High Velocity Impact Research Articles

High-Velocity Impact Damage Assessment of Aluminum-Honeycomb-Cored Banana-Fiber-Reinforced Composite Structures Under Elevated Temperatures

High-Velocity Impact Damage Assessment of Aluminum-Honeycomb-Cored Banana-Fiber-Reinforced Composite Structures Under Elevated Temperatures

Research on damage repair and high-velocity impact characteristics of thermoplastic composites

Low-velocity impact (LVI) can result in imperceptible damage to carbon fiber reinforced thermoplastic composites (CFRTP) laminates during service, leading to a reduction in structural strength. The thermal repair of damaged CFRTP laminates is conducted using the repairability of thermoplastic resin at high temperatures. However, the high-velocity impact characteristics of CFRTP laminates following thermal repair remain uncertain. This study examines CFRTP laminates made of two different materials (CF/PEEK and CF/PPS) with varying levels of low-velocity impact damage, and investigates the thermal repair process. A comparative experimental analysis examined the high-speed impact characteristics of CFRTP laminates under varying conditions. The results indicate that CF/PEEK laminates consistently exhibit superior compressive properties and impact resistance compared to CF/PPS laminates under similar conditions. Following damage from low-velocity impact, the compressive properties and high-velocity impact resistance of CFRTP laminates decrease, with CF/PPS laminates typically showing a lower performance retention rate. However, the thermal repair process proposed in this study significantly enhances the performance of CF/PPS laminates. Moreover, the degree of performance healing in CF/PPS laminates is consistently higher than that in CF/PEEK laminates, which is closely related to the semi-crystalline nature of PEEK resin.

On-the-fly clustering for exascale molecular dynamics simulations

Computational resources have experienced exponential growth in the last decades enabling the simulation of complex physical problems at the cost of a massive increase in data storage. This is especially true for N-body simulations now reaching billions or trillions particles in certain cases. To overcome the drawbacks of data storage on disk for post-processing purposes, on-the-fly analysis has gained momentum but still represents a challenge in both its implementation and efficiency without impacting the simulation engine performances. This work provides a new in-situ procedure for features detection in massive N-body simulations, leveraging state-of-the-art techniques from various fields. Based on a discrete-to-continuum paradigm shift, particles and their respective physical quantities are projected onto a 3D regular grid before applying image analysis algorithms to group voxels based on specific user-defined criteria. A significant extension to the hybrid parallelism of connected component analysis within the image processing community is also introduced in the present study. Traditionally operating in shared memory parallelism, this extension now incorporates both distributed and shared memory approaches. The implementation is carried out within the exaStamp classical Molecular Dynamics code, a variant of the open-source exaNBody platform (see section 6). This adaptation allows for the on-the-fly analysis of multi-billion atoms samples with at most a 1.3% overhead. In addition, the entire framework is benchmarked up to 32768 cores. The applicability of the present approach is demonstrated on the case of a spall fracture in a tantalum sample as well as high velocity impact of a tin droplets on a rigid surface.

High-Velocity Impact Response of Directly Recycled Aluminium Alloy AA6061 Plates

High-Velocity Impact Response of Directly Recycled Aluminium Alloy AA6061 Plates

The rebound law of micro-particle on amorphous alloys under high impact velocities

Compared to their crystalline counterparts, amorphous alloys due to disordered structures are expected to have higher elasticity of deformation. However, in this work, we use the micro-ballistic impact technique to show a smaller dynamic redound of micro-particles on a Zr-based amorphous alloy than that on its corresponding polycrystalline target. We find that the two alloys follow the same rebound law of micro-particle under low impact velocities, but with increasing impact velocity the amorphous alloy exhibits a faster decrease in rebound velocity of micro-particle. This lower rebound results from the easier activations of shear banding in glassy structures, thus contributing to more significant energy dissipation during the micro-particle impact. Further analyses imply that the amorphous alloys and their crystalline counterparts are more favorable in shock wave and projectile protection, respectively. This work is useful in the understanding of the dynamic elasticity and shock energy dissipation of amorphous alloys under micro-particle impacts.

Effect of High-Velocity Impact Loading on Concrete Slabs Reinforced by Metallic Strips from Soft Drink Cans as Fiber

Effect of High-Velocity Impact Loading on Concrete Slabs Reinforced by Metallic Strips from Soft Drink Cans as Fiber

Structural performance enhancement: bio-inspired honeycomb solutions for high-velocity hail impact challenges

Structural performance enhancement: bio-inspired honeycomb solutions for high-velocity hail impact challenges

High-Velocity Impact Performance of Ballistic Fabric Using Core-Spun Compound Yarns.

In this paper, the usage of core-spun compound yarns in ballistic fabric to improve ballistic performance is considered, as with the use of core-spun compound yarns, the yarn friction inside the fabric is enhanced, and, therefore, the energy absorption capability of the fabric is expected to increase. Three types of fabric were developed and compared. Fa refers to a woven type made with 100% Kevlar® filament yarns. Fb was woven with core-spun compound aramid yarns, which were made of Kevlar® filament yarns spun with staple aramid fiber. Fc was woven with core-spun compound polyester yarns, which were made of Kevlar® filament yarns spun with staple polyester fiber. There were two main purposes for comparing these types. The first was to confirm if the ballistic performance could be improved with the usage of core-spun compound yarns instead of pure filament yarns. The second was to investigate if different compositions of spun fiber would influence ballistic performance. The research results are positive and quite interesting. They show that the usage of core-spun compound yarn could indeed help to increase ballistic performance and that core-spun compound aramid yarns are better than core-spun compound polyester yarns in this function. The research was carried out using both ballistic tests and FEA models.

Experimental investigation of high-velocity impact response and compression after impact behavior of continuous carbon fiber thermoplastic composites

In order to meet the urgent needs for the application of thermoplastic composite structures in aircraft manufacturing and other fields, the impact resistance and damage tolerance of continuous carbon fiber reinforced thermoplastic composite laminates (CCFRTP) are investigated by high-velocity impact (HVI) and compression after impact (CAI) experiments in this paper. The impact experiment results show that the ballistic response of laminates under small-angle conventional impact is similar, and the impact resistance of laminates under large-angle oblique impact is significantly improved. The failure mechanism of laminates under high-velocity impact is revealed by analyzing the impact process of the projectile, the energy absorption level, the failure morphology and internal damage degree of laminates comprehensively. It is clear that the impact angle and velocity of the projectile will significantly affect the coupling form of the failure mechanism and lead to differentiated results. The results of in-plane compression experiment of laminates with impact damage show that the bearing capacity of laminates is significantly weakened by high velocity impact damage, and the residual strength of laminates is directly determined by the mode and degree of impact damage. In particular, through the analysis of the energy absorption mechanism, a trend prediction model of ballistic limit value with impact angle is established, and the influence of high-velocity impact damage on the residual strength of laminates is revealed. This study provides a better understanding of the mechanical response of thermoplastic composite structures to high-velocity impact loads.

Biomimetic Modular Honeycomb with Enhanced Crushing Strength and Flexible Customizability.

The integration of biomimetic principles into the sophisticated design of honeycomb structures has gained significant traction. Inspired by the natural reinforcement mechanisms observed in tree stems, this research introduces localized thickening to the conventional honeycombs, leading to the development of variable-density honeycomb blocks. These blocks are strategically configured to form modular honeycombs. Initially, the methodology for calculating the relative density of the new design is meticulously detailed. Following this, a numerical model based on the plastic limit theorem, verified experimentally, is used to investigate the in-plane deformation models of modular honeycomb under the low- and high-velocity impact and to establish a theoretical framework for compressive strength. The results confirm that the theoretical predictions for crushing strength in the modular honeycomb align closely with numerical findings across both low- and high-velocity impacts. Further investigation into densification strain, energy absorption, and gradient strategy is conducted using both simulation and experimental approaches. The outcomes indicate that the innovative design outperforms conventional honeycombs by significantly enhancing the crushing strength under low-velocity impacts through the judicious arrangement of honeycomb blocks. Additionally, with a negligible difference in densification strains, the modular honeycomb demonstrates superior energy dissipation capabilities compared to its conventional counterparts. At a strain of 0.85, the modular honeycomb's energy absorption capacity improves by 36.68% at 1 m/s and 25.47% at 10 m/s compared to the conventional honeycomb. By meticulously engineering the arrangement of sub-honeycombs, it is possible to develop a modular honeycomb that exhibits a multi-plateau stress response under uniaxial and biaxial compression. These advancements are particularly beneficial to the development of auto crash absorption systems, high-end product transportation packaging, and personalized protective gear.

Dynamic responses of thin-walled FRP-concrete-steel tubular wind turbine tower under horizontal impact loading: Experimental study and FE modelling

Thin-walled FRP-concrete-steel tubular towers (TW-FCSTs), composed of an outer FRP tube, an inner hollow steel tube, and an interlayer of concrete, represent a novel type of wind turbine tower with promising application prospects. Given their potential risks to potential vehicle or vessel collisions, this study investigates the dynamic responses of five cantilevered TW-FCSTs using a horizontal impact device. These TW-FCSTs possess significantly large void ratios (i.e., φ=0.73or0.82) and practical large column sizes (i.e., Dc = 300 mm, Hc = 1500 mm). The experimental programme of this paper investigates several key parameters, including FRP thickness, steel thickness, and void ratio of TW-FCSTs, as well as the velocity and numbers of impact loading. Experimental findings demonstrate the following insights: (1) cantilevered TW-FCSTs exhibit an overall flexural failure mode after the horizontal impact loading; (2) the increase in steel thickness or FRP thickness contributes to greater energy dissipation and reduced localized dent deformation; (3) the higher void ratio results in more pronounced localized dent deformation and less overall deformation in specimens; (4) the proportion of energy dissipation caused by localized dent deformation increased with impact velocity, signifying more severe localized dent deformation at higher impact velocities. The utilization of FE models in LS-DYNA effectively simulates the dynamic performance of cantilevered TW-FCSTs, offering reliable predictions. Parametric studies were conducted to analyze influences of impact mass, impact height, concrete strength, and steel yield strength.

Surface-deformability dependent contact time of bouncing droplets on sessile soap bubbles

HypothesisThe curvature of the free-standing liquid film is expected to modify its surface deformability, thereby affecting droplet bouncing dynamics and possibly tuning the liquid repellency performance in practical applications. ExperimentsIn this study, the bouncing dynamics of water droplets on sessile soap bubbles with different curvatures has been experimentally investigated using high-speed camera. FindsTo resist the impacting droplets, the soap bubbles is observed to show two types of deformation: the geometrical deformation caused by the total impacting force and the pressure distribution induced deformation from the droplet dynamics. The variation trend of the contact time of the droplet with the impact velocity is found to be highly dependent on the surface deformability of the soap bubble. This trend becomes non-monotonic when the soap bubble is large and more deformable. The decreasing contact time with increasing impact velocity can be well captured by a phenomenological model of coupled springs. The increasing contact time for the large soap bubbles at high impact velocities is due to the further compression of the soap bubble by the recoiling droplet, leading to the decoupling of the above two types of bubble deformation.

Research on high-velocity ballistic impact of para-aramid sateen fabric with ZnO nanorods oriented to the development of soft body armor

This study introduces an innovative approach of utilizing ZnO nanorod growing technology to the sateen fabric in order to improve its ballistic performance. Through SEM, FTIR, XRD and XPS analyses, ZnO nanorods with majority length of 1000–1500 nm and fineness of 200–600 nm have been deposited on the surface of sateen fabric surface Compared the fabric with ZnO nanorods (S-11-Nrs) with its neat counterpart, the mechanical properties of S-11-Nrs are increased, especially the inter-filament friction and fabric tensile breaking strength. However, in the impact process, the number of filaments involved in the impact is reduced and the filaments are mainly failure by the shear action of the bullets. Due to these positive and negative effects, the energy absorption of S-11-Nrs displays inferior ballistic energy absorption. Nevertheless, at lower areal density, in the non-perforation test, S-11-Nrs presents less BFS and shows better resistance to the consecutive shotting process compared with the neat fabric. The reason is that the increase of inter-filament friction limits the movement of filaments and thus results in less BFS. In addition, the flexibility, air permeability and moisture permeability are still kept. This research offers valuable insights for the design and development of comfortable soft body armor.

Simulation of shockwave propagation characteristics in nuclear reactor cavity during external steam explosion using unified SPH

Steam explosions in nuclear reactors pose significant risks to reactor safety and containment integrity during severe accidents. This study addresses the challenges of accurately simulating shockwave propagation and structural impact in such events by establishing a unified Smoothed Particle Hydrodynamics (SPH) framework. The proposed SPH model was optimized using GPU parallelization and validated against experimental results from shock tube, underwater explosion and high-velocity impact tests, demonstrating its efficacy in capturing shockwave-structure interactions. The model was applied to simulate steam explosions in the APR1400 reactor cavity under various conditions, examining factors such as the equation of state (EOS) for water, structural materials and explosive forces. The study further found that the choice of EOS and structural material greatly influenced the peak pressure and the extent of damage, with the Mie-Grüneisen EOS producing higher peak pressures and reinforced concrete showing higher damage resistance. These findings suggest that the unified SPH approach provides a comprehensive and robust framework for assessing steam explosion risks, offering crucial insights for optimizing reactor design and safety measures against such events.

Energy absorption characteristics of STF impregnated Kevlar fabric coating GFRP composite structure by projectile high-velocity impact

The new STF impregnated Kevlar fabric coated GFRP (glass fiber reinforced polymer) composite structure obtained by combining STF（shear thickening fluid） impregnated Kevlar fabric and GFRP can obtain strong energy absorption capacity with light weight compared with two separate structures, so it has strong impact resistance. In this paper, the experiments of STF impregnated Kevlar fabric, GFRP laminated plate and STF impregnated Kevlar fabric coating GFRP laminated structure were carried out, respectively. Based on reliable numerical simulation, the macroscopic damage and energy absorption characteristics of the same material in STF impregnated Kevlar fabric, GFRP laminated plate and STF impregnated Kevlar fabric coating GFRP laminated structure were analyzed. The results show that the GFRP laminate and the rear Kevlar fabric in the STF-impregnated Kevlar fabric coating GFRP laminate structure show a larger damage area than that of GFRP laminate and STF impregnated Kevlar fabric alone, and a larger deflection is generated during the process of impact. The increase of the number of layers of Kevlar fabric in the front and back of the laminate and the increase of the thickness of the laminate make the Kevlar fabric absorb more energy. If the energy absorption capacity of GFRP laminates is increased, the number of layers of the front Kevlar fabric can be reduced, the thickness of the laminates can be increased, and materials with greater strength can be added to the front ply of the laminates. However, increasing the thickness of GFRP laminates will reduce the lightweight requirements of laminated structures.

Anomalous size effect of impact resistance in carbon nanotube film

Dynamic mechanical behavior and size-related impact resistance of CNT films are studied by employing laser-induced projectile impact test (LIPIT) and coarse-grained molecular dynamics (CGMD) simulation. The energy dissipation mechanisms of the CNT films are investigated via CGMD simulations. An evident anomalous thickness-dependent effect is directly observed in the experiment, consistent with simulation phenomena. The mechanisms underlying this anomalous thickness-dependent effect are investigated at the atomic scale. The disparities between experiments and simulations are discussed. Our analysis of energy dissipation modes, deformation behaviors during impact, and impact area reveals that kinetic energy change predominantly governs the deformation mode. Meanwhile, a plugging failure mode near the exit face of CNT film is identified at high impact velocity (∼160 m/s), leading to a deterioration in impact resistance and a corresponding reduction in SEA with increasing CNT film thickness. These findings provide a feasible strategy for the protection design of CNT film in broaden protective application scenarios.

Impact response of additively manufactured density-graded open-cell foams

Additive manufacturing has made it possible to fabricate materials that were unachievable with traditional methods. This study focuses on understanding the deformation behavior and energy absorption mechanics of additively manufactured cellular materials with gradually varying densities. Foams have unique deformation behavior due to their intricate topology and composition, resulting in excellent energy dissipation capability. Varying the density can significantly influence their deformation response and improve energy absorption and impact resistance. Voronoi tessellation is employed to model the foams, as it effectively captures the cell morphology in foam structures and produces stochastic cellular topologies accurately. Resin-based additive manufacturing techniques are employed to fabricate cellular materials with varying density configurations for low-velocity and high-velocity impact experiments. The study demonstrates that density-graded foams effectively dissipate a broad spectrum of impact energies, surpassing uniform counterparts by transmitting reduced stress, especially at lower energy levels. This characteristic enhances their suitability for advanced energy absorption applications. The results also show that at high impact velocities, the direction of density gradation influences energy dissipation and peak stress transmission.

A Method of Images to Study Plate-Impact-Induced Cavitation in Aluminum through Molecular Dynamics Simulation

The tensile stress generated by the superposition of two reflection waves in the target plays a critical role in explaining plate-impact-induced spalling. A method of images is proposed to simulate the physical process of wave superposition and this method is applied in order to study the cavitation mechanism in single-crystal Al through molecular dynamics simulation. The critical impact-load velocity for the cavitation obtained by this method is as small as 400 m/s, which is much lower than the result (650 m/s) obtained by the conventional piston-load method. The new cavitation mechanism found is distinctively different from the conventional dislocation-entanglement-induced cavitation under high-velocity impact. The new mechanism involves two key events: firstly, a crack-like defect is formed and its relevant atomic bonds are broken under high tensile stress, resulting in a great momentum of related atoms; and secondly, previous high-momentum atoms collide with the atoms in their running way, resulting in the destruction of the original FCC structure locally and nanovoids or penny-shaped voids being formed. Additionally, the cavitation region, the number of voids, and delamination surfaces increases with the impact-load rate.

Standoff-free vaporizing foil actuator welding: Process principle, experimental validation, and mechanisms analysis

This paper introduces a novel high-velocity impact welding process: the standoff-free vaporizing foil actuator welding (standoff-free VFAW). This technique employs a new type of driving mechanism, overcoming the geometric placement constraints between the flyer plate and the target plate inherent in conventional impact welding processes. It enables welding without requiring an initial standoff distance between the two plates. The feasibility and general applicability of the proposed process were validated through experiments. The welding performance was evaluated using shear tests, peel tests, and microstructural analysis. The results indicate that the proposed process can successfully weld T2 copper to 304 stainless steel and AA5083-H112 to 304 stainless steel. Additionally, this study verified that the proposed process can achieve progressive welding, making it possible to utilize standoff-free VFAW for large-area metal welding. Furthermore, microanalysis revealed the presence of a typical wavy interface characteristic at the joint. Key parameters influencing the welding results were also explored through experiments and finite element modeling, which suggest that the boundary constraints of the workpiece play a key role in the success of standoff-free VFAW. This implies that the initiation of the small and dynamic gap between the flyer and target plates could be the potential mechanism for the proposed process. In summary, standoff-free VFAW presents simplicity and efficiency as its advantages. Moreover, the insights gained from this technique are not limited solely to vaporizing foil actuator welding (VFAW) but could also provide reference points for other high-velocity impact welding techniques.

Dynamic splitting tensile mechanical behavior of magnesia-carbon refractories under impact loading

To enhance understanding of the dynamic tensile failure mechanism of MgO-C refractories, the Split Hopkinson Pressure Bar test combined with digital image correlation techniques were utilized. The dynamic failure behavior of specimens with different heat treatments and graphite content was investigated under various impact velocities. The MgO-C specimens exhibit severer damage and a more tortuous crack path with higher impact velocity. The SiC and forsterite phases generate during heat treatment are advantageous in inhibiting crack propagation, while the formation of oxide layer makes the material more susceptible to brittle fracture. Due to the presence of microcracks, high graphite samples lead to a reduction in tensile strength, but result in a wider fracture zone, which dissipates impact energy. Compared with the significant increase of strength under compressive impact loading, the critical tensile strain rate of MgO-C is easier to achieve after which the tensile strength decreases.