Spherical Steel Projectile Research Articles

The investigation of deflection behavior in carbon/epoxy and glass/epoxy composite laminates under low-velocity impact with small projectiles

This study examined the impact behavior of carbon/epoxy and glass/epoxy composite laminates with 2, 4, and 6 mm thicknesses under low-velocity tests. The investigation involved subjecting the composite laminates under small-impact loads using spherical, cylindrical, and conical steel projectiles, each weighing 3 g. The impacts conducted at 29.5, 36.5, and 51 m/s velocities. This investigation modeled using finite element (FE) methods and analytical approaches. In the analytical method, the mass and spring model used for the impact of small projectiles. The research findings revealed that, in 2 mm thick carbon/epoxy composite laminates, the maximum deflection at the mid-point induced by a spherical projectile was 1.37 mm. This value exhibited a 48.91% and 19.13% increase compared to impacts with cylindrical and conical projectiles, respectively. Additionally, a comprehensive examination of delamination across all samples indicated the maximum delamination occurrence in glass/epoxy samples, showcasing lower impact resistance than carbon/epoxy laminates. Notably, with an increase in thickness, the delamination phenomenon in the samples exhibited a decreasing trend. In addition, the maximum value of delamination in the composite laminates were with spherical, conical, and cylindrical projectiles respectively, and also, there was an excellent convergence between FE and analytical results.

High velocity steel spheres impact and damage analysis of graphene doped T700 composite shielding panels

Composite materials are increasingly being used in aircraft components such as fuselage panels which are subject to collision with debris during take-off/landing or in flight. This article provides an analysis of the impact resistance capability of graphene doped T700 (T700G) multilayer composite, when subjected to steel projectile impacts. Test coupons with 300×300 mm were impacted by steel spherical projectiles, with impact energies ranging from 34 J to 338 J, using a compressed air operated cannon. Test data, such as impact and absorbed energy were determined through impact and residual projectile velocity, acquired using ballistic chronograph and two high speed cameras. Damage assessment was performed using non-destructive techniques such as Ultrasonic testing before and after impact test. Through modelling and simulation, using ABAQUS/Explicit, and recording the change of projectile velocity, the energy loss of projectile is calculated, and the impact resistance is judged together with damage extent. T700G has similar impact resistance to AL2024, underperforming when impacted by larger projectiles and presenting an overall higher damaged area.

The impact‐induced deformation characteristics of polycarbonate panels

AbstractIn this study, the investigation of damage caused by a spherical steel projectile on the polycarbonate (PC) panels has been undertaken both numerically and experimentally. The material properties are obtained from both static and dynamic tests. High‐velocity impact experiments are performed using a pressure‐based projectile launching system. The effect of panel curvatures and impact locations on the deformation are investigated experimentally. The impact locations are selected as both at the plate center and near the edge of the plate. A validation study is performed by analyzing the impact response of a PC plate as previously presented in the literature and subsequently comparing it with the results obtained. An analysis of the impact behavior of PC panels is carried out through numerical simulations using finite element program (LS‐DYNA). The effect of boundary conditions on the impact response is also investigated numerically. Plastic strains, von Mises stresses, dent depth, and energy absorption are obtained. It is indicated by the results that the deformation behavior of PC panels exhibits a strain rate dependence. Additionally, the deformation behavior is influenced by panel curvatures and boundary conditions, emphasizing the necessity to consider these factors in the design of structures, such as canopies made of PC panels.Highlights Provides a comprehensive understanding of polycarbonate behavior. Emphasizes the influence of impact locations and panel curvatures. Dent depth and stress rise with panel curvature, crucial for design considerations. Emphasizes the significance of strain rate and boundary condition in design.

Experimental and numerical investigation on the compression after high-velocity impact behavior of composite laminates

Considering the differences in damage mechanism between high-velocity impact (HVI) and low-velocity impact (LVI), this study conducted HVI tests and compression-after-impact (CAI) tests to reveal the post-impact compression behavior of laminates manufactured by unidirectional prepreg tape and exposed a completely different mechanical response in residual strength compared to that of LVI. By controlling the impact velocity within the range of 200 m/s ̃ 380 m/s, three kinds of impact results were obtained, including un-penetrated and penetrated conditions. Different CAI damage morphologies can be observed in these laminates. In order to fully understand the CAI damage mechanism induced by different HVI events, a surface-based cohesive behavior and a CDM intralaminar damage model were implemented. In addition, a more complete picture of the compression behavior after HVI was observed through the simulation results, which is of great help in estimating the residual strength of post-impact laminates. However, the HVI damage was introduced through the spherical steel projectiles, and the sample size was determined based on ASTM D7137, which might be different factors from the application conditions.

High-velocity impact experiments and quantitative damage evaluation for finite ultra-high-performance concrete targets

In this work, we aim at improved characterization of target damage occurring as the result of projectile impact against ultra-high-performance concrete (UHPC). For this purpose, we present the results of high-velocity impact experiments with spherical steel projectiles and finite-thickness UHPC targets of approximately 115 MPa compressive cylinder strength in the impact velocity range from approximately 600 m/s to 1500 m/s. The data set obtained from these experiments includes residual projectile velocities as well as qualitative and quantitative information on damage. Quantitative damage information is mainly extracted from digital 3D post mortem targets, which are produced by 3D-scanning. For all damage quantities, a dependence on the impact velocity and the target thickness is discussed and used to provide possible explanations for the origin of the particular type of damage. The large data set presented in this work can constitute the basis for a comprehensive and quantitative verification and validation of analytical, empirical, and numerical models that describe the perforation of UHPC targets in the investigated impact velocity range.

Ballistic penetration of high-entropy CrMnFeCoNi alloy: Experiments and modelling

Ballistic impact experiments are conducted on a CrMnFeCoNi high-entropy alloy (HEA) using spherical steel projectiles, to investigate the penetration behavior in a wide range of impact velocities (∼800 to 2300 m s−1). Penetration processes are captured by high-speed camera. Postmortem samples are characterized via three-dimensional laser scanning, scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and microhardness tests. Both depth and diameter of impact crater show a nearly linear increase with increasing impact velocity. Penetration induces increased hardness; hardness is the same near the crater bottom and the sidewall, and the peak hardness (∼400 Hv1.0) is independent of impact velocity. The penetration-induced hardening is caused by multiple deformation defects including dislocations, twins and kink bands (KBs). Quantitative analysis further reveals that KB boundaries have a 5–50° misorientation angle, and their density decreases with increasing misorientation angle. KB boundary density is higher near the crater bottom than near the crater sidewall, while this trend is inverse for twinning boundary density. A finite element method model based on measured static and dynamic mechanical properties reproduces experimental observations and is used for interpreting deformation mechanisms.

Impact resistance and yarn pull-out behaviour of polymer spray-coated UHMWPE fabrics

The impact response of polymer spray-coated Ultra-high Molecular Weight Polyethylene (UHMWPE) plain woven fabrics has been studied. Several commercial spray coatings comprising various polymers and adhesives were used on the UHMWPE fabrics. Yarn pull-out tests revealed that the pull-out force significantly increased upon coating the fabric samples, and for rubber-coated samples the peak pull-out force increased by approximately 95 times that of the neat counterpart. Subsequently, two samples that exhibited the highest pull-out load per unit of areal density were selected for ballistic testing using a 12-mm (7.05 g) spherical steel projectile. Impact velocities of the projectiles were in the range of between 140 m/s and 230 m/s. Each sample consisted of four plies of either coated or neat fabrics. It was observed that rubber-coated samples showed the highest specific energy absorption when subjected to ballistic impact and perforation. The neat fabric targets were perforated purely by a wedge-through mechanism, whereas the coated samples were perforated by a combination of wedge-through and yarn failure mechanisms, with a considerable membrane effect. The enhanced pull-out force promoted the cohesive behaviour of the fabric by diminishing the windowing effect. A novel, highly computationally efficient numerical modelling approach was proposed which predicted the residual velocity, pull-out behaviour and the transverse deformation behaviour with high accuracy.

Ballistic impact response of flexible and rigid UHMWPE textile composites: Experiments and simulations

This study elaborates on the effects of matrix rigidity on the high-velocity impact behaviour of UHMWPE textile composites using experimental and numerical methods. Textile composite samples were manufactured of a plain-weave fabric (comprising Spectra® 1000 fibres) and four different matrix materials. High-velocity impact tests were conducted by launching a spherical steel projectile to strike on the prepared samples via a gas gun. The experimental results showed that the textile composites gradually changed from a membrane stretching mode to a plate bending mode as the matrix rigidity and thickness increased. The composites deformed in the membrane stretching mode had higher impact resistance and energy absorption capacity, and it was found that the average energy absorption per ply was much higher in this mode, although the number of broken yarns was smaller in the perforated samples. Moreover, the flexible matrix composites always had higher perforation resistance but larger deformation than the rigid matrix counterparts in the tested thickness and velocity range. A novel numerical modelling approach with enhanced computational efficiency was proposed to simulate textile composites in mesoscale resolution. The simulation results revealed that stress and strain development in the more rigid matrix composite was localised in the vicinity of the impact location, leading to larger local deformation and inferior perforation resistance.

Polyimide aerogels for ballistic impact protection

The ballistic performance of edge-clamped monolithic polyimide aerogel blocks (12 mm thickness) has been studied through a series of impact tests using a helium-filled gas gun connected to a vacuum chamber and a spherical steel projectile (approximately 3 mm diameter) with an impact velocity range of 150–1300 m s−1. The aerogels had an average bulk density of 0.17 g cm−3 with high porosity of approximately 88%. The ballistic limit velocity of the aerogels was estimated to be in the range of 175–179 m s−1. Moreover, the aerogels showed a robust ballistic energy absorption performance (e.g., at the impact velocity of 1283 m s−1 at least 18% of the impact energy was absorbed). At low impact velocities, the aerogels failed by ductile hole enlargement followed by a tensile failure. By contrast, at high impact velocities, the aerogels failed through an adiabatic shearing process. Given the substantially robust ballistic performance, the polyimide aerogels have a potential to combat multiple constraints such as cost, weight, and volume restrictions in aeronautical and aerospace applications with high blast resistance and ballistic performance requirements such as in stuffed Whipple shields for orbital debris containment application.

High-velocity projectile impact response of rubber-coated aramid Twaron fabrics

The impact response of aramid Twaron CT709 fabrics thinly coated with a commercially available spray-on rubber material has been studied for the first time. Both neat and rubber-coated fabric targets were subjected to impact using 12 mm, 7.05 g spherical steel projectiles. The impact velocities ranged from 150 to 250 m/s. Each target consisted of three plies of neat or coated fabrics. Residual velocities, impact velocities and transverse deformation profiles were recorded using a high-speed camera, and the mechanism of failure and energy absorption were studied. It was observed that the ballistic limit velocity (BLV) increased by 18% in the rubber-coated specimens compared with neat fabric specimens. A critical velocity (Vc) was established below which the coated targets absorbed higher energy than their neat counterparts. The rubber coating was found to promote a membrane effect with global deformation to failure leading to higher energy absorption than the neat counterparts. However, the coated samples absorbed lower energy for impact velocities greater than Vc. At these velocities, the rubber-coated specimens showed localised failure leading to lower energy absorption than the neat counterparts. A novel numerical modelling approach was proposed to simulate coated fabrics, and the models predicted the BLV with high accuracy (error < 4%).

Assessment of high-velocity impact effects on carbon fiber reinforced polymer sandwich panel with M-shaped core reinforced by nano-SiO2: Experimental and numerical study

This paper describes the high-velocity impact behavior of composite sandwich panels with different amounts of nano-SiO2. The sandwich panels were manufactured by carbon/fiber epoxy composite face sheets and an M-shaped core using the vacuum-assisted resin transfer molding method. To enhance the mechanical strength of the matrix, especially impact resistance, the nanoparticles were added to the resin epoxy matrix as filler with the ratios of 1%, 2%, and 3% of the composite's total weight. A scanning electron microscope was utilized to observe the microscopic structure of the composites, and it revealed an exceptional homogeneous mixture of nano-SiO2 particles in the resin epoxy matrix. Afterward, high-velocity impact tests were carried out using a single-stage gas gun test machine. A spherical steel projectile with a diameter of 8.7 mm was used for the test with a speed of 235 m/s. The experimental results indicated that adding 1–3 wt% of nano-SiO2 into the matrix remarkably increased the impact resistance of the composite. Moreover, the results showed that when the projectile collides with the core of the sandwich panel, it remains in the sandwich panel and its output velocity becomes zero, while when the projectile does not collide with the core, its output velocity is not zero. In order to validate the results, the experimental data were compared to the finite element models, and good agreement was observed.

A new partially-infused fiber reinforced thermoplastic composite for improving impact resistance

High toughness Kevlar fiber reinforced polymer composites are adopted for applications such as bulletproof shields, helmets and hard body armor that require high impact resistance as well as sufficient structural stiffness and strength. However, the impact energy absorption of fully-infused stiff composites made of Kevlar fibers and matrix is not as good as that of dry Kevlar fabrics. This study proposes a partially-infused Kevlar fiber reinforced thermoplastic laminate with significantly improved impact resistance. Unlike conventional Kevlar fiber reinforced laminates where the resin is fully infused into the fiber yarns, the fabrication process of partially-infused laminates is controlled such that only the exterior of the Kevlar fiber yarns is infused with thermoplastic resin. Consequently, the Kevlar fibers at the core of each fiber yarn are unrestricted during impact, thus, dissipating more energy. The infused exterior of Kevlar fiber yarns forms tough interlaminar interfaces that resist delamination during out-of-plane loading. The partially-infused laminate has similar static indentation resistance and slightly lower bending resistance when compared to conventional fully-infused Kevlar reinforced thermoplastic laminate, but dissipated 318% more energy in ballistic penetration tests performed with a 12 mm diameter steel spherical projectile.

A simplified Johnson-Cook model of TC4T for aeroengine foreign object damage prediction

Foreign object damage (FOD) was one of the major concerns of airworthiness requirements for aeroengines in service and maintenance, which reduced the fatigue life and led to premature failure. In present work, dynamic mechanical properties of a new titanium alloy named TC4T were firstly investigated by using Split-Hopkinson pressure bar (SHPB) tests at high strain rates and quasi-static tensile tests with different triaxiality. Based on experimental data, a simplified Johnson-cook (J-C) model with failure criterion was established to describe the strain-rate dependent constitutive model for TC4T. Finite element (FE) models to simulate SHPB and quasi-static tensile tests were developed and validated by experimental results, respectively, to evaluate the effectiveness of the J-C model. Excellent agreements could be found between numerical prediction and experimental results. Secondly, laboratory simulated FOD tests were carried out by air gun to launch steel spherical projectiles with various diameters impacting the edge of the flat plate specimen made of TC4T at different impact velocities. The corresponding 3D FE model was also developed and predicted FOD profiles were compared with experimental results. Satisfactory agreement could be obtained between numerical predictions and the experimental measurements. Finally, a full-scale 3D FE model of an aeroengine fan blade was established by using the proposed J-C model to predict and evaluate FOD. The effect of the initial stress state and impact position on FOD were investigated and results showed that the initial stress had less influence on the sizes of FOD profiles, while the impact position had a significant effect on FOD.

High-velocity impact resistance of doubly curved sandwich panels with re-entrant honeycomb and foam core

This work describes the high-velocity impact behavior of doubly curved sandwich panels. The sandwich panels are manufactured using carbon/fiber epoxy composite face sheets, polyurethane foam core and 3D-printed PLA plastic cellular auxetic (re-entrant) honeycombs. High-velocity impact tests are carried out by using a single-stage air gas gun test machine. A spherical steel projectile with the radius of 5 mm is impacted to the center of the specimens with the speed of 100 m/s. The experimental data are used to validate explicit finite element models of the doubly curved structures. An analytical model is also developed for the ballistic limit of the flat and doubly curved sandwich panels, and the analytical results are compared to those obtained from the numerical ones. Parametric numerical analyses of the high-speed impact of the curved sandwich panels are then carried out considering various radii of curvature of the panels. The results show that the energy absorption is increased as the curvature is decreased for the panels with both foam and re-entrant core. In addition, the core configuration provides a key role in the impact resistance of the sandwich panels. Re-entrant models show an increase in specific energy absorption (SEA) compared to the foam core types.

Dynamic fracture behaviour of additively manufactured polymers and composites under ballistic impact

Recent technological advancements led to active research in the field of additive manufacturing (AM) thanks to its ability to fabricate complex structures with reduced material waste. While many studies focused on quasi-static performance of AM materials and structures, investigations on the dynamic performance of these materials are still limited, especially for polymers and composites. The aim of this research is to investigate the dynamic fracture behaviour of AM polymer composites under ballistic impact. Nylon reinforced with short carbon fibres was selected, and fused deposition modelling was used to fabricate solid quasi-isotropic structures. Quasi-static tensile and compression tests were carried out based on ASTM standards to characterise the elastic-plastic properties of the manufactured material. Based on these tests, the material’s deformation and fracture behaviour can be considered elastic-brittle. Further, dynamic mechanical analysis was conducted under a frequency sweep at room temperature to examine the viscoelastic properties; the material exhibited high elastic behaviour. Then, ballistic impact tests were performed on solid plates using a gas gun with 9 mm spherical steel projectiles at velocities ranging from 95 m s-1 to 120 m s-1. Post-experimental observation revealed the complete target perforation, with a circular hole at the front of the plates and delamination at the back. The dynamic experimental conditions were reproduced within the finite-element simulations, employing Hashin damage criteria via a user subroutine. A similar perforation was achieved at the front of the plate.

Penetration dynamics of steel spheres into a ballistic gelatin: Experiments, nondimensional analysis, and finite element modeling

Ballistic gelatin is widely used as a simulant of soft tissues, and its dynamic responses to high-speed projectile penetration are critical for understanding soft tissue damage, wound ballistics, and protection gear design. Here, we investigate penetration dynamics of spherical steel projectiles with different diameters into a ballistic gelatin at different incident velocities. The projectile diameter ranges from 1 mm to 5 mm, and the incident velocity, from 50 m s−1 to 400 m s−1. Penetration dynamics is captured with high-speed photography. A power-law relation is found between the maximum penetration depth and projectile kinetic energy at high incident velocities, but not at intermediate and low velocities. Nondimensional analysis is applied to the penetration depth; a general relation is established for nondimensional maximum penetration depth as a function of projectile density, projectile diameter and projectile incident velocity for low-, intermediate- and high-speed penetration, and this relation can accurately describe the experiments. The drag force of projectile is analyzed to explain the relation between projectile acceleration and velocity. In addition, a calibrated finite element model reproduces well experimental observations such as the maximum penetration depth and projectile trajectory.

Experimental Study of Tensile Preloading Influence on the Mechanical Behaviour of Pseudo-Ductile Hybrid Composite under High-Velocity Impact

The hybridisation of fibre-reinforced plastics is one of the perspective technological methods that make it possible to reduce the sensitivity of polymer composites to stress concentration and increase their damage tolerance. In this case, hybridisation means a combination of different types of reinforcing fibres in one yarn, one layer or one package. In most published papers, the authors investigated the mechanical behaviour of hybrid fibre-reinforced plastic under static loading or low-velocity impact conditions only. At the same time, statically preloaded structures made of composite materials can also be subjected to high-velocity impact. Tensile or compressive preloading affects not only the amount of energy absorbed by the composite but also changes the deformation and fracture pattern. This paper presents the results of the experimental study of the mechanical behaviour of a woven carbon/aramid hybrid composite under tensile preloading and high-velocity impact. Pre-tensioned specimens of homogeneous and hybrid composites were subjected to a high-velocity impact by a steel spherical projectile with the velocities up to 900 m/s. The experimental results showed that the hybrid composite had the lowest sensitivity of the ballistic limit to the tensile preloading.

Experimental Study of Polyurea Protective Coating Effectiveness for Layered Composite Material Reinforced by Glass-Fiber under Impact Loading

One of the promising methods for increasing the resistance of polymer composite materials to high-speed impact is the use of protective shockproof coatings. At the same time, over the past two decades, polyurea have been gaining noticeable popularity among such coatings. This work is devoted to study the effect of polyurea coating of 1.2 mm thickness on ballistic resistance characteristics of glass-fibre reinforced layered polymer of 8.5 mm thickness. During the experiments thirteen composite targets was affected by high-speed impact loading in the range of 80…150 m/s by spherical steel projectile of 23.8 mm diameter. It was shown that using the polyurea coating can increase the ballistic limit by 19% increasing the mass of the target only by 7%. Dynamic strain and displacement fields on the back surface of the target was obtained using digital image correlation method for 81.2 m/s collision process.

Multiple ballistic impacts on 2024-T4 aluminum alloy by spheres: Experiments and modelling

• First investigation on multiple ballistic impacts of 2024Al-T4 alloy. • Crater parameters exhibit power-law increase with the number of impacts. • Twin-like deformation bands and macro-deformation twins coexist around crater walls. • FEM modelling reveals accumulated shear strain leads to deformation twinning. Multiple ballistic impacts are carried out on a 2024-T4 aluminum alloy by spherical steel projectiles (5-mm diameter) at ∼ 400 m s − 1 , to investigate its dynamic deformation and damage. The ballistic impact process is captured with high-speed photography. Postmortem samples are characterized with optical imaging, three-dimensional laser scanning, microhardness testing and electron backscatter diffraction. With increasing number of impacts, crater diameter increases slightly, but crater depth and crater volume increase significantly, and strain accumulation leads to microhardness increase overall. Crater parameters all follow power-law relations with the number of impacts. Twin-like deformation bands and macroscopic deformation twins are produced by impact as a result of spontaneous dislocation self-pinning under high strain rate, large shear deformation. Under multiple impacts, shear strain accumulation in the arc-shaped region of the crater induces deformation twinning when it exceeds a critical value ( ∼ 1.1 − 1.6 ). It is highly possible that the deformation twins are related to deformation bands, since they both share one set of the { 111 } pole with the initial matrix grain. A finite element method model is optimized to reproduce experimental observations and interpret deformation mechanisms.

On the improvement of the ballistic performance of a silicon carbide tile through pre-stress: Experiments and simulations

A pre-stressing technique for improving the ballistic performance of a circular silicon carbide tile has been tested against ø12-mm spherical steel projectile. The confining pre-stress was achieved through a heat-shrunk steel collar and was evaluated through neutron diffraction for the ceramic-collar system. Subsequent ballistic experiments and simulations of the impact event were used to elucidate the mechanisms and benefits of pre-stress on the ballistic response. CT-scans of various specimens, post-impact, show that the pre-stress affects the trajectory of the Hertzian cone and limits the overall damage. Furthermore, simulations qualitatively agreed with the experimental result, showing a reduction in crack propagation and altered paths of damage. Greater confining stress led to higher negative triaxiality, which act to arrest the tensile hoop stresses and corresponding cracks.