High Velocity Impact Research Articles

Acceleration of metal plates by hybridization of electrical and chemical energy for potential application in high-velocity impact welding

Vaporizing foil actuator welding is employed to connect dissimilar metals by utilizing the energy of an electrical explosion as the driving force for flyer plate acceleration. Herein, the electrical and chemical energies of explosives were combined to increase flyer plate velocity. A metal foil or wire mesh was used as an actuator, and a small amount of explosives was placed on the foil. Uniform acceleration of the flyer plate on the actuator was recorded using a high-speed video camera. The electrical energy applied to the actuator was measured synchronously by filming. The explosion of chemical explosives was successfully initiated owing to the electrical explosion of the actuator. In all experiments, the combination of the electrical explosion and chemical reaction improved the acceleration of the samples, facilitating higher velocities. The impact of the actuator type (mesh or foil) and the electric discharge parameters on the performance was studied. While foil actuators were more efficient in experiments on electric explosions alone, mesh actuators were superior when the chemical explosive was added. Explosions of the mesh actuator could initiate low density pentaerythritol tetranitrate (PETN) (the space-filling rate of PETN was approximately 30%). An explosive force of 0.3 g of PETN was converted into a driving force, imparting the flying plate with a velocity greater than 210 m/s. Electrical energy consumption for PETN initiation may be assumed to have an insignificant impact on flyer plate acceleration. In future, the proposed method may be used to connect heavier and thicker materials without expensive high-performance capacitors.

A review of armour's use of composite materials

Composites with a laminated structure come from stacking ceramic and metal in a particular order. Because of their high strength and hardness, low density of ceramics, and extraordinary flexibility, metals can be used as bulletproof armour. The bullet anti-penetration system includes a ceramic screen that slows down the projectile and splits it up and a metal backplate that plastically deforms to absorb the projectile's kinetic energy. Laminates have several downsides, including weak interface bonding, a tendency for tip cracks due to increased internal stress, and a jarring difference between the metal and ceramic properties. Crack migration and propagation can cause abrupt changes in material characteristics at the ceramic–metal contact. A drop between the ceramic panel and metal backplate can be easily triggered when a ceramic panel is impacted, as cracks form in the interlayer. In this area, the interface bonding strength is still inadequate. In this review, we looked at the meshless smoothed-particle hydrodynamic method for high-velocity impact and massive deformation, the finite-element simulations of interface impact resistance and the first-principles predictions of interface strength. The paper concludes with numerous suggestions for future improvement: Further study is required on ceramic toughening to increase the compatibility of ceramic panels and metal backplates, the performance transition between ceramic and metal, and the reliability of ceramic–metal laminated materials. It is critical to study ways to strengthen metals. More multiscale research using methods like the phase-field method, finite element analysis, and first-principles computations, focusing on how to mix these techniques naturally and successfully, is needed to reinforce metals by introducing nano-phases into metal matrix composites while still retaining the metal's ductility. The latest study that emphasises the potential advantages of hybrid materials, specifically the combination of aramid and kenaf fibres, highlights a notable progression in the domain of armour technology.

The transformation between different modes of motion of particles in steady aeolian transport

Aeolian sediment transport is an important morphodynamic process that drives geomorphological evolution, affects the climate system, and induces various natural disasters. The creep load involves both particles of a sufficiently large size that cannot be easily lifted to the upper air, as well as smaller particles that can transition between different modes of motion, although the contribution of the latter has rarely been investigated. In this study, we investigate the features of the saltation cycle, namely the time period from the moment a particle is entrained into the air to when the particle is again trapped in the bed, and the transformation mechanism between creep, reptation, and saltation by directly simulating the steady-state sand transport of particles within the saltation regime. The results indicate that a saltation cycle generally contains one to tens of individual hop processes, with the mean and standard deviation of the hop times decreasing with the increasing friction velocity, owing to the presence of more energetic particles at the bed surface. Over half of the transported particles move in creep or reptation model because a moving particle generally experiences frequent transition between creep, reptation, and saltation. Furthermore, the fundamental reason for the change in the mode of motion is the strong impact velocity dependence of the total coefficient of restitution during the rebound process. Current rebound models predict a reasonable coefficient of restitution only if the particle impacts the bed at a moderate velocity; however, their predictions deviate from the actual situation at relatively low or high impact velocities. These findings enhance our understanding of the motion dynamics of particles within wind-blown sand movements, and further reduce the uncertainty in predicting their mass flux in different modes of motion.

Numerical and experimental investigation of impact strength and fracture mechanism of Kevlar and Hemp elastomeric thin biocomposite laminate under high-velocity impact: A comparative study

Thin composite structures reinforced with woven fabrics are widely used in many industrial sectors due to their lightweight, easy access, and high specific performance. Due to safety, the study of fracture mechanisms and energy absorption of thin composite structures is significant. In this study, Kevlar and Hemp elastomeric thin biocomposite laminates with an elastomeric matrix filled with natural lignin filler with a low carbon footprint and with the aim of the sustainability concept of environmental protection have been designed experimentally and numerically for testing under high-velocity impact. The impact resistance of elastomeric composites reinforced with natural fillers is less reported. Good interaction of lignin-filled elastomeric matrix with woven hemp fabric is expected to show impact performance comparable to Kevlar-reinforced composites. For this purpose, Kevlar and hemp thin elastomeric biocomposites are tested under high-velocity impact with almost the same surface density. Also, tensile and dynamic compression tests (Hopkinson test) were performed to check the mechanical properties of the elastomer layer. The proposed laminates' penetration resistance and fracture behavior during an impact according to the Kevlar and hemp fabric constituent material model and the user-defined material model (VUMAT) for the nonlinear behavior of elastomeric materials considering the damage criterion in ABAQUS/Explicit confirmed. The results show, In the thin elastomeric hemp biocomposites, the tensile failure and stress transfer to the surrounding bundles cause more yarns to participate in the load-carrying process. As a result, the low penetration depth and more significant protection margin in fully green hemp composites provide impact performance comparable to Kevlar elastomeric composites.

Study of the in-plane crashworthiness performance of 6-legged starfish-inspired structures

Bio-inspired design is an impressive design method that improves a structure's crashworthiness performance and mechanical features. A cellular structure bio-inspired by a 6-legged starfish shape has been developed. Accordingly, this study examines the in-plane crushing behavior and crashworthiness of the 6-legged starfish-inspired structure (6LSIS). Analytical solutions were built based on the principle of energy balance to estimate the plateau stress in low-impact velocity conditions. Plateau stresses are related to high-impact velocities using a curve fitting method for a given wall's thickness. The predictions matched the numerical results. The crashworthiness performance of the 6LSISs mainly depends on wall thickness, impact velocity, and loading direction. It has been observed that an increase in wall thickness and impact velocity results in an enhancement in plateau stress ( σpl), specific energy absorption (SEA), and peak load (PL) in both directions. However, if the wall thickness is >0.3 mm, SEA decreases due to an increase in the structure's mass. The in-plane crushing direction ( X or Y) determines the crushing strength and deformation mode of the structure. This study illustrates that the crashworthiness of the structure in the X-direction is superior to that in the Y-direction.

Numerical modelling of high velocity impact problem involving non-linear viscosity

The paper is aimed at developing numerical models for simulation of hypervelocity collisions of small fragments with honeycomb shields relevant to Space structures protection from impact of debris fragments. Numerical modelling of hypervelocity collision within hydrodynamic approach reveals effects that are inconsistent with physical sense. In order to overcome these inconsistencies and to achieve justified description of the process of penetration and fracturing numerical model was developed assuming the impactor and projectile being viscous materials. Despite constant viscosity we investigate two phenomenological relationships for viscosity: depending on temperature and depending on deformation rate. The exponential dependence of viscosity on material state (temperature and second invariant of strain rate deviator) makes the material manifest both properties of fluid and solid state of matter. Taking into account viscosity allows to suppress jets at symmetry axis and small-scaled ejecta. The usage of non-constant viscosity results in a more physically based scenarios for fracturing of the shell obtained in numerical simulations.

Graphene oxide coated silicon carbide films under projectile impacts

The quest for hybrid materials to withstand extreme loading conditions has been a canonical field of research over the past decades. As an emerging hybrid material, graphene oxide (GO)-silicon carbide (SiC) offers remarkable thermo-chemo-mechanical properties with applications in defense, energy, and aerospace engineering. Researches to unravel the various properties of the aforementioned material subjected to different loading conditions have been on the rise to further promote its potential for the pertinent industries. Nonetheless, impact resistance characterization of such composite received less attention due to experimental and computational difficulties. Here, the aforementioned problem is investigated by leveraging ReaxFF molecular dynamics simulations. Accordingly, the response of 4H-SiC thin films coated by GO samples under indentation and high-velocity projectile impact is assessed. It is found that (a) composite films containing GO samples with higher oxidation degree demonstrate softer behavior under indentation, and (b) fracture pattern and penetration-resistance under high-velocity impact are contingent on the oxidation degree of the coating layers. In essence, impact-induced complete perforation is more localized to the impacted zone as oxidation degree of the coating layers increases. Therefore, oxidation content can be considered as a novel tuning factor for the fracture behavior of the GO-SiC thin films under projectile impacts. The influence of oxygen functional groups on the interaction energy between GO and SiC layers are also discussed. The findings of this study reveal some insights into the bottom-up design pathways for developing novel protective barriers in which GO is used as a coating layer or reinforcement for SiC ceramics.

Ballistic performance and damage behavior of three-dimensional angle-interlock woven composites under high velocity impact: Experimental and numerical studies

Three-dimensional angle-interlock woven composites (3DAWCs) are usually employed as exposed components in aerospace and other high-tech areas due to their superior impact resistance. In this work, the experimental characterization and numerical modeling are combined together to study the ballistic performance and damage behavior of 3DAWCs under high velocity impact (HVI). The initial-residual velocity relation is examined by ballistic impact test and the penetration process is recorded by high-speed camera. A nonlinear finite element (FE) model based on a multi-scale modeling framework is established to simulate the ballistic impact response and damage behavior of 3DAWCs. The proposed FE model is verified by comparing the predicted initial-residual velocity curve and penetration propagation with the experimental data. Parameter analysis is conducted to address the influences of projectile diameter and impact angle on the impact performance of 3DAWCs and the corresponding damage mechanisms are revealed in detail. The present work provides a transferable approach for studying the HVI problems of other textile composite structures.

High-velocity impact damage and compression after impact behavior of carbon fiber composite laminates: Experimental study

In this paper, the impact resistance of carbon fiber/resin composite laminates with a thickness of 2.5 mm at different impact velocities, angles and positions was investigated experimentally. In the process of high-velocity impact, fiber shear failure and tension failure are the main failure modes. When the impact velocity is 300 m/s, the fiber tension failure and matrix compression failure under oblique impact are more than that under normal impact, and the energy absorption of laminates is also lager than that under normal impact. The ballistic limits, energy absorption and delamination area of the center and edge impact of laminate are similar. In addition, the CAI tests are conducted to study the influence of different positions on the residual compressive strength of laminates after high-velocity impact, and the fracture loads and failure modes of two impact positions are quite different. The failure modes of the center impact laminate are main buckling failure, and the failure modes of the edge impact laminate are compression failure near the bullet hole side of the fixture and buckling failure near the center of the laminate. The research results can provide a reference for the residual strength of laminates after impact at different locations in practical situations.

Bio-inspired interleaved hybrids: Novel solutions for improving the high-velocity impact response of carbon fibre-reinforced polymers (CFRP)

We propose a novel design methodology consisting of bio-inspired (BI) and interleaved layups to develop hybrid carbon fibre-reinforced polymer (CFRP) composite structures for improved high-velocity impact (HVI) performance. Firstly, we apply a BI helicoidal design method consisting of various pitch angles (considering both thick- and thin-ply CFRP) to develop BI monolithic CFRP laminates. Secondly, we apply the interleaving design method to develop BI hybrid CFRP-based laminates interleaved with blocks of BI Zylon fibre-reinforced polymers through the thickness. We evaluate their response and compare it with traditional quasi-isotropic (QI) hybrid bulk layups. In addition to hybridising with Zylon, we apply titanium (Ti) foils to both the monolithic and hybrid CFRP-based laminates to investigate and compare their response. For all our hybrids, we kept the ratio of the hybridising material(s) to be less than 50% to ensure suitable in-plane mechanical properties and aimed at a target areal weight of 0.95 g/cm2. We also manufactured QI thick- and thin-ply monolithic CFRP laminates as baselines. We tested all laminates at 170 and 210 m/s and studied their response and failure modes. Our results show that the average energy dissipation of the QI monolithic thin-ply baseline improved by up to 22% by changing the layup from QI to BI, and by about 118% by changing the baseline QI layup to BI hybrid interleaved. Post-mortem analysis reveals that there are additional failure mechanisms activated in the BI hybrid interleaved layup with respect to the baseline.

Optimization of Johnson-Cook Constitutive Model Parameters Using the Nesterov Gradient-Descent Method.

Numerical simulation of impact and shock-wave interactions of deformable solids is an urgent problem. The key to the adequacy and accuracy of simulation is the material model that links the yield strength with accumulated plastic strain, strain rate, and temperature. A material model often used in engineering applications is the empirical Johnson-Cook (JC) model. However, an increase in the impact velocity complicates the choice of the model constants to reach agreement between numerical and experimental data. This paper presents a method for the selection of the JC model constants using an optimization algorithm based on the Nesterov gradient-descent method. A solution quality function is proposed to estimate the deviation of calculations from experimental data and to determine the optimum JC model parameters. Numerical calculations of the Taylor rod-on-anvil impact test were performed for cylindrical copper specimens. The numerical simulation performed with the optimized JC model parameters was in good agreement with the experimental data received by the authors of this paper and with the literature data. The accuracy of simulation depends on the experimental data used. For all considered experiments, the calculation accuracy (solution quality) increased by 10%. This method, developed for selecting optimized material model constants, may be useful for other models, regardless of the numerical code used for high-velocity impact simulations.

Pseudo-Spectral MPSP-Based Unified Midcourse and Terminal Guidance for Reentry Targets

A unified optimal guidance scheme is presented in this paper for both midcourse and terminal phases combined. It minimizes the total deceleration resulting in enhanced range and/or higher impact velocity, while satisfying the terminal constraints on impact angle and miss distance. State-dependent terms are included in the cost function of the recently-proposed Generalized QS-MPSP and, because of its similarity with the Pseudo-Spectral philosophy, it is renamed as ‘Pseudo-Spectral MPSP’. Extensive simulation studies with different engagement scenarios illustrate the effectiveness of the proposed guidance to engage with incoming high-speed ballistic targets.

Estimation of non-linear mechanical properties of rubber using Split Hopkinson pressure bar

The material non-linearity is a very important phenomenon in the behavior of the materials subjected to high strain rate loading. Rubber is a material which has high damping properties due to which it is more vulnerable in applications that involve absorption of vibration and shock; generally, these damping materials are subjected to high strain rate loading while absorbing the load. In the present work, various types of rubbers are subjected to very high-velocity impact due to which a very high strain rate loading is applied on the rubber specimens through the usage of Split Hopkinson Pressure Bar apparatus. The behavior of the rubber specimens at this high-velocity impact loading is studied through the variation of stress, strains, and strain rate with time. A comparison is drawn between various rubbers and the best rubber for the impact applied, is evolved and the same is presented in the work.

Ballistic Performance of Thermally Exposed CFRP Composites

In this investigation, high velocity impact test was carried out to study the after effect of thermal loading on ballistic limits of composite laminates. Plain woven carbon/epoxy laminates with nominal thickness of 2.3 mm were fabricated by compression moulding technique. To study the effect of thermal loading, laminates were exposed to different temperatures of 60°C, 80°C, 100°C, 120°C, 140°C and 160°C for 24 h in hot air oven and brought back to room temperature. Impact test was carried out using single stage gas gun for velocity up to 115 m/s. The bullet used was Æ 9.6 mm and mass 14.20 gm. The results show that ballistic limit reduces from 83 m/s to 62 m/s with increase in loading temperature from 30°C to 160°C. For impact velocity above ballistic limit, energy absorbed by the laminates reduces with increase in loading temperature. Shear plug formation was observed during experiment as reported in literatures [4, 5 and 6]. An energy base mathematical model is employed to predict the ballistic limit. The model considered the energy loss due to various failure mechanisms that occurred during impact test. The predicted ballistic velocity and energy absorbed by laminates show good agreement with the experimental results.

Study on dynamic properties of lightweight ultra-high performance concrete (L-UHPC)

Ultra-high performance concrete (UHPC) is being considered as a potential material for concrete structures subject to impact and blast loads due to its exceptional strength and ductility characteristics. In this study, a lightweight ultra-high performance concrete (L-UHPC) was developed using fine lightweight aggregate. To further understand the mechanical response of L-UHPC at high impact velocities, the dynamic properties (such as failure pattern, peak stress, DIF, stress–strain curve, and toughness) of L-UHPC were investigated and the effect of steel fiber type on dynamic properties was analyzed. According to the research findings, the L-UHPC exhibits significant sensitivity to variation of strain rate, it experiences more damage, exhibits a higher peak stress, and absorbs more energy when subjected to a higher strain rate. The steel fiber shape exhibited little effect on both quasi-static and dynamic properties. Furthermore, an empirical formulate of dynamic increase factor (DIF) for L-UHPC with different steel fiber was proposed. At last, the failure mechanism of L-UHPC was analyzed. The experimental findings can provide a valuable reference for the further understanding and studying the dynamic characteristic of concrete with ultra-high strength and low density.

Contribution of energy dissipation to dynamic fracture resistance of the turtle carapace

The turtle carapace is a biological armor possessing superior damage tolerance. In spite of efforts to characterize the mechanical properties of such biological armor, the protection mechanisms associated with the multilayered structure of turtle carapace are largely unknown. In this study, we carry out the calculations of energy dissipation in dynamic fracture of the turtle carapace. The plastic deformation of keratin-collagen bi-layer, keratin-collagen interfacial debonding, collagen-bone interfacial debonding and crack growth in the boney layer are accounted for in the analyses. It is found that the interfacial debonding and plastic deformation of the keratin-collagen bi-layer contribute equally to toughening of the carapace at low impact velocity, while plastic energy dissipation dominates in the case of high impact velocity. As the impact velocity is increased, energy dissipation in the turtle carapace decreases at first and then increases. We reveal that the low energy dissipation of carapace at intermediate level of impact velocity is attributed to small plastic zones in the keratin-collagen bi-layer. Furthermore, we have identified the role of the waviness of the keratin-collagen and collagen-bone interfaces. The presence of wavy interfaces enhances plastic energy dissipation of the keratin-collagen bi-layer and promotes interfacial debonding, thereby suppressing crack propagation in the boney layer. The findings provide mechanistic explanations for incorporation of wavy interfaces in the multilayered structure of turtle carapace.

Dynamic impact and tensile strength characteristics of novel shear thickening fluid (STF)-treated fabric and modeling tensile strength using artificial intelligence

A series of shear thickening fluids (STFs) were prepared based on dispersed fumed silica in virgin polyethylene glycol (V/PEG) and modified PEGs by malonic acid (M/PEG) and tartaric acid (T/PEG). Rheological examination revealed that modification of PEG to a higher chain length of medium molecules remarkably improves STF peak viscosity and decreases the critical shear rate. High-velocity impact resistance of V/STF, M/STF, and T/STF-treated fabric was investigated at different layers and impact velocities and found significant improvement over neat fabric targets. Investigation of the results of two-layer samples showed the energy dissipation of V/STF, M/STF, and T/STF-treated fabrics at an impact velocity of 240 m/s is improved by 30.04%, 40.60%, and 46.06%, compared to the neat fabric, respectively. Furthermore, the tensile strength test revealed that these STFs fill the spaces between the fibers and make the fabric stronger and more resistant to breaking. In addition, a Linear/Nonlinear artificial intelligence regression analysis was performed. The results showed a strong correlation between composite mechanical response and speed. The proposed model can be further used to predict material behavior at other tensile speeds.

Numerical study on the effects of oblique impact on the ballistic behavior of 3D angle interlock woven fabric

3D angle interlock woven fabric(3DAWF) has great potential for impact protection. This paper investigates the ballistic mechanism of 3DAWF(5 layers of angle interlock – through the thickness) under normal and oblique impact. The full-size mesoscale model of 3DAWF under different impact directions and angles was established and systematically studied to reveal the 3DAWFs’ ballistic mechanism. The numerical studies of 3DAWF subjected to 0°, 15°, 30°, 45°, and 60° oblique impacts from two impact directions along 3DAWF structure configurations were carried out. We found that 3DAWFs’ ballistic performance increases non-linearly with impact obliquity. The ballistic mechanisms change with impact directions because of 3DAWFs’ anisotropic structure. This work also demonstrates the impact damage mechanism, energy absorption evolution, and stress wave distribution of the 3DAWF under oblique high-velocity impact. The findings are constructive for the 3DAWF applicated in ballistic protection.

Novel zone-based hybrid laminate structures for high-velocity impact (HVI) in carbon fibre-reinforced polymer (CFRP) composites

We propose novel zone-based hybrid laminate concepts for improving the high-velocity impact (HVI) response of baseline carbon fibre-reinforced polymer (CFRP) composites while maintaining similar areal weights and retaining substantial in-plane mechanical properties by requiring that about 80% (by mass) of the baseline CFRP is kept in the hybrid concepts. We identify three zones along the thickness of the laminate according to their role during HVI and implemented tailored materials in these zones to improve the HVI response. We studied a wide range of materials, including: fibre reinforcements of carbon (thin- and thick-plies), glass, Zylon and ultra-high molecular weight polyethylene (UHMWPE); a shape memory alloy/carbon fabric; and ceramic, alumina and titanium sheets. All laminate concepts have similar areal weights for a meaningful comparison. After defining the various concepts, we manufactured and measured their specific dissipated energy under HVI, and finally carried out post-mortem analysis (including C-scan and microscopy). The results show up to 95% improvement in energy dissipation over the baseline quasi-isotropic (QI) CFRP configuration.

Alcohol-induced elevation in the dynamic Leidenfrost point temperature for water droplet impact

In the present study, an experimental investigation is conducted to explore the alcohol additive effect on water droplet impact on a smooth red copper surface and to construct impact regime maps. The observations show that the alcohol additives can effectively facilitate droplet atomization and breakup, and increase the dynamic Leidenfrost point temperature. An interesting phenomenon is noted that the dynamic Leidenfrost point temperatures of alcohol-added water droplets at lower impact velocities are obviously elevated compared with pure water at higher impact velocities. In other words, the addition of a small amount of alcohol additive can effectively compensate for the decrease in the dynamic Leidenfrost point temperature caused by smaller impact momentum. A new triggering mechanism of the dynamic Leidenfrost effect is proposed with the surface roughness effect taken into consideration. An approximation model based on the pressure balance criterion is then developed to discuss the underlying physics of the alcohol-induced elevation in the dynamic Leidenfrost point temperature. Combining the scaling analysis of vapor layer thickness, a scaling relation of the dynamic Leidenfrost point temperature is derived, and the predictions agree well with present and previous data. It is concluded that the present findings provide an effective method to expedite the transformation from film boiling to transition boiling for heat transfer improvement with an increased dynamic Leidenfrost point temperature, simply by adopting alcohol additives to regulate the droplet thermophysical properties.