Sandwich Composites under Low-Energy Impact

Damage Resistance of Honeycomb Sandwich Composites under Low-Energy Impact

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.

Electron-impact ionization of water molecules at low impact energies.

The electron-impact ionization of water molecules at low impact energies is investigated using a theoretical approach named M3CWZ. In this model, which considers exchange effects and post-collision interaction, the continuum electrons (incident, scattered, and ejected) are all described by a Coulomb wave that corresponds to distance-dependent charges generated from the molecular target properties. Triple differential cross-sections for low impact energy ionization of either the 1b1 or 3a1 orbitals are calculated for several geometrical and kinematical configurations, all in the dipole regime. The M3CWZ model is thoroughly tested with an extensive comparison with available theoretical results and COLTRIMS measurements performed at projectile energies of Ei = 81eV [Ren et al., Phys. Rev. A 95, 022701 (2017)] and Ei = 65eV [Zhou et al., Phys. Rev. A 104, 012817 (2021)]. Similar to other theoretical models, an overall good agreement with both sets of measured data is observed for the angular distributions. Our calculated cross-sections' magnitudes are also satisfactory when compared to the other theoretical results, as well as to the cross-normalized relative scale data at 81eV impact energy. The 65eV set of data, measured on an absolute scale, offers a further challenging task for theoretical descriptions, and globally the M3CWZ performs fairly well and comparably to other theories. The proposed approach with variable charges somehow allows to capture the main multicenter distortion effects while avoiding high computational costs.

Cumulative damage characteristics of rock samples under cyclic low energy inclined plane impact

The ore pass wall in underground mines is often damaged by the impact and wear caused by unloaded ores. Studying the mechanisms of rock damage and failure under different impact angles can provide technical insights for the design and maintenance of the ore passes. This study employed an inclined impact experimental device along with a drop hammer loading test machine to perform cyclic low-energy impact tests on sandstone samples at five different inclined plane angles. The porosity of the rock samples was measured using a nuclear magnetic resonance (NMR) detection system, which provided data on porosity, T2 spectrum distribution, and NMR images of the samples after different numbers of impacts at different slope angles. The results indicate that: (1) Under cyclic inclined plane impact loading, an increase in the inclination angle, leads to reduced damage to the rock sample. The rock sample impacted at a 45° inclined plane exhibited the most severe damage. Rock samples with large inclination angles are more prone to experience rupture fractures at the tip of the inclined plane, primarily due to shear-tensile failure. The porosity changes dramatically at initially slope angles, resulting in greater damage. (2) As the number of impacts increases, the porosity of the samples first decreases, then increases, and subsequently decreases again. This progression corresponds to the closure of large pores following the first impact, followed by the expansion of micropores into macropores after 5 impacts, ultimately leading to gradual degradation of the samples until failure. (3) As the number of impacts increases, new cracks form within the rock sample and small cracks expand. Despite an increase in the number of micropores, the macropores still exert a significant influence on the rock samples, with the macropore spectrum area accounting for over 95%.

Temperature dependence of the deformation behavior and mechanical properties of a Fe–Mn–Al–C low-density steel for cryogenic application

The temperature dependence of the deformation behavior and mechanical properties of a Fe–20Mn–6Al-0.6C-0.15Si austenitic low-density steel was studied by tensile test and Charpy impact test at −196 °C, −77 °C and room temperature (RT), followed by microstructure analyses. The results indicate that the decreased tensile temperature, which is corresponding to reduced stacking fault energy (SFE), promotes the planar glide of dislocations. This led to larger fraction of low-angle grain boundaries (LAGBs) at lower tensile temperature. Consequently, both the tensile strength and elongation were improved as temperature decreased. At lower impact test temperature, the load and energy of crack initiation were larger, indicating a higher resistance to crack initiation. However, the transition from stable to unstable crack propagation occurred more rapidly at lower temperature, resulting in lower crack propagation energy and reduced resistance to crack propagation. This is because less region experienced planar glide. Due to the rapid unstable crack propagation, the Charpy absorbed energy at −196 °C was the lowest. The smaller fracture surface area, larger fibrous zone and more obvious ductile fracture characteristics in radial zone suggest that the toughness is better at higher temperature. Additionally, the presence of secondary cracks at RT delayed fracture, therefore benefitting toughness.

Absolute cross section for the unfolded lowest-lying triplet excitation in ammonia by low-energy electron impact

We report the first quantitative differential and integral cross sections (DCSs and ICSs) for the unfolded lowest-lying triplet and singlet transitions near threshold energies in ammonia molecule by electron impact at 9.8, 12, and 15 eV for the scattering angles of 10° to 130°. The DCS are shown to be typical of forward scattering for the singlet and isotropic for the triplet transitions, respectively. Toward the threshold energy, the ICS for the singlet state exhibits a monotonically decreasing feature, whereas a sharp increase is expected for the triplet state, which are compared with the R-matrix calculations from the literature.

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.

Phase transformation process and toughening mechanism of 12Cr1MoV heat-resistant steel for high-pressure boilers by external shower and internal spray heat treatment

To optimize the heat treatment process for 12Cr1MoV heat-resistant steel, this study designed a novel process of external shower and internal spray (ESIS), followed by air cooling. This new approach was simulated in the laboratory. The study focused on the variation in impact energy and the microstructural changes in the experimental steel subjected to different processes, specifically the T890 and T740 processes (where the numbers represent the termination temperature of ESIS). The phase transformation processes and toughening mechanisms of the steel after these treatments were thoroughly investigated. The theoretical analysis revealed that the microstructures of T890 and T740 steels consist of quasi-polygonal ferrite (QPF), granular bainite (GB), and pearlite. The QPF in T890 steel forms at a higher temperature compared to T740 steel, leading to a lower dislocation density and carbon content in QPF during the subsequent cooling phase. This results in the QPF in T890 steel having a hardness of 1.02 GPa lower than that of the QPF in T740 steel. The higher hardness of QPF in T740 steel correlates with reduced toughness and resistance to crack propagation. Under impact loading, the QPF in T740 steel exhibits insufficient crack propagation resistance to counteract the effects of microscopic defects within the tensile stress region of the fracture. Consequently, cracks preferentially propagate within the QPF, creating a relatively flat propagation path. In comparison, the fracture of T740 steel demonstrates a straighter propagation path in the tensile stress region than T890 steel, resulting in significantly lower impact energy for T740 steel.

Effect of Annealing Time on Various PtNi/C Binary Alloy Catalysts for ORR in PEFCs

Polymer electrolyte fuel cells (PEFCs) are used in automotive power supplies due to their advantages of low environmental impact and high energy conversion efficiency. However, Pt used for electrocatalysts is expensive and its activity and durability are problematic. In this study, the PtNi/C catalysts were prepared with different annealing times and the oxygen reduction reaction activity was evaluated. The linear sweep voltammograms and current-voltage curves showed that the PtNi/C catalysts annealing time for 60 min performed better than the commercial catalyst. This would be attributed to the internal alloying of Ni and better electronic structure due to the longer annealing time.

Defect induced heavy meson dynamics in the QCD conformal window

Upon introducing a heavy quark in the perturbative regime of the QCD conformal window we precisely determine the associated heavy meson spectrum and wave functions in terms of the number of light flavors and mass. We then compute the conformal Isgur-Wise function which is a central quantity in heavy quark physics. We further determine the impact of the residual low energy confining dynamics on the heavy meson spectrum. As a working framework, we adapt the heavy quark effective theory to the perturbative conformal window dynamics. Our work lays the foundations to systematically go beyond the infinite mass defect approximation in conformal field theories. Published by the American Physical Society 2024

β-Grain refinement in WAAM Ti-6Al-4 V processed with inter-pass ultrasonic impact peening

As-deposited Wire-Arc Additive Manufactured (WAAM) Ti-6Al-4V parts typically contain large columnar β-grains on a centimetre scale, with a strong 〈001〉 fibre texture, leading to anisotropic mechanical properties and unacceptable scatter in damage tolerance. Inter-pass deformation, introduced by the application of Ultrasonic Impact Peening (UIP) across each added layer, has been shown to be effective in refining the β-grain structure and achieving a weaker texture. The depth of deformation and the grain refinement mechanism induced by UIP have been investigated by combining advanced electron backscatter diffraction (EBSD) characterization with a ‘stop action’ observation technique. UIP facilitates a similar refinement mechanism and nearly the same depth of deformation as conventional machine hammer peening, with the advantages of a much higher strain rate, lower peak force, and two orders of magnitude lower impact energy, making it a faster and more economical process. β recrystallization is seen within the deformation zone during re-heating through the α → β transition. Although new recrystallized β-grains formed in the UIP surface-deformed layer to a shallower depth than that of remelting, recrystallization initiated ahead of the melt pool and the recrystallized grains grew downwards to a greater depth before remelting. These refined grains were thus able to survive and act as nucleation sites at the fusion boundary for epitaxial regrowth during solidification, greatly refining the grain structure.

Exploring the catastrophic regime: thermodynamics and disintegration in head-on planetary collisions

ABSTRACT Head-on giant impacts (collisions between planet-sized bodies) are frequently used to study the planet formation process as they present an extreme configuration where the two colliding bodies are greatly disturbed. With limited computing resources, focusing on these extreme impacts eases the burden of exploring a large parameter space. Results from head-on impacts are often then extended to study oblique impacts with angle corrections or used as initial conditions for other calculations, for example, the evolution of ejected debris. In this study, we conduct a detailed investigation of the thermodynamic and energy budget evolution of high-energy head-on giant impacts, entering the catastrophic impacts regime, for target masses between 0.001 and 12 M$_{{\oplus }}$. We demonstrate the complex interplay of gravitational forces, shock dynamics, and thermodynamic processing in head-on impacts at high energy. Our study illustrates that frequent interactions of core material with the liquid side of the vapour curve could have cumulative effects on the post-collision remnants, leading to fragmentary disintegration occurring at lower impact energy. This results in the mass of the largest remnant diverging significantly from previously developed scaling laws. These findings suggest two key considerations: (1) head-on planetary collisions for different target masses do not behave similarly, so caution is needed when applying scaling laws across a broad parameter space; and (2) an accurate model of the liquid-vapour phase boundary is essential for modelling giant impacts. Our findings highlight the need for careful consideration of impact configurations in planetary formation studies, as head-on impacts involve a complex interplay between thermodynamic processing, shocks, gravitational forces, and other factors.

Experimental and Simulation Study on Failure of Thermoplastic Carbon Fiber Composite Laminates under Low-Velocity Impact.

Numerous studies have demonstrated that under low-velocity, low-energy impact conditions, although the surface damage to fiber-reinforced composite laminates may be minimal, significant internal damage can occur. Consequently, a progressive damage finite element model was specifically developed for thermoplastic carbon fiber-reinforced composite laminates subjected to low-speed impact loads, with the objective of analyzing the damage behavior of laminates under impacts of varying energy levels. The model utilizes a three-dimensional Hashin criterion for predicting intralayer damage initiation, with cohesive elements based on bilinear traction-separation law for predicting interlaminar delamination initiation, and incorporates a damage constitutive model based on equivalent displacement to characterize fiber damage evolution, along with the B-K criterion for interlaminar damage evolution. The impact response of laminates at energy levels of 5 J, 10 J, 15 J, 20 J, and 25 J was analyzed through numerical simulation, drop-hammer experiments, and XCT non-destructive testing. The results indicated that the simulation outcomes closely correspond with the experimental findings, with both the predicted peak error and absorbed energy error maintained within a 5% margin, and the trends of the mechanical response curves aligning closely with the experimental data. The damage patterns predicted by the numerical simulations were consistent with the results obtained from XCT scans. The study additionally revealed that the impact damage of the laminates primarily stems from interlaminar delamination and intralayer tensile failure. Initial damage typically presents as internal delamination; hence, enhancing interlaminar bonding performance can significantly augment the overall load-bearing capacity of the laminate.

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

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. We aim to systematically characterize the spectral variability of surface iron-rich olivine in the space weathering environments of Phobos and the Moon. 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. We find that olivine with higher Fe content undergoes stronger weathering under the same irradiation energy, shifting absorption centers around 1.08 mu m and 1.35 mu m 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 mu m under various irradiation levels, while the band center around 1.35 mu m remains stable. 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 mu m is a good indicator of the Mg$\#$ value of space-weathered olivine.

Comparison study of Izod impact properties on 3D printed thermoplastic and thermoset carbon fiber composite at different infill density

PurposeThis study aims to evaluate the low energy impact characteristics of 3D printed carbon fiber thermoplastic and thermoset polymer composite using the Izod impact test. The effects of infill density are examined on the Izod impact properties of 3D printed thermoset polymer and thermoplastic composite specimens. Furthermore, a thorough investigation is conducted into the effect of heat treatment using a hot-air oven on both types of 3D printed composite specimens. To characterize the impact characteristics of each specimen, the fracture surfaces caused by impact load are inspected, and the fracture mechanism is studied using scanning electron micrographs.Design/methodology/approachIzod Impact specimens of thermoset (epoxy resin) and thermoplastic carbon fiber of different infill density (70, 75, 80, 85, 90 and 100%) are fabricated using the different fiber impregnation 3D printing process. To carry out the heat treatment process, printing of composites is done for each infill design from both thermoset and thermoplastic composites and the impact characteristics of specimens are evaluated on a pendulum test-rig using the ASTM D-256 standard. Using a scanning electron microscope, each fracture zone underwent four separate scanning processes, ranging in size from 2 µm to 100 µm.FindingsThe impact resistance of the 3D printed thermoset and thermoplastic composite material is significantly influenced by the type of fiber placement and infill density in the matrix substrate. Because of the weak interfacial strength between the layers of fiber and polyamide 6, the specimen printed with continuous fiber implanted at the part exhibited reduced impact resistance. At 75% infill density, the impact specimen printed with coextruded fiber showed the highest impact resistance with a 367.02% greater magnitude than the continuous fiber specimen with the same infill density.Originality/valueThis work presents a novel approach to analyze the low energy impact characteristics and three-dimensional printing of carbon fiber reinforced thermoplastic and carbon fiber reinforced thermoset and thermoplastic composite material.

Prediction of low-velocity impact mechanical response and damage in thermoplastic composites considering elastoplastic behavior

By incorporating the plastic deformation and Puck damage criteria law, a three-dimensional elastic-plastic-damage model has been established to predict the behavior of carbon fiber reinforced thermoplastic (CFRTP) composites under low-velocity impacts. The model has been integrated into ABAQUS/Explicit, and off-axis tensile test were conducted to ascertain appropriate parameters for the elastic-plastic model. Additionally, finite element modeling of off-axis tensile were employed to assess the precision of the model parameters and to contrast the variance of accounting for plastic deformation against neglecting it. The effectiveness of the elastic-plastic-damage model, incorporating damage considerations, was confirmed through an analysis of the mechanical response and progressive damage of CFRTP during low-velocity impact tests. Compared to the elastic-damage model that does not consider plastic deformation, the elastic-plastic-damage model, which takes plastic deformation into account, exhibits higher prediction accuracy. Both simulation and experimental results indicate that delamination and matrix cracking are the dominant damage patterns observed in CFRTP at relatively low impact energies (≤16.20 J).

Nondestructive Evaluation and Residual Property Assessment of Impacted Nylon/carbon-Fiber Additively Manufactured FFF Components Using Four-Point Bend and Ultrasonic Testing

ABSTRACT Fusion-based material extrusion additive manufacturing, commonly known as fused filament fabrication (FFF), is a layer-by-layer manufacturing process known for creating custom components, specializing in complex geometries, with applications in the aerospace, automotive, medical, as well as many other industries. Due to the critical nature of these industries, it is imperative to understand the relationship between the AM material in question, the nature of the resultant damage, and the impact of these two parameters on the future performance of the component. The purpose of this study is to investigate the relationship between low-velocity impact and the resultant damage in common functional FFF materials and to develop methods of visualizing that damage using ultrasonic nondestructive evaluation. Coupons of a nylon feedstock infused with and without 10% chopped carbon fiber were fabricated using an Essentium HSE printer and impacted at various energies. The extent of the damage was visualized using ultrasonic testing (UT), in which significant internal cracking was observed. Four-point bend testing was utilized to compare behavior of the material prior to impact at a lower impact energy (3J), and a higher impact energy causing visual fracture (7J). X-ray CT was also performed on two samples to validate UT findings.

Viscoelasticity and impact behaviour of green epoxy bio-composites made of date palm leaflets

Natural fibres can replace traditional synthetic fibre composites in applications for which sustainability is a critical aspect. Elghas date palm leaflets in their natural state and with handwoven fabric reinforcements—the latter from customary and regional carpet productions—are included into new bio-based composites that are produced and characterized in this work. The two classes of bio-composites have the same weight fraction in terms of reinforcement. The date palm leaflets reinforcements are dispersed in a green resin matrix. Bio-composites reinforced with leaflets tree have twice the static bending strength than those with leaflets fabric reinforcements. The viscoelastic behaviour of those bio-composites shows an opposite trend, with the laminates reinforced with leaflets fabric being the least sensitive. For an impact energy of 3 J, the strength of bio-composites with leaflets fabric is double than the analogous value shown by bio-composites with leaflets tree. The impact strength however increases by 4.7 times for lower impact energies of 1 J. The results shown here further demonstrate the possibility of developing bio-composites from agro-industrial products, waste, and local textile traditions for secondary structural applications.

EOR Technology (Patents) and Science (Articles) Assessment of BRICS and nonBRICS with Growth Rates and Specializations within Responsible Global Energy Transition: A Critical Review

To achieve a low-carbon energy transition, it is essential to ensure that, as long as fossil fuels are needed, their production is sustainable, minimizing the environmental impact and securing resources for advancing greener technologies, in alignment with SDGs 7, 13, and 14. Enhanced oil recovery (EOR) increases the recovery rates without new developments. The recent expansion of the BRICS consortium, involving major producers, underscores the need to evaluate their EOR technologies, particularly potential gaps that could hinder global energy transition strategies. We analyzed intermediate levels of technological readiness levels (TRLs) utilizing patents (TRL4-5) and articles (TRL3) for 18 EOR methods between 2002 and 2021. Composite indicators derived from patents including compound annual growth rate, specialization, concentration, diversification, and Gini inequality were employed. Both BRICS and nonBRICS exhibited analogous distributions in the articles (particularly Norway, United Kingdom, Canada) and patents (particularly Russia, China, and Ukraine). The decline in growth rates among BRICS and negative rates in nonBRICS suggest a technological plateau for traditional methods. However, environmentally low-impact EOR methods are experiencing exponential emergence (low salinity water, MEOR, polymers and macromolecular compounds, their associations with surfactants, and WAG). Both groups are self-sufficient in EOR, ensuring a responsible and low-impact energy transition. This ensures energy quality while facilitating the maturation of renewable technologies.

Low energy impact damage characteristics of epoxy coating on the surface of sandwich composites

AbstractWhen composite honeycomb sandwich structures are subjected to low energy impacts, the upper panel or the honeycomb core often suffers large damages, which are invisible, but affects the structural safety. To achieve non‐destructive detection of these damages, an epoxy resin film (ERF) was designed as a functional coating to display the internal failure features on structure surface. The effect of low energy impacts on the damage modes of the ERF was first investigated, and then the correspondence between the ERF damage characteristics and the structural internal failure was established. Simulation and experimental results showed that with the increase of impact energy, cracks on the ERF expanded from the radial radiation with a small extension range to the circumferential pattern with an increased damage area. Meanwhile, localized delamination appeared inside the upper panel, while the degree of flexure and crushing damage to the core continued to increase. Based on the analysis of the crack extension pattern of the ERF and the damage state of the upper panel and honeycomb core, a specific link between the ERF crack characteristics and the internal damages to the sandwich structure was obtained, which might offer a novel non‐destructive testing method for composite impact damages.Highlights Low energy impact damage in honeycomb sandwich structures was a concern. Impact damage response of epoxy resin film on sandwich composites was studied. Crack extension of the film showed a particular change from radial to annular. Specific link between film crack and sandwich structure damage was established. The results would be helpful for damage detection in sandwich composites.