Function Of Impact Energy Research Articles

Cracking of submerged beds

We investigate the phenomena of crater formation and gas release caused by projectile impact on underwater beds, which occurs in many natural, geophysical and industrial applications. The bed in our experiment is constructed of hydrophobic particles, which trap a substantial amount of air in the pores of the bed. In contrast to dry beds, the air–water interface in a submerged bed generates a granular skin that provides rigidity to the medium by producing skin over the bulk. The projectile's energy is used to reorganize the grains, which causes the skin to crack, allowing the trapped air to escape. The morphology of the craters as a function of impact energy in submerged beds exhibits different scaling laws than what is known for dry beds. This phenomenon is attributed to the contact line motion on the hydrophobic fractal-like surface of submerged grains. The volume of the gas released is a function of multiple factors, chiefly the velocity of the projectile, depth of the bed and depth of the water column.

Asteroid Impact Hazard Warning from the Near-Earth Object Surveyor Mission

NASA’s Near-Earth Object Surveyor mission, scheduled for launch in 2027 September, is designed to detect and characterize at least two-thirds of the potentially hazardous asteroids with diameters larger than 140 m in a nominal 5 yr mission. We describe a model to estimate the survey performance using a faster approach than the time domain survey simulator described in Mainzer et al. (2023). This model is applied to explain how the completeness for 5 and 10 yr surveys varies with orbit type and asteroid size and to identify orbits with notably high or low likelihoods of detection. Size alone is an incomplete proxy for impact hazard, so for each asteroid orbit, we also calculate the associated hazard based on the impact velocity and the relative likelihood of impact. We then estimate how effective the mission will be at anticipating impacts as a function of impact energy, finding that a 5 yr mission will identify 87% of potential impacts larger than 100 Mt (Torino-9, “Regional Devastation”). For a 10 yr mission, this increases to 94%. We also show how the distribution of warning time varies with impact energy.

Enhancing resistance to low-velocity impact of electrospun-manufactured interlayer-strengthened CFRP by using infrared thermography

This study investigates the effect of electrospun nylon nanofibres modification on the low-velocity impact resistance of carbon fibre reinforced polymer (CFRP) laminates. Integration of multiple excitation infrared thermography using advanced image processing techniques is used to characterize the damage as a function of impact energy. The results show an enhanced damage resistance for the modified specimens, which is also validated by force – displacement curves. The interlaminar cracks show a maximum reduction of 24.8%, while delaminated areas and defect depths experience reductions of up to 28.7% and 24.3%, respectively. Interestingly, thermal diffusivity is introduced to identify the damage shape successfully. Finally, a correlation study is conducted, and a novel damage prediction model based on thermal diffusivity is proposed for further quantitative analysis.

Experimental investigation on high-velocity impact damage and compression after impact behavior of 2D and 3D textile composites

This paper investigates the impact resistance and damage tolerance of 2D triaxially braided composites and 3D angle-interlock woven composites panels using high-velocity impact tests and compression after impact tests. Both materials present equivalent impact resistance with similar ballistic limit and energy absorption ratio. Nevertheless, the damage patterns of the two materials are quite different, among which, 2DTBC is characterized by global response and yarn debonding, while 3DAWC is characterized by localized damage without yarn debonding. However, in compression after impact tests, 3DAWC exhibits higher damage tolerance because the binder yarns resist buckling failure and kink bands formation during compression, resulting in higher residual compressive strength. In addition, how the damage morphology varies spatially due to the different deformation and damage modes caused by high-velocity impact is learned from X-ray CT scanning. Different from the relationship between impact energy and residual compressive strength pointed out by most research, this study also reveals a unique trend of residual compressive strength as a function of impact energy, considering both penetration and rebound conditions.

Precise damage shaping in self-sensing composites using electrical impedance tomography and genetic algorithms

Fiber-reinforced composites with nanofiller-modified polymer matrices have immense potential to improve the safety of high-risk engineering structures. These materials are intrinsically self-sensing because their electrical conductivity is affected by deformations and damage. This property, known as piezoresistivity, has been extensively leveraged for conductivity-based damage detection via electrical resistance change methods and tomographic imaging techniques such as electrical impedance tomography (EIT). Although these techniques are very effective at detecting the presence of damage, they suffer from an inability to provide precise information about damage shape, size, or mechanism. This is particularly detrimental for laminated composites which can suffer from complex failure modes, such as delaminations, that are difficult to detect. To that end, we herein propose a new technique for precisely determining damage shape and size in self-sensing composites. Our technique makes use of a genetic algorithm (GA) integrated with realistic physics-based damage models to recover precise damage shape from conductivity changes imaged via EIT. We experimentally validate this technique on carbon nanofiber (CNF)-modified glass fiber-reinforced polymer (GFRP) laminates by considering two specific damage mechanisms: through-holes (as a function of number, size, and location) and impact-induced delaminations (as a function of impact energy). Our results show that this novel technique can accurately reconstruct multiple through-holes with radii as small as 1.19 mm and delaminations caused by low velocity impacts. The reconstructed delamination shapes and sizes were shown to be in much better agreement with the actual delaminations observed using optical microscopy than is achievable by traditional EIT alone. These findings illustrate that coupling piezoresistivity with conductivity-based spatial imaging techniques and physics-based inversion strategies can enable damage shaping capabilities in self-sensing composite structures.

State-selective charge exchange cross sections in Be^{4+} -hbox {H}(2textit{lm}) collision based on the classical trajectory Monte Carlo method

A three-body classical trajectory Monte Carlo method is used to calculate the nl state-selective charge exchange cross sections in hbox {Be}^{mathrm {4+}}+ H(2lm) collisions in the energy range between 10 and 200 keV/amu. We present partial cross sections for charge exchange into hbox {Be}^{mathrm {3+}}(nl) (textit{nl} = 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f) states as a function of impact energy. Our results are compared with the previous classical and quantum-mechanical results. We show that the classical treatment can able to describe reasonably well the charge exchange cross sections.Graphic abstract

The effect of stacking sequence on the LVI damage of laminated composites; experiments and analysis

Results of a comprehensive experimental and computational low velocity impact (LVI) damage study are reported for T800s/3900-2B laminated composites with three stacking sequences. The stacking sequences studied are [0/45/0/90/0/−45/0/45/0/−45]s, [45/0/−45/90]3s, and [45/−45/0/45/−45/90/45/−45/45/−45]s, which are [50/40/10], [25/50/25] and [10/80/10] where each number indicates the percentage of zero, 45 and 90 plies. For each layup, three impact energy levels have been examined. After the LVI tests, the induced damage has been characterized with ultrasound C-scanning and high-resolution micro computed tomography (micro-CT). Computational predictions have been conducted using the enhanced Schapery Theory (EST) model. The numerical results are accurate in terms of the impact load responses and induced damage. The physics of the LVI damage of the samples with various stacking sequences and as a function of impact energy has been resolved using the EST model. The damage predicted by the EST model and the revealed damage mechanisms contribute to understanding the physics of the LVI behavior of laminated composites.

Rupture by impact-induced fatigue of a copper foil strip embedded in a multifunctional composite material

Multifunctional composite materials are highly sought-after by the aerospace and aeronautical industry but their performance depends on their ability to sustain various forms of damages, in particular damages due to repeated impacts. In this work we studied the mechanical behavior of a layered glass-epoxy composite with copper inserts subjected to fatigue under repeated impacts with different energy levels. Damage evolution as a function of impact energy was carefully monitored in order to determine the effect of the copper inserts on mechanical characteristics of the multifunctional composite, such as endurance and life. Results of repeated impact tests show that electric current interruption in the copper inserts occurs prior to the total perforation of the composite material, and after about 75% of the total number of impacts to failure. This is the case for the three energy levels considered in this study, [Formula: see text] = 2, 3 and 4 Joules. The epoxy resin was dissolved chemically in order to preserve the mechanical structure of the damaged copper inserts and the composite fibers for further inspection and analysis. Scanning electron microscopy (SEM) of the fractured copper inserts revealed interesting information on the nature of the damage, including information on plastic deformation, strain hardening, cracking mode, temperature increase during the impacts, and most importantly the glass fibers and their roles during the impact-fatigue tests.

Data for secondary-electron production from ion precipitation at Jupiter III: Target and projectile processes in H[formula omitted], H, and H[formula omitted] + H[formula omitted] collisions

To extend the range of data required for modeling the secondary-electron production from ion precipitation into the upper atmosphere of Jupiter, inelastic processes for collisions of 1 keV to 25 MeV H+, H, and H− with H2 are considered. As in other work treating the dominant heavy-ion species of magnetospheric origin, O and S ions (Schultz et al., 2017, 2019; Gharibnejad et al., 2019) the classical trajectory Monte Carlo method is employed to describe the secondary-electron-producing channels (single and double ionization, transfer ionization, and single and double stripping) as well as the other inelastic channels (single and double charge transfer and projectile and target excitation) required to model the energy loss and charge state evolution of the precipitating ions in their passage through the atmospheric gas. Data is described and tabulated both as directly obtained from these calculations and normalized to widely accepted recommended values (Hunter et al., 1990) for channels for which recommendations exist. As in the previous work, the overall accuracy and completeness of the data presented is verified by use of a Monte Carlo ion-transport simulation to obtain the stopping power and ion-fraction populations as a function of impact energy in comparison with accepted values. The addition of the present data to models of secondary-electron production in Jupiter’s atmosphere improves such model’s ability to interpret in situ observations of the precipitating ions’ effect by the spacecraft Juno as well as enhancing the physical reality of models of the coupling of the Jovian magnetosphere, ionosphere, and atmosphere.

Application of thermographic testing for the characterization of impact damage during and after impact load

Low-velocity impact damages were monitored in-situ using an infrared camera before, during and after impact load. Thermal images were recorded as a function of time at the front side (impact) as well as at the rear side of the plates using a high frame rate. In CFRP and GFRP specimens with different thicknesses and made of various types of fibers and matrix materials, different kind of damages were observed. The sizes of the heated areas being related to the damages and the amount of energy dissipated into heat was determined quantitatively as a function of impact energy and are a measure of the resistance of the different materials against impact load.

Enhancement of performance of three-dimensional fiber metal laminates under low velocity impact – A coupled numerical and experimental investigation

The main objective of the present study is to examine the level of enhancement in performance of three-dimensional fiber metal laminates (3DFML) under low velocity impact, when reinforced by different types of reinforcing face-sheets (i.e. fiberglass or carbon). Three layup configurations of the fabrics are considered in this investigation. The impact response of each of these configurations is assessed numerically using ABAQUS/Explicit, a commercially available finite element software. Specifically, each configuration’s impact capacity, deformation, contact time, and energy absorption capacity are evaluated. The numerical results are validated by comparison against experimental results. Moreover, a semi-empirical equation is developed for evaluating the impact capacity of such panels, as a function of impact energy, capable of accounting the influence of any type of reinforcement. Finally, the most efficient reinforced three-dimensional fiber metal laminates are identified based on their impact strength with respect to their overall weight and cost.

Damage of different tungsten carbides under impact-sliding motion

Research on tungsten carbides, used for drag bits inserts in tunnel boring machine, has been going on through decades for the improvement of mechanical and wear properties. The microstructure, the toughness, the hardness as well as the design of inserts are the main parameters in their functionalities and lifetime. This study emphasizes the behavior of tungsten carbide inserts in impact-sliding conditions. In order to test materials under an impact-sliding motion, a test rig has been developed, with a ball on flat configuration. The ball undergoes a vertical sinusoidal motion derived by an electromagnetic shaker. A piezoelectric force sensor and a laser displacement sensor permit the monitoring of the impact energy. Two vertical foils initiate the sliding when the ball impacts the sample, with a given angle. The impact angle variation dampens or accentuates the impact effect over the sliding component. Three types of tungsten carbides with different chemical compositions, production processes and mechanical properties have been tested: a tungsten carbide used nowadays in tunnel boring machine as inserts in drag bits, and two tungsten carbides under development. Two types of ball materials are considered: steel and silicon carbide. Main damages observed in wear scars are abrasive and adhesive wear combined with fatigue cracking. Damage mechanisms are quantified as a function of impact energy, impact angle, number of cycles and counterbody material, with a view to comparing the different tungsten carbides. Wear volume results show that inserts material currently used in the industry has a wear factor ten times higher than the two others, but is less prone to cracking. A numerical simulation with ABAQUS Explicit gives an insight of the wear process. Compressive and tensile stresses at the contact explain the cracks formation at the top of the wear scar. Tensile stresses may promote cracks formation and their propagation.

Single electron transfer in He+-He+ collision and production of helium atom

The four body Born distorted wave (BDW-4B) approximation with correct boundary condition is used for single electron transfer in He+-He+ collision. The post and prior total cross sections are obtained in the energy range 10–1000 keV/amu and the post-prior discrepancy is estimated. The sensitivity of the results with respect to the choice of the final helium-like ground state wave function is evaluated through two different wave functions. The importance of the dynamic electron correlations is tested as a function of impact energy. Additional experimental data at higher impact energies is needed for a better assessment of the validity of the present theory.

Influence of Stacking Sequence on the Impact and Postimpact Bending Behavior of Hybrid Sandwich Composites

A new hybrid sandwich structure was developed by using carbon, e-glass, and s-glass fabrics as reinforcement materials, an epoxy resin as the matrix material for face sheets, and a PVC foam as the core material. Six different configurations were prepared. Sandwich composites plates with different stacking sequences were subjected to low-speed impacts will energies of 7.5, 15, and 22.5 J. Their impact response is analyzed and reported in terms of the peak load as a function of impact energy. After impact tests, 3-point bending tests were conducted to determine the bending behavior of the sandwich composites after impacts in terms of their flexural strength. The results obtained showed that the use of carbon fabrics in the face sheets increased the peak loads for all the impact energies considered. The presence of carbon fibers in skin regions increased the flexural strength of the composites, but e-glass fibers decreased this strength.

Single-electron exchange in H–H and He+–H collisions

The prior version of the four-body Born distorted wave (BDW-4B) approximation is formulated and used to study single-electron capture in H–H and He+–H collisions. The total cross sections are obtained in terms of six-dimensional numerical quadratures at intermediate and high impact energies. The role of dynamic dielectronic correlation is investigated as a function of impact energy. The results of the total cross sections for the post version of the BDW-4B method are also reported and the post–prior discrepancy is estimated. Comparisons of the present results with the available experimental data are made and good agreement is obtained.

Coupling of collective excitation in proton and photon interaction with PAHs

SynopsisCollective excitation in polycyclic aromatic hydrocarbon molecule is studied in collision experiments with intermediate velocity (50-180 keV) proton and FUV (15-40 eV) photon energy. In proton impact experiments a clear comparison between pure ionization and capture ionization (or pure capture) process is done on the basis of ionization, evaporation, fragmentation process as a function of impact energy. Two mechanisms: large impact parameter collective excitation mode and closer encounters with higher amount of electronic energy loss leading to fragmentation were observed in proton collision process. The photon impact results were used to understand the origin of evaporation processes.

X-Ray Refraction Techniques for Fast, High-Resolution Microstructure Characterization and Non-Destructive Testing of Lightweight Composites

X-ray refraction is based on optical deflection of X-rays, similar to the well-known small angle X-ray scattering, but hundreds of times more intense, thus enabling shorter measurement time. We show that X-ray refraction techniques are suitable for the detection of pores, cracks, and in general defects. Indeed, the deflected X-ray intensity is directly proportional to the internal specific surface (i.e., surface per unit volume) of the objects. Although single defects cannot be imaged, the presence of populations of those defects can be detected even if the defects have sizes in the nanometer range.We present several applications of X-ray refraction techniques to composite materials:- To visualize macro and microcracks in Ti-SiC metal matrix composites (MMC);- To correlate fatigue damage (fibre de-bonding) of carbon fibre reinforced plastics (CFRP) to X-ray refraction intensity;- To quantify the impact damage by spatially resolved single fibre de-bonding fraction as a function of impact energy in CFRP laminates.An example of classic high-resolution computer tomography of an impact-damaged CFRP will also be presented, as a benchmark to the present state-of-the-art imaging capabilities. It will be shown that while (absorption) tomography can well visualize and quantify delamination, X-ray refraction techniques directly yield (spatially resolved) quantitative information about fibre de-bonding, inaccessible to absorption tomography.

Evaluation of a critical impact energy in GFRP under fatigue loading

Abstract Defects in fibre reinforced polymer structures, such as impact damages, have a major influence on the fatigue behaviour. Impacts may occur during the lifetime of composite structures and lead to delaminations between adjacent layers with different fibre orientations and to matrix cracks within the layers. Specimens made of a glass fibre non crimp fabric were produced by vacuum assisted resin transfer moulding. Low velocity impact damage was introduced by use of a drop weight with a hemispherical head. The specimens were tested under fatigue loading with a stress ratio of R = −1 (tension–compression). The aim was to characterise damage development in fatigue testing of fibre reinforced polymers as a function of impact energy, lifetime and stress level. Therefore, the stiffness degradation during fatigue testing due to matrix cracks, delaminations, fibre failure and temperature development of the specimens was plotted vs. the number of load cycles. In interrupted fatigue tests with defined numbers of load cycles the influence of impact damages on matrix crack development was determined and correlated with stiffness degradation. Furthermore, thermoelastic stress analysis was performed during the interrupted tests in order to determine stress concentrations in the area of impact damage.

Experiments on shock-absorbing capacity of granular matter under impact load

Granular matter is a complex energy dissipation system. The friction and the viscous contacts among particles can dissipate effectively the system energy caused by external impact load. The force chain structure in granular system can extend the local impact in spatial dimension and expand the instantaneous impact in temporal dimension, thus to obtain the effective shock-absorbing effect. To investigate the absorbing capacity of granular matter under an impact load, in the present study, we develop an experimental system, in which a rock ball impacts granular matter in a cylinder under gravity, and the impact force on the cylinder bottom is measured with three load cells. The influences of particle size, material propery, thickness of granular matter on shock-absorbing capacity are discussed. The results show that irregular particles have more shock absorbing capacity, while the large-size particles have a slightly higher shock absorbing capability than the small-size particles. The thickness of granular matter, H, is a key parameter to affect the shock-absorbing. Critical thickness, Hc, is obtained in the experiments. The shock-absorbing capacity of granular matter is enhanced with H increasing when HHc, while H has little influence on shock-absorbing when H>Hc. The resutls above are obtained with constant impact energy. Critical thickness Hc should be a function of impact energy and will be determined in the next study. With the experiments on shock-absorbing capacity of granular matter, it can reveal basic mechanical behaviors of granular materials and be applied in mechanical vibration absorptions.

Analysis of the effect of impact damage on the strength characteristics of a composite

Theoretical and experimental investigations into the loss of the static tensile strength of a KMKU-2M.120. E01 composite after low-speed impacts of different energy have been carried out. All calculations are performed by the method of finite elements. The drop in the strength as a function of impact energy is estimated according to two criteria: the criterion of an equivalent hole (the upper limit of loss of strength) and the criterion of concentration (the lower limit of loss of strength). The results obtained agree closely with experimental data and therefore can be recognized as reliable.