High Velocity Impact Loading Research Articles

The Impact Performance of Woven-Fabric Thermoplastic and Thermoset Composites Subjected to High-Velocity Soft- and Hard-Impact Loading

The present paper investigates the impact performance of woven-fabric carbon-fibre composites based upon both thermoplastic- and thermoset-matrix polymers under high-velocity impact loading by conducting gas-gun experiments at impact velocities of up to 100 m.s−1. The carbon-fibre reinforced-polymers (CFRPs) are impacted using soft- (i.e. gelatine) and hard- (i.e. aluminium-alloy) projectiles to simulate either a soft bird-strike or a hard foreign-body impact (e.g. runway debris), respectively, on typical composites employed in civil aircraft. The out-of-plane displacements of the impacted composite specimen are obtained by means of a three-dimensional Digital Image Correlation (DIC) system for the soft-projectile impact on the composites and the extent of damage is assessed both visually and by using portable C-scan equipment. The perforation resistance and energy absorbing capability of the composites are also studied by performing high-velocity impact experiments using the hard-projectile and the resulting extent and type of damage are identified. In addition, a Finite Element (FE) model is also developed to investigate the interaction between the projectile and the composite target.

The effect of hybridization on high-velocity impact response of carbon fiber-reinforced polymer composites using finite element modeling, Taguchi method and artificial neural network

In this paper, the effect of hybridization of carbon fiber-reinforced polymer (CFRP) composite laminates was investigated on the high-velocity impact responses of laminates using a validated finite element model, the Taguchi and the artificial neural network methods. The CFRP laminates were hybridized by replacing half of the carbon layers with glass and Kevlar laminae. It was found out that employing the right hybrid materials on the right position of the laminate can considerably change the damage pattern and consequently reduce the projectile residual velocity by increasing the energy absorbed by the CFRP laminate. Introducing four Kevlar laminae on the back of the CFRP composite laminate instead of the four carbon layers resulted the highest improvement in the laminate energy absorption by 67%. The hybrid laminates experienced wider damage zone and more extensive delamination compared to the CFRP laminate. Introducing the hybrid materials with high strength and strain to failure material such as Kevlar on the back of the laminate in the presence of CFRP front face can be considered as an appropriate hybrid composite laminate when exposed to high-velocity impact loading.

Highly Reactive Prestressed Aluminum under High Velocity Impact Loading: Processing for Improved Energy Conversion

Harnessing greater power from metal particle combustion requires engineering the core‐shell particle structure to more rapidly release stored chemical energy upon ignition. This study examines the metallurgical process of prestressing to increase the strain inside aluminum (Al) particles, then links increased strain to altered reaction mechanisms under high velocity impact. Results show that the quenching rate during prestressing changes the Al reaction mechanism. At faster quenching rates (900 K min−1), roughly 50% of the interfacial surface between the Al core and Al2O3 shell delaminates based on a model developed to understand the measured strain. Without core reinforcement, the shell fractures readily upon impact causing dramatically increased ignition sensitivity (measured in terms of pressurization rate) and reactivity (measured in terms of flame spreading). For slower quenching rates (200 K min−1), the core‐shell interface remains intact but strain in the particle increases by an order of magnitude. In addition, elastic stiffness in the shell may increase during prestressing. Increased elastic stiffness can effectively reduce ignition sensitivity and higher strain may contribute energy toward the nearly 40% increase in reactivity for the slower quenched aluminum powder. These results establish a link between altering mechanical properties of particles and their ignition and reactivity under dynamic loads.

A new damage-based nonlocal model for dynamic tensile failure of concrete material

When concrete structures subjected to the blasts and high velocity impact loadings, dynamic tensile failure (e.g. spall) is frequently observed. It is known accurate prediction of dynamic tensile failure is a challenging problem. In the present study, a new damage-based nonlocal model is proposed to predict the dynamic tensile failure of concrete material, which is based on the local Kong-Fang concrete material model recently proposed (Int J Impact Eng 2018, 120: 60–78). In this nonlocal model, the interaction domain decreases with the increase of local damage, which leads to a desirable description of the localization at total damaged regions and free surfaces, i.e., non-localities vanish at these regions. Numerical examples of a 1D spalling test and a 2D dynamic tension test of a concrete plate demonstrate that the damage-based nonlocal model can resolve all the limitations of original nonlocal models. The damage based nonlocal model is then validated against two experiments, namely, the Split Hopkinson Tensile Bar (SHTB) test and the Modified Split-Hopkinson bar (spalling) test. Numerical simulations show that, the proposed nonlocal model can reasonably predict the dynamic tensile failure location. But the local model cannot correctly predict the dynamic tensile failure, and the original nonlocal model cannot predict the multiple cracks under intense loading rate.

Research on Ferromagnetic Hysteresis of a Magnetorheological Fluid Damper

The inherent hysteresis of magnetorheological fluid dampers is one of the main reasons which limit their applications. The hysteresis mainly caused from two aspects. One part of the hysteresis is between the damping force and the piston velocity, which induced from the friction force of the damper, the compressibility of the fluid, rheological behavior etc. Another part of the hysteresis is between the damping force and the control current, which induced from the ferromagnetic materials inside the MR fluid damper. The ferromagnetic hysteresis of the MR fluid damper has been paid little attention to for a long time. Currently, the MR fluid damper is applying to the field of high velocity or shock and impact loadings where ferromagnetic hysteresis reduces the performance of the control current which leads to worse performances of vibration or buffer. Hall sensors are embedded to the MR fluid damper in this paper so that the magnetic flux density of the damping channels can be measured in real time. The hysteresis loops of the damping channels are obtained by measuring the relationships of the magnetic flux densities and the control currents. Furthermore, a Jiles-Atherton (J-A) hysteresis model based on differential equations for the MR fluid damper is established. The J-A hysteresis model is according to the domain-wall theory so that it has clear physical meaning with a small number of parameters. The hysteresis model is simulated utilizing MATLAB/SIMULINK. The particle swarm optimization (PSO) is adopted to identify the parameters of the J-A hysteresis model. The results show that the hysteresis loops identified by PSO is more similar to the measured hysteresis loops compared with the traditional parameter identification method. The research in this paper on the characteristic and model of the ferromagnetic hysteresis of the MR fluid damper is benefit to decrease or eliminate the effects of hysteresis which can improve the performances of the MR fluid dampers.

Weak-shock wave propagation in polymer-based particulate composites

Shock waves are common in polymer-based particulate composites that are subjected to intermediate to high-velocity impact loading. However, quantitative information on the spatial variation of stress, particle velocities, and energy dissipation during the formation and propagation of weak-shock waves is limited. In this paper, a systematic experimental study is conducted to understand the characteristics of weak-shocks in polymer-bonded particulate composites. Specimens made of polymer-bonded sugar are subjected to a projectile impact loading, at varying velocities, using a modified Hopkinson pressure bar apparatus. Full-field displacement and strains of the deformed samples are obtained with the help of an ultrahigh-speed imaging and digital image correlation technique. Using the full-field displacement data, the shock wave velocity, shock front thickness, and the full-field stress fields are calculated. From the spatial stress field and the strain rate data, the spatial energy dissipation profile is also estimated. The effect of impact velocity on the spatial stress profile, shock wave velocity, and energy dissipation are discussed.

Relationships between shock stress and electrical output characteristics for PZT-5H under high-velocity impact loading

To disclose the electrical output characteristics of PZT-5H piezoelectric ceramic with 50 ohm resistor as a electrical output load at the condition of different projectile’ ratios of length to diameter and high-speed impact loading. The one-stage light gas gun loading system, shock stress testing system and the electrical output testing system were constructed by ourselves in laboratory. Experiments have been performed to research cylindrical 2A12aluminum projectile (different ratios of length to diameter) vertically impacting on PZT-5H piezoelectric ceramic composite targets at the different impact velocities. The experimental results showed that the duration of the stress wave on the piezoelectric ceramic increased with the increasing of ratio of length to diameter for the projectile, however the piezoelectric ceramics could continue to supply power with the increasing of ratio of length to diameter for the projectile after the stress wave was unloaded. The phenomenon of charge leakage did exist during the the process of interaction between the projectile with a large ratio of length to diameter and the piezoelectric ceramic composite targets, and the duration of voltage output pulse became shorter due to the influence of leakage current. The shock stress peaks of PZT-5H piezoelectric ceramic composite targets reaches several hundred MPa in pulse width of 30 μs, and part of the piezoelectric ceramic was completely depolarized, and the peak of voltage pulse generated was 580 V across a load resistor of 50 ohms, meanwhile energy output up to 30mJ within 10 μs.

High velocity impact behavior of Kevlar/rubber and Kevlar/epoxy composites: A comparative study

This paper presents a comparison of behavior and energy absorption of neat Kevlar fabric and polymer matrix composites under high velocity impact loading. Two types of matrices including rubber and thermoset (epoxy) matrices were used in order to study the effect of a hard and brittle matrix compared with the soft and flexible matrix on energy absorption of the composite. Moreover, two types of rubber matrix with high hardness (HH) and low hardness (LH) were used in this study to investigate the effect of rubber matrix formulation on impact resistance of composites. Ballistic impact tests were performed by firing a 10 mm hemispherical projectile onto neat fabric and composites in a velocity range of 30–150 m/s for two- and four-layer samples. Results show that the matrix affects the ballistic performance of composites significantly. Rubber matrix enhances the energy absorption of the fabric by keeping composite flexibility. Increase the number of layers for Kevlar/rubber composite results in better ballistic performance. On the contrary, the thermoset matrix leads to an inflexible composite that restricts the fabric deformation and has a negative effect on the fabric’s ballistic performance. Finally, damage mechanisms were discussed in detail for each sample.

Effect of Hostile Solutions on Composites Laminates Subjected to Low and High Velocity Impact Loads

Composite structures can be exposed to different hostile environments, which cause degradation of their mechanical properties. However, this subject is not completely understood. Therefore, the aim of the present work is to study the low velocity impact and the response at high strain rates of carbon/epoxy laminates, after immersion into hydrochloric acid (HCl) and sodium hydroxide (NaOH). From the experimental tests, it is very clear that exposure to corrosive solutions affects significantly the impact strength, but their effects are strongly dependent of the exposure time. Finally, alkaline solutions show to be more aggressive.

Ballistic performance of Kevlar fabric impregnated with nanosilica/PEG shear thickening fluid

This study presents the response of fiber reinforced composite material composed of woven Kevlar fabric impregnated with a colloidal shear thickening fluid (STF) under high velocity impact loading. The STF was made by dispersing silica nanoparticles at 15, 25, 35 and 45 wt.% loading in polyethylene glycol. The effects of silica nanoparticle loading on energy absorption and ballistic limit were studied experimentally. Rheological results revealed that shear thickening occurred at all four nanosilica loading and higher loading showing the higher shear thickening at lower shear rate. SEM images confirmed good dispersion of nanosilica particles in the suspension. The results of the pull out test show that by increasing nanosilica loading, the force required to pull the yarn out from the fabric impregnated by STF increases. Impact resistance performance of Kevlar fabric is significantly enhanced due to the presence of STF. Although high velocity impact results show that by increasing nanosilica loading, the energy absorption of composites increases, but in high loading of nanosilica, the effectiveness of STF decreases. For further investigation, the energy absorption at the ballistic limit was normalized by the areal density of the neat and impregnated fabrics to give the specific energy absorption (SEA). It is found that the SEA of 15 wt.% nanosilica loading is lower compared to the neat fabric. Also the highest SEA turn out in the case of 35 wt.% STF/Kevlar composites in which the SEA is 2.3 times larger than those of the neat fabric.

In-plane dynamic crushing behaviors of a novel auxetic honeycomb with two plateau stress regions

In order to obtain honeycomb structure with higher energy absorption capacity, a novel honeycomb is proposed by adding double arrowhead honeycomb (DAH) cells into star-shaped honeycomb (SSH), and therefore named as star-arrowhead honeycomb (SAH). An analytical model is built to investigate the in-plane elastic properties of the newly proposed honeycomb and the results are in good agreement with the finite element simulations. The in-plane dynamic crushing behaviors and energy absorption capabilities of SAH are studied systematically by finite element method and are compared with that of SSH and DAH. Two plateau stress regions in the stress–strain curves of SAH are observed under low-velocity impact loading, and the second plateau stress is over three times higher than the first one. The in-plane Poisson's ratio of SAH under static and high-velocity impact loading always shows negative value. However, the Poisson's ratio of SAH changes from negative to positive under low-velocity and medium-velocity impact loading. In addition, the Poisson's ratio of SSH and DAH are negative during the entire dynamic deformation processes. The results of finite element simulations show that SAH can absorb much more energy than SSH with the same relative densities under different impact velocities, especially under low-velocity impact loading. Furthermore, the effects of the cell wall thickness and the impact velocity on plateau stress of SAH are discussed, and therefore a deformation map is summarized. It can be concluded that SAH is a better choice for energy absorption. This study may provide a new design concept for the high performance honeycomb structure with multi plateau stress regions.

Numerical and experimental study of impact on hyperelastic rubber panels

This study presents the response of rubber panels subjected to high-velocity impact loading. The mechanical properties and impact performance of rubber panels are altered by the variation in compound ingredients. To investigate the effect of compound ingredients, two types of rubber panels with high (SHA70) and low hardnesses (SHA45) were prepared, and mechanical properties and impact resistance of the panels were measured by high-velocity impact tests in a velocity range of 70–160 m/s. Ballistic limits of about 80 and 94 m/s were obtained for the low- and high-hardness rubbers, respectively, which show that the energy absorption of rubber panels increases as filler loading content increases. In this respect, the finite-element simulation has been performed to investigate the ballistic performance of rubber panels numerically. Rubber panel has been modeled using the LS-DYNA software and employing the experimental results of tensile test to characterize the behavior of panel. The findings show a good agreement between the numerical and experimental data. To study the effect of projectile’s shape, impact resistance of the rubber panels against hemispherical projectiles with different length-to-diameter (L/D) ratios (projectiles with diameters of 8, 10, and 12 mm) was measured and the model was also used. The results demonstrate that energy absorption of the panel increases as the diameter of projectile increases. The energy absorbed by the rubber panels appears in the form of damages that lead to increase their damage zone.

State-of-the-Art Finite Element Modeling of Rotorcraft Main Rotor Blade for Bird Strike Damage Analysis

This paper demonstrates the state-of-the-art composite modeling methodology to investigate the bird strike phenomenon using available numerical bird models through experimental tests and simulation tools. The present work is based on the application of nonlinear explicit finite element analysis to simulate the response of rotorcraft main rotor blade root end under high velocity impact load. The damage behavior of blade made of composites under soft body impact depends upon bird size, blade size, blade span-wise location of impact and bird orientation with respect to hitting location, blade rotational speed and rotorcraft cruise speed. Bird model is considered as hydrodynamic with length-to-diameter ratio of 2. A bird strike event is characterized by loads of high intensity and short duration. A transient explicit nonlinear finite element-based impact analysis using Autodyn has been carried out to predict bird strike resistance to withstand 1.0 kg bird at critical flight condition. Numerical analysis indicates that blades do not tear which agrees well with the physical test conducted.

Response of UHPFRC and HDFRC under static and high-velocity projectile impact loads

This paper presents an experimental investigation of the mechanical properties of ultra-high-performance fiber-reinforced concrete (UHPFRC) and high-ductile fiber-reinforced composite (HDFRC) under a static load and of the impact resistance capacity of both materials under a high-velocity projectile impact load. Two types of materials, i.e., strength-oriented UHPFRC and ductility-oriented alkali-activated slag-based HDFRC, were designed and prepared. A series of experiments, including a compressive strength test, a uniaxial tension test, and high-velocity projectile impact test, were conducted to characterize the properties of the materials. From the test results, it was found that the UHPFRC mixture with a compressive strength of 155 MPa and a tensile strain capacity of 1.04% has toughness under a static tensile load similar to that of the HDFRC mixture with a compressive strength of 32.9 MPa and a tensile strain capacity of 7.9%. Although the UHPFRC mixture has a slightly higher resistance capacity to high-velocity projectile impact loads in terms of the failure mode, mass loss, crater area, and penetration depth compared to the HDFRC mixture, both materials showed higher impact resistance capacities than that predicted by the empirical model.

High Velocity Impact and Blast Loading of Composite Sandwich Panels with Novel Carbon and Glass Construction

This research investigates whether the layup order of the carbon-fibre/glass-fibre skins in hybrid composite sandwich panels has an effect on impact response. Composite sandwich panels with carbon-fibre/glass-fibre hybrid skins were subjected to impact at velocities of 75 ± 3 and 90 ± 3 m s−1. Measurements of the sandwich panels were made using high-speed 3D digital image correlation (DIC), and post-impact damage was assessed by sectioning the sandwich panels. It was concluded that the introduction of glass-fibre layers into carbon-fibre laminate skins reduces brittle failure compared to a sandwich panel with carbon-fibre reinforced polymer skins alone. Furthermore, if the impact surface is known, it would be beneficial to select an asymmetrical panel such as Hybrid-(GCFGC) utilising glass-fibre layers in compression and carbon-fibre layers in tension. This hybrid sandwich panel achieves a specific deflection of 0.322 mm kg−1 m2 and specific strain of 0.077% kg−1 m2 under an impact velocity of 75 ± 3 m s−1. However, if the impact surface is not known, selection of a panel with a symmetric yet more dispersed hybridisation would be effective. By distributing the different fibre layers more evenly within the skin, less surface and core damage is achieved. The distributed hybrid investigated in this research, Hybrid-(GCGFGCG), achieved a specific deflection of 0.394 mm kg−1 m2 and specific strain of 0.085% kg−1 m2 under an impact velocity of 75 ± 3 m s−1. Blast loading was performed on a large scale version of Hybrid-(GCFGC) and it exhibited a maximum deflection of 75 mm following a similar deflection profile to those observed for the impact experiments.

Research on dynamic response characteristics of CFRP/Al HC SPs subjected to high-velocity impact

Abstract CFRP/Al HC SPs (Carbon Fiber Reinforced Plastic/Aluminum Honeycomb Sandwich Panels)composite structures are widely used in the aerospace and many other fields due to their excellent performances. In order to reveal profoundly the dynamic response characteristics of CFRP/Al HC SPs composite structure under high-velocity impact loading, the experiments about aluminum honeycomb core and CFRP/Al HC SPs composite structure impacted by high-velocity projectiles have been performed by using a one-stage light gas gun loading and a high-speed camera systems, respectively. The whole physical process of collision is analyzed by using TEMA software which is provided by high-speed camera's manufacturer, and the pictures and related physical parameters of the projectile passing through the different layers at the key moments are extracted based on the set frame rate of the video. Meanwhile, the ABAQUS/Explicit module was used to conduct numerical simulation under the same conditions as the experiments, and extracting the pictures and related physical parameters during the projectile penetrating through aluminum honeycomb core and the sandwich panels at the different key moments. The results show that the durations of action for the projectile impacting the Al HC core and the CFRP/Al HC SPs at the velocity about 280 m/s were 86 μs and 240 μs in experiments, respectively, and the durations of action were 90.7 μs and 236.2 μs at the same experimental conditions in numerical simulation, which were basically consistent comparing the experimental to simulated results. Moreover, more than 70% for the kinetic energy of the projectile consumed by the sandwich panels was attributed to the front panel and the aluminum honeycomb core during the entire impact process, and all these have verified the reliability of the numerical simulation.

An experimental study on the effect of adding multi-walled carbon nanotubes on high-velocity impact behavior of fiber metal laminates

In this paper, the effect of adding multi-walled carbon nanotubes (MWCNTs) on high-velocity impact behavior of fiber metal laminates (FMLs) was investigated. The unreinforced and reinforced FMLs with different MWCNT weight percentages of 0.25, 0.5 and 1 were manufactured and tested under high-velocity impact loading using a gas gun and a spherical projectile. Moreover, tensile tests were performed on the unreinforced and reinforced composite laminates of FMLs. Incorporating 0.5 wt% of MWCNTs into the composite laminate of FML resulted the maximum reduction of 29.8% in projectile residual velocity and the maximum increase of 18.9% in the absorbed energy during projectile perforation compared to the unreinforced FMLs. This was consistent with the tensile test results in which maximum improvements in the strength, stiffness and toughness were obtained for the 0.5 wt% MWCNT-nanocomposite. The detailed visual inspections and SEM images showed that adding MWCNTs improved the resin-fiber adhesion consequently reduced the composite delamination and matrix cracking. Conversely, MWCNTs weakened bonding between the aluminum and composite layers and allowed the aluminum layer to experience larger plastic deformation.

Shock Response of Lightweight Adobe Masonry

The behavior of a low density and low-strength building material under shock loading is investigated. The considered material is lightweight adobe masonry characterized by a density of 1.2 g/cm3 and a quasi-static uniaxial compressive strength of 2.8 MPa. Planar-plate-impact (PPI) tests with velocities in between 295 and 950 m/s are performed in order to obtain Hugoniot data and to derive parameters for an equation of state (EOS) that captures the occurring phenomenology of porous compaction and subsequent unloading. The resulting EOS description is validated by comparing the experimental free surface velocity time curves with those obtained by numerical simulations of the performed PPI tests. The non-linear compression behavior, including the pore compaction mechanism, constitutes a main ingredient for modelling the response of adobe to blast and high-velocity impact loading. We hence present a modeling approach for lightweight adobe which can be applied to such high rate loading scenarios in future studies. In general, this work shows that PPI tests on lightweight and low-strength geological materials can be used to extract Hugoniot data despite significant material inhomogeneity. Furthermore, we demonstrate that a homogenous material model is able to numerically describe such a material under shock compression and release with a reasonable accuracy.

The modelling of impact loading on thermoplastic fibre-metal laminates

This work presents the findings of a study to investigate the modelling of impact loading on fibre-metal laminates based on an innovative self-reinforced thermoplastic composite reinforcement manufactured from polypropylene. A finite element model of the thermoplastic fibre metal laminate (TFML) has been developed using the LS-Dyna software package, with input from data collected following mechanical tests conducted over a wide range of strain-rates. Plates having different stacking sequences were modelled numerically under both low and high velocity impact loading, where the effect of varying stacking sequence and the thickness of the constituent material were investigated. An improved TFML configuration is proposed which, when impact energy absorption is considered, should outperform both commercial FMLs as well as monolithic aluminium alloys. It is believed that these environmentally-friendly thermoplastic-based materials offer potential for use in lightweight structures subjected to impact loading, such as aircraft leading edges and automotive body panels.

Experimental damage evaluation of honeycomb sandwich structures with Al/B4C FGM face plates under high velocity impact loads

In this experimental study, high velocity impact behavior of honeycomb sandwich structures with Al6061/B4C FGM face plates subjected to 0.30 caliber fragment simulating projectile impact was investigated via a single-stage gas gun. The material composition of the FGM face plates was represented according to a power-law variation through the plate thickness. The specimens were produced for six types of face plates, Al6061 and five different FGM face plates from metal-rich to ceramic-rich composition. Impact test results of the specimens were evaluated in terms of their damage and deformation mechanisms. The test results stated that the material composition variation of the FGM face plates was a highly influential parameter for damage modes, energy absorbing capacity, and impact resistance of the sandwich structure, and the honeycomb core contributed to the energy absorbing capacity of the sandwich structure with the plastic buckling of the cell walls and lateral crushing deformations.