High Velocity Impact Research Articles

High-velocity impact studies of honeycomb sandwich structures with Al/Al2O3 and Al/B4C functionally graded plasma sprayed faceplates

High-velocity impact response of honeycomb sandwich structures (HSS) with Al/Al2O3 and Al/B4C functionally graded plasma-sprayed (FGPS) faceplates are investigated in present work. FGPS structures improve the specific material properties and make the structure distinct from the substrate material. The metal and ceramic content was varied across the thickness of the FGPS coating in the present work. The HSS having honeycomb core sandwiched between two Al/Al2O3 FGPS faceplates were manufactured initially. Further, HSS having honeycomb core sandwiched between two Al/B4C FGPS faceplates were manufactured. Such HSS are repeatedly impacted with a spherical projectile using a single-stage gas gun at a constant impact energy of 260 J, and the results are quantified and compared. The central deflection and dent diameter of FGPS plates as well as HSS were determined, and they increased with the number of impacts. The HSS’s energy absorption was dissipated by top faceplate indentation and core compression. The incorporation of a core prevented FGPS coating delamination and top faceplate penetration. The Al/Al2O3 and Al/B4C FGPS faceplates had dent diameters that were 14.30% and 18.70% smaller than the non-coated Al 6061-T6 faceplate, respectively, which proves the enhancement of high-velocity impact resistance through FGPS coating. The central deflection and dent diameter of the Al/B4C FGPS HSS are 6.04% and 3% lesser than the Al/Al2O3 FGPS HSS, respectively. The energy absorption of the Al/B4C FGPS HSS is better than that of the Al/Al2O3 FGPS HSS. As a result, the present research enhances the knowledge on the impact energy absorption of two distinct FGPS coated plates and HSS, which is highly useful in aerospace and defence applications.

Investigation of energy absorption in epoxy-based Aramid fabrics -Basalt hybrid composites under oblique high velocity impact

Investigation of energy absorption in epoxy-based Aramid fabrics -Basalt hybrid composites under oblique high velocity impact

Experimental and numerical investigations on the mechanical behavior of composite pre-tightened tooth connection under impact loading

The composite Pre-Tightened Tooth Connection (PTTC) is characterized by high connection efficiency and large bearing capacity, specifically designed for use in fiber-reinforced polymer (FRP)-metal protective structures that are inherently subjected to impact loads. In this study, impact tests were performed on single- and double-tooth specimens under high-velocity impact loads using the Split Hopkinson Pressure Bar (SHPB) apparatus to investigate their impact behavior. Additionally, a progressive damage model was numerically developed and validated against the experimental results to examine the failure patterns and mechanisms of the PTTC. The effects of tooth depth, tooth length, number of teeth, and impact velocity on the impact behavior were also analyzed parametrically. The results indicated that the primary failure modes of the PTTC are ductile compression-shear failure and brittle shear failure. In cases of compression-shear failure, the bearing capacity is lower than that of shear failure; however, it exhibits superior energy absorption characteristics. Therefore, it is recommended that the PTTC be designed to facilitate compression-shear failure when subjected to high-velocity impact. The length, depth, and number of teeth significantly influence the failure mode, bearing capacity, and energy absorption of the PTTC. Adequate design attention should be given to these factors for applications involving impact loads.

Effects of surface curvature on rain erosion of wind turbine blades under high-velocity impact

Rain erosion induced by raindrops impacting wind turbine blades at high velocity can change the aerodynamic characteristics of the blades and increase maintenance costs. Previous numerical studies on rain erosion have not considered the curvature of the blade leading-edge surfaces and assumed them to be flat surfaces. This study established a fluid-solid coupled numerical model combining the finite element method and smooth particle hydrodynamics. It models a water droplet with a diameter of 2.74 mm impacting the curved leading-edge surface of wind turbine blades with radii of curvature of 1.35 mm, 6.75 mm, 67.5 mm, and infinite at 110 m/s, and the effects of the radius of curvature on the impact response were analyzed. The results show that as the radius of curvature of the leading-edge surface increases, the surface obstructs the water droplet more significantly, and the lateral jetting of the water droplet is enhanced. A larger radius of curvature causes more droplet impact energy to be transferred to the curved surface, increasing the contact force between the water droplet and the surface. The increased transferred impact energy results in higher stress and plastic strain values. The decrease in the radius of curvature of a curved surface increases the error in the stress and strain results obtained by assuming it to be a flat surface.

Grain refinement in metal microparticles subjected to high impact velocities

Grain refinement in metal microparticles subjected to high impact velocities

Deposition behavior of the gas-atomized 7075Al and TiB2/7075Al composite powders during cold spraying

To fabricate high-quality coatings or components of high-strength 7075Al alloy by cold spraying, it is essential to understand the impact behavior and bonding mechanisms of the feedstock powder particles. For providing a general comparison, 7075Al powder and TiB2/7075Al composite powder (7075Al alloy matrix reinforced with in-situ formed and uniformly dispersed nano-TiB2 particles) produced by gas-atomization were used as feedstocks in the present study. Single particle impact tests combined with finite element analysis (FEA) were performed on the pure Al and 7075Al-T6 substrates under different process parameter sets. To provide a more realistic description, the real powder strength and plastic parameters obtained by single-particle compression tests were used as input data in the FEA model. The results show that the presence of nano-TiB2 particles has significant strengthening effects on the composite powder, thus resulting in different plastic deformation behavior upon impact compared to 7075Al powder. When the composite particles impacted the soft material (pure Al), the substrate experienced a high degree of deformation, which led to high deposition efficiency due to the embedding effect. Comparatively, the hard substrate (7075Al-T6) was less deformed, whereas the composite particle was highly deformed. Compared to the composite particle, the 7075Al particle presented a slightly higher plastic deformation and pronounced metal jets, which led to a lower critical impact velocity for successful bonding. Interestingly, a fracture was observed at the grain boundaries of both 7075Al and TiB2/7075Al composite particles in the case of a high gas temperature regime, which probably revealed that the high shock energy associated with high-velocity impact led to such intergranular fracture.

High-velocity impact behavior of scarf-repaired composite laminates

High-velocity impact behavior of scarf-repaired composite laminates

Mechanical characterization of intact rock under polyaxial static-dynamic stress states

Accurate assessment of mechanical behaviour of rock is essential for safe and efficient design of structures on or within rock mass particularly under harsh in-situ stress conditions. Insights from rock engineering practices have revealed that rockbursts can occur at various scales and at any time during mining activities. These violent failure phenomena can be triggered by quasi-static stress redistribution resulting from mining activities as well as dynamically induced loads from seismic events. Moreover, the mechanical behaviour of rock has proven to differ under static and dynamic stress conditions, showing rate-dependent characteristics. Hence, this study aims to thoroughly investigate the triggers that can lead to rockburst events and provide insights into the brittle fracturing process under various stress conditions. To achieve this, a comprehensive set of static and dynamic laboratory tests was conducted on coal samples. The static experiments were conducted under uniaxial and triaxial conditions where the samples were tested at the confining pressures up to 20 MPa. For the dynamic tests, the samples were first pre-stressed uniaxially, biaxially and polyaxially at different ranges of static stresses up to 30 MPa hydrostatically and non-hydrostatically. Then, the high impact velocity up to 21.5 m/s was applied along the maximum stress direction to provide dynamic loading. The influences of loading condition, strain rate and confinement on the mechanical behaviour of coal were investigated. The fracturing process of samples based on their uniaxial, biaxial and polyaxial pre-stressing conditions and various strain rates were analysed to confirm the significant role of loss of confinement and strain rate in severe high-energy fragmentation of coal or so-called “rockburst” under both static and dynamic loadings.

High velocity impact performance of double ceramic stacking on multilayer sandwich armor structures

High velocity impact performance of double ceramic stacking on multilayer sandwich armor structures

Mechanical characterization and impact damage assessment of Al/SiC functionally graded coating under elevated temperatures

Functionally graded materials are a class of composite materials that finds widespread use in aerospace, defense and automobile applications due to their tailored material properties for the specific need. In the present research, impact dynamics and the damage behavior of functionally graded plasma spray coating (FGPS) on an aluminium 6061-T6 substrate under high velocity impact at various temperatures were studied. The FGPS coating consists of four layers having various proportions of Al and SiC (50/50, 40/60, 30/70 and 20/80 weight percentages) and the coating thickness was measured to be 232.8 μm. Experiments were carried out at 260 J of impact energy on the FGPS samples at various temperatures using a single-stage gas gun along with the thermal setup. A finite element model was developed with the Johnson-Cook damage model and piecewise linear plasticity material model, along with suitable contact algorithms. Impact simulations at various temperatures reveal that the stiffness reduction at higher temperatures results in decreased peak contact force, decreased rebound velocity and increased central deflection. The molten splats observed through the micro-morphological study have spread several micrometers, which indicates excellent bonding between the particles and the porosity content was found to be 1.35%. The research findings on the impact dynamics and damage behavior of FGPS can significantly improve material design for a wide range of applications.

Experimental biomechanical investigation of surrogate headforms equipped with Patka helmet against high-velocity ballistic impact

High-velocity bullet impact (velocity: 700 ± 15 m/s) is a significant concern during asymmetric warfare. Ballistic helmets for high-velocity bullet impact and associated biomechanical responses of the headforms are actively sought. Further, data on the performance of ballistic helmets against high-velocity impact are not available in the literature. Toward this end, we have evaluated the performance of Patka (helmet) against high-velocity bullet impact. Patka was mounted on various headforms to assess the perforation of the Patka by the bullet and to measure various biomechanical parameters such as back face deformation (BFD), head kinematics, brain simulant pressures, and neck loads. Bullet impact in front and oblique (30° right to the sagittal axis) orientations were considered. Our results suggest that the Patka was effective in mitigating the high-velocity bullet impact. Perforation of the Patka by the bullet was not observed. BFD in the witness material was negligible (<1 mm). Measured head kinematics and brain simulant pressures were comparable to the quantities typically reported during low- and medium-velocity bullet impacts. Further, most of the biomechanical responses, except angular acceleration and neck force, were below 50% injury risk for mild traumatic brain injury (mTBI). Despite these encouraging trends, the shattering of bullets into fragments was also observed. These fragments traveled a considerable distance at reasonable velocities. This work provides unique insights regarding the performance of Patka and associated biomechanical responses of the headforms against high-velocity bullet impact, with implications in the design and evaluation of futuristic ballistic helmets. TERMINOLOGIES Ballistic threat level: Ballistic threat levels are defined based on the impact velocity of the bullet. Different types of bullets are proposed to achieve the desired impact velocities corresponding to different ballistic threat levels. Ballistic helmet: Ballistic helmet is a type of protective headgear designed to protect the wearer head from potentially fatal impacts during combat operations. Ballistic performance: Ballistic performance of the helmet is evaluated based on the perforation resistance capacity of the helmet and back face deformation (BFD) of the helmet. Back face deformation (BFD): Back face deformation (BFD) of the helmet refers to the localized dent or bulge in the inner layer of the helmet due to ballistic impact. BFD is measured as a depth of indent in the witness material (e.g., Roma Plastilina #1 clay) of the cruciform cavity-based headform. Headform: Headform is a model of the human head replicating a few of the anatomical and material aspects. Headforms can vary in design and complexity based on the intended applications. Patka: Patka is a protective headgear designed to provide ballistic protection to the head against high-velocity threat (impact velocity: 700 ± 15 m/s). Patka is made up of hardened (armour) steel material. Head kinematics: Head kinematics refers to the motion of the head typically measured in terms of linear acceleration and angular velocity. Neck loads: Neck loads refer to the forces and moments experienced by the neck during a static or dynamic event. Brain simulant pressure: Brain simulant pressure is a hydrodynamic pressure generated within the brain simulant.

Research on the Dynamic Spreading and Wettability Characteristics of Droplets on Coal Dust.

The dynamics of droplets spreading on surfaces have been extensively studied across various influencing factors, necessitating an exploration of their effect on wettability. Herein, the specific composition, size distribution, and contact angle of the coal dust preparation were characterized by a series of experiments to determine the conditions for the simulation. Meanwhile, the multiphase volume of the fluid method was implemented in the simulations, predicated on appropriate boundary conditions, and verified by a mesh independence test. The findings confirmed that the numerical approach for contact angle validation had a minor deviation, making it suitable for multiphase interface tracking. Besides, the typical wetting pattern of droplets was hereby identified into three stages, including the moving stage (stage I), the periodic wetting stage (stage II), and the balancing stage (stage III). The initial diameter could effectively increase the coverage area and spreading time for stage II. Obviously, the first amplitude of first maximum spreading diameter (D max-1) significantly increased with higher impact velocities, corresponding to an increase in kinetic energy. Despite the significant spreading effect of the falling height mainly on D max-1 and contact time, the increased trend of wetting efficiency was not obvious. However, the spreading factor and wetting efficiency decreased with increased roughness height. Finally, the difference in spreading wettability was illustrated based on the spreading wetting mechanism. The wetting efficiency of droplets on coal dust was remarkably influenced by the dynamic spreading behaviors of droplets. Overall, the findings from this study offer insights into the extent of spreading wetting that occurs before a droplet reaches an equilibrium state.

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

Study on the impact damage behavior and infrared radiation evolution characteristics of rock under different drop hammer velocities

Infrared radiation effectively monitors rock deformation and failure, playing a significant role in monitoring dynamic disasters such as rockburst and mine tremors. This study investigates rock fracture modes, mechanical properties, and infrared radiation responses under different impact velocities through drop hammer impact tests. The infrared thermal imaging and infrared radiation anomaly area characteristics during rock impact failure were quantitatively analyzed using infrared radiation frequency distribution. The results show that as impact velocity increases, the maximum impact force initially rises then stabilizes with a slight decrease; the double peak of impact force gradually centers on the first peak; the degree of damage increases before decreasing, with failure cracks gradually aligning with the central axis. The energy conversion rate exhibits a threshold, reaching a maximum of 95.54 % when the initial impact energy reaches 70.68 J. Infrared thermal imaging analysis reveals that the average infrared temperature increment (ΔAIRT) lags behind the maximum infrared temperature increment (ΔMIRT), with ΔMIRT being 43.74 times higher than ΔAIRT at higher impact velocities, and ΔMIRT and ΔAIRT being 3.57 and 6.88 times higher than those at lower impact velocities, respectively. The proportion of infrared radiation anomaly areas increases with impact velocity. At higher impact velocities, the low temperature anomaly area Pl reaches 0.104 %, while the high temperature anomaly area Ph reaches 0.0627 % (Plmax is approximately 3.5 times Phmax). The research findings are significant for assessing rock stability and identifying impact failure.

Peridynamic modeling of shocks and high-velocity impact with the Johnson-Holmquist-Beissel ceramic model

Peridynamic modeling of shocks and high-velocity impact with the Johnson-Holmquist-Beissel ceramic model

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.

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

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

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.

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