High-velocity Projectile Impact Research Articles

ULTRA-HIGH-PERFORMANCE FIBRE-REINFORCED CONCRETE UNDER HIGH-VELOCITY PROJECTILE IMPACT - PART 2. APPLICABILITY OF PREDICTION MODELS

Semi-infinite targets of Ultra-High-Performance Fibre-Reinforced Concrete with various fibre volume fractions were subjected to the high-velocity projectile impact using in-service bullets. In this study, a variety of empirical and semi-analytical models for prediction of the depth of penetration and mass ejection were evaluated with respect to the experimental results. Models for the depth of penetration and spalling mass ejection were revisited and applied both with deformable and nondeformable projectiles parameters. The applicability of the prediction models was assessed through a statistical comparison of values from models with experimental results. The evaluation of the applicability was made through the newly proposed measure of a relative prediction accuracy for model selection and model estimation, which was verified with established statistical accuracy evaluations, such as accuracy ratio, logarithmic standard deviation and correlation coefficient. The best fit to the experimental readings was provided by newer semi-analytical models, which are incorporating additional concrete parameters beside compressive strength while the majority of older models failed to provide sufficient accuracy.

Ceramic balls protected ultra-high performance concrete structure against projectile impact–A numerical study

Ceramic materials have excellent mechanical properties such as light weight, great hardness and high compressive strength. In this paper, a numerical study is conducted to investigate the response of ceramic balls protected ultra-high performance concrete (UHPC) targets against the high-velocity rigid projectile impact using the coupled smoothed particle hydrodynamics-finite element (SPH-FE) method in LS-DYNA. Based on the validated numerical models, parametric studies are performed to explore the effect of diameter, spatial arrangement and material type of ceramic balls as well as the impact position on the dynamic performance of UHPC targets, and then perforation and ballistic limits of ceramic balls protected UHPC targets are obtained. Compared with other UHPC slabs at the striking velocities from 500 m/s to 850 m/s, UHPC slabs protected with 6-layer hex-pack arranged ceramic balls with the diameter of 20 mm is most effective in terms of reducing the depth of penetration (DOP). In addition, the utilization of ceramic balls is economical in protective structures since the damaged ceramic balls can be replaced and undamaged ceramic balls are reusable.

Fiber-Reinforcing Effects on Damage of Reinforced Mortar Columns under High-Velocity Impact of Projectile

Fiber-Reinforcing Effects on Damage of Reinforced Mortar Columns under High-Velocity Impact of Projectile

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.

Investigating the resistance of reinforced barriers to high velocity projectiles

The resistance of concrete barriers to high velocity projectile impact from firearms is a research topic that has been of interest for quite some time, with the first known study going back to the mid-18th century. Despite this long history, only a very limited number of the test results are available in the public domain due to their sensitive nature and strategic importance. This situation has made the development of precise models for predicting the effects of ballistic impact difficult, despite the recent availability of highly refined and powerful calculation tools. Many researchers are still convinced that a validated methodology does not currently exist for this type of problem due to the number of uncertainties. Within this context, the objective of the present work is to study projectile impact on barriers made of reinforced concrete with explicit Finite Element (FE) simulations. In particular, this paper presents a FE analysis that considers the full range of projectile class as defined in the ballistic standards. Results from simulation are also compared with experiments.

Analytical models for the perforation of thick and thin thickness woven-laminates subjected to high-velocity impact

Abstract This paper deals with the problem of high-velocity impact of a low-mass projectile on woven composite plates. A nondimensional formulation of two analytical models has been developed (one for thin laminates and the other for thick ones). Both analytical models are based on energy conservation and have been applied for the ballistic impact on E-glass woven fibres/polyester composite plates. The results of the models (mainly the ballistic limits) have been compared with experimental results. The value of the ratio target thickness/projectile diameter determining whether the laminate behaves as thick or thin has been established.

High-velocity projectile impact induced 9R phase in ultrafine-grained aluminium

Aluminium typically deforms via full dislocations due to its high stacking fault energy. Twinning in aluminium, although difficult, may occur at low temperature and high strain rate. However, the 9R phase rarely occurs in aluminium simply because of its giant stacking fault energy. Here, by using a laser-induced projectile impact testing technique, we discover a deformation-induced 9R phase with tens of nm in width in ultrafine-grained aluminium with an average grain size of 140 nm, as confirmed by extensive post-impact microscopy analyses. The stability of the 9R phase is related to the existence of sessile Frank loops. Molecular dynamics simulations reveal the formation mechanisms of the 9R phase in aluminium. This study sheds lights on a deformation mechanism in metals with high stacking fault energies.

The influence of rubber layer on the response of fluid-filled container due to high-velocity impact

When hit by a high-velocity projectile, a fluid-filled container might suffer from Hydrodynamic Ram. The entire tank structure can possibly rupture due to the loads from primary shock wave and a cavity developed in the liquid. In this paper, a countermeasure, of which the rubber layer is inserted on the walls of the tank, is proposed to alleviate the dynamic response of fluid-filled container under the impact of high-velocity projectile. The applicability of the numerical method in simulating the process of high speed projectile penetrates the fluid-filled container is validated by comparing the numerical results with the experimental data in the literature. Then, numerical simulations were conducted to investigate the process of projectile penetrates the fluid-filled container with rubber layer insertion between the walls of container and fluid, with the velocities of 450m/s, 600m/s, 750m/s, 900m/s and 1050m/s, respectively. The influence of rubber layer on the dynamic responses of tank walls, the change of pressure of shock wave in water and the energy absorption of structural walls and rubber layers were analyzed. The results indicate that the rubber layer has a significant effect on shock wave acting on container walls. The dynamic response of liquid tank under the loading of the shock wave and local pressure, which is caused by the high speed fragments traveling in the fluid, decreases remarkably.

Mechanical and morphological study of polymer composite plates having different fiber surface treatments with particular response to high velocity projectile impact

This study investigates morphological and mechanical behaviors of polymer composite plates reinforced with surface modified glass fiber woven roving with special interest in high velocity impact response. Four types of surface modification were applied to the glass fiber surface, namely: virgin fabric (silane coupling agent removed), silane-treated (as received fabric), corona-treated virgin fabric and silane- plus corona-treated fabric. Hand layup technique was adopted to make composite plates with [0/90, ±452, 0/90] layup using unsaturated polyester resin as matrix. Mechanical testing methods, such as tensile and bending loading as well as low velocity Izod impact and high velocity impact tests in velocities of 88.5, 108.3 and 144 m/s were conducted. The results showed that, although in lower part of high velocity impact rates, i.e., 88.5 m/s, the panels with fiber fabric treatment of silane plus corona revealed significant increase in ballistic resistance, but in general, it was found that the order of optimum performance for E-glass fiber woven roving surface modification methods are: silane, silane plus corona treatment, virgin fabric and sole corona treatment, respectively. The results further revealed that at impact velocities of 108.3 and 144 m/s, the energy absorptions for the samples with silane treatment are 7.9 and 6.6% higher compared to the samples with silane plus corona discharge treatment (S + C) samples, respectively. Damage assessment revealed higher damage extension in the samples with fiber having silane plus corona discharge treatment. Morphological studies on surface roughness were conducted by SEM analysis. The results correlated well with mechanical and impact results in those samples with higher surface roughness showed better mechanical performance and that silane treatment was the dominant factor in performance.

A Damaged Constitutive Model for Rock under Dynamic and High Stress State

The main research work of this paper focuses on the theoretical prediction of the constitutive relationship for rock, concrete, and other quasi-brittle materials under dynamic and complex stress state and the influence of dynamic mechanical behavior of rock on practical engineering problems was studied. A damaged elastoplastic model (DEPM) is established for the investigation and prediction of static or dynamic mechanical behavior of rock material. The mechanical behavior (brittleness or plasticity) and dynamic response (due to underground impact pressure and high-velocity impact of projectile) of rock under high in situ stress were investigated via the DEPM combined with the explicit finite element method. This paper suggests the influence of the brittle or plastic mechanical behavior of rock material on deep underground rock engineering.

Modeling and Simulation of High-Velocity Projectile Impact on Storage Tank

A series of numerical modeling and simulations were conducted for dynamic responses of a fluid-filled storage tank subjected to impact loading resulting from a high-velocity projectile. The focus of the study was placed on two phases. The first phase examined the structural response during the impact period without penetration while the second phase investigated the period of a projectile traveling through a fluid medium inside the storage tank. Some parametric studies were conducted to understand the dynamic responses of the structure. The parameters considered were the fluid filling level in the storage tank, fluid density, tank material properties, and projectile mass and velocity. Understanding what parameters would result in most severe damage to the structure can lead to improved design of storage tanks and proper protection against any potential incident.

Resistance of high-performance fiber-reinforced cement composites against high-velocity projectile impact

This paper presents experimental and numerical studies on the performance of seven high-performance fiber-reinforced cement-based composites against high velocity projectile impact (HVPI). The materials investigated involved four fiber-reinforced high-strength concretes (FRHSCs) with 28-day compressive strengths ranging from about 60 to 140 MPa, two strain hardening cement-based composites (SHCCs), and a fiber-reinforced high-strength mortar (FRHSM). Of the two SHCCs, one was reinforced with 0.5% steel fibers plus 1.5% polyethylene (PE) fibers by volume of the composites, whereas the other was reinforced with 2% of polyvinyl alcohol (PVA) fibers. The other composites were reinforced with 0.5% of steel fibers. Ogive-nose shaped projectiles, with a diameter of 28 mm and weight of about 250 g, were used for the HVPI tests at projectile velocities of ~400 and ~600 m/s. The localized damage, particularly the penetration depth, was examined and discussed. Results indicate that the higher compressive strength and greater toughness of cement-based composites, as well as the presence of strong coarse aggregate and fibers, contribute positively to the impact resistance of composites. In addition, it was found that the penetration depth of the composites subjected to HVPI is reduced with an increase in the elastic modulus, as well as with the “effective hardness index” calculated based on the hardness and proportion of the coarse aggregate and mortar matrix. Numerical studies were conducted to simulate the localized damage of the FRHSCs and SHCCs due to the HVPI using the finite element software LS-DYNA. The numerical models adapted predict the penetration depth well. The numerical simulation results indicate that it takes a longer time to stop the projectile traveling at the same initial velocity in the SHCC specimen than in the FRHSC specimen due to the absence of hard and strong coarse aggregate in the former.

Honeycomb sandwich panels subjected to combined shock and projectile impact

Structural response and failure modes of honeycomb sandwich panels subjected to a shock (impulsive pressure) followed by a high velocity projectile impact were investigated using detailed finite element simulations. Performance of sandwich panels was quantified by maximum transverse deflection of the bottom face sheet and core crushing strain along with an investigation of their optimal behavior. Three failure modes were observed in panels – core failure, top face failure, and tearing and detachment from support. Failure maps of honeycomb sandwich panels were constructed to show the failure mode of panels as a function of shock intensity, projectile velocity and panel core relative density. In addition, a limited set of simulations were carried out to study the role of incident angle of projectile on the overall performance of a panel. These simulations showed that maximum deflection occurred for vertically impacting projectiles. However, we found that this did not directly translate to maximum core crushing strain in sandwich panels. The results provide new insight into the performance and failure of sandwich panels under complex dynamic loading conditions, and further highlight the potential of these panels for development of threat-resistant structural systems.

Energy absorption capacity of a sustainable Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) in quasi-static mode and under high velocity projectile impact

This paper investigates the energy absorption capacity of a sustainable Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) in quasi-static mode and under high velocity projectile impact. The design of the sustainable concrete mixtures aims on achieving a densely compacted cementitious matrix with a relatively low binder amount, employing the modified Andreasen & Andersen particle packing model. The experiments on UHPFRC are performed using a 4-point bending test and high velocity projectile impact tests. The obtained results show that although the utilization of hybrid steel fibre enhances the mechanical properties of the developed UHPFRC, the application of fibres with hooked ends is crucial in improving the energy absorption capacity of the sustainable UHPFRC in quasi-static mode. However, under high velocity projectile impact, the UHPFRC mixture with hybrid fibres shows a much better energy absorption capacity than the one with hooked steel fibres only, particularly in resisting the scabbing at the rear surface. The intrinsic mechanisms for the energy absorption capacity of the sustainable UHPFRC in quasi-static mode and under high velocity projectile impact are studied and analysed.

Analytical modeling for perforation of foam-composite sandwich panels under high-velocity impact

In this paper, a new simple analytical model for perforation process of composite sandwich panels subjected to high-velocity impact of flat-ended projectile is presented. The panels consist of foam core sandwiched between two composite skins. In the analytical model, global deformation, plug shearing or localized tensile fracture, delamination of front and back-up composite skins, and the absorbed energy during the perforation of the sandwich panel are calculated considering the local indentation and also the energy balancing equation is employed to determine the ballistic limit and residual velocity of projectile. The results of current new model are compared with the experimental results available in the open literature and the finite element simulation results obtained by the LS-Dyna code. A good agreement is observed between the analytical and numerical model results and the experimental results.

A comparison of finite element analysis to smooth particle hydrodynamics for application to projectile impact on cementitious material

The response of structural components of high-strength cementitious (HSC) materials to projectile impact is characterized by high-rate fragmentation resulting from strong compressive shock waves coupled with reflected tensile waves. Accurate modeling of armor panels of such brittle materials under high-velocity projectile impact is a complex problem requiring meticulous experimental characterization of material properties. In a recent paper by the authors, an approach to handle such problems based on a modified Advanced Fundamental Concrete (AFC) constitutive model was developed. In the HSC panels considered in this study, an analogous approach is applied, and the predictions are verified with ballistic impact test data. Traditional Lagrangian finite element analysis (FEA) of these problems tends to introduce errors and suffers from convergence issues resulting from large deformations at free surfaces. Also, FEA cannot properly account for the issues of secondary impact of spalled fragments when multiple armor panels are used. Smoothed particle hydrodynamics (SPH) is considered to be an attractive alternative to resolve these and other issues. However, SPH-based quantitative results have been found to be less accurate than the FEA-based ones when the deformations are not sufficiently large. This paper primarily focuses on a comparison of FEA and SPH models to predict high-velocity projectile impact on single and stacked HSC panels. Results are compared to recent ballistic experiments performed as a part of this research, and conclusions are drawn based on the findings.

Polymer based aerospace structures under high velocity impact applications; experimental, constitutive and finite element analysis

Polymethyl methacrylate (PMMA) and Polycarbonate (PC) are two famous optically clear thermoplastic polymers widely used in various aeronautical and astronatucial applications. Owing to their exceptional transparency, process shape adaptability, low density and high impact strength they find particular attention in aerospace industry where they are used to manufacture air craft canopies, windshields, impact resistant windows, visors and safety glasses. The design and manufacturing of the satisfied polymeric structures involve accurate modeling of the material behavior and detailed analysis of their service behavior under extreme loading conditions. In order to evaluate the material behavior under these loading conditions, extensive work in terms of experimental characterization and material constitutive modeling is required. A systematic research methodology including the material characterization, material constitutive modeling, constitutive model implementing and finite element prediction of mechanical behaviors is proposed in this work. The material characterization tests were performed by means of universal testing machine and Split Hopkinson pressure bar (SHPB) setup. On the basis of performed tests and using phenomenological approach, a constitutive model was proposed to successfully predict the entire deformation behavior of polymers under various loading conditions with sufficient accuracy. The model was implemented numerically by establishing a User-defined material subroutine (UMAT) in explicit Finite element (FE) solver LS-DYNA. The model successfully ascertained the dynamic behavior of PMMA based aircraft windshield and PC based astronaut helmet visor under application of high velocity projectile impact. A number of FE simulations were carried out to determine the critical impact energy, maximum deformation and stress level in these structures. The simulations results help to evaluate various design approaches to optimize the structural response prior to preliminary experimentations and therefore provide an alternative to costly and time consuming extensive experimental tests.

구형 비상체에 의한 충격하중을 받는 강섬유보강 콘크리트 패널의 손상특성

This paper investigates the effects of fiber volume fraction and panel thickness on face damage characteristics of steel fiber-reinforced concrete (SFRC) under high-velocity globular projectile impact. The target specimens were prepared with 200 × 200 mm prismatic panels with thickness of 30 or 50 mm. All panels were subjected to the impact of a steel projectile with a diameter of 20 mm and velocity of 350 m/s. Specifically, this paper explores the correlation between mechanical properties and face damage characteristics of SFRC panels with different fiber volume fraction and panel thickness. The mechanical properties of SFRC considered in this study included compressive strength, modulus of rupture, and toughness. Test results indicated that the addition of steel fiber significantly improve the impact resistance of conventional concrete panel. The front face damage of SFRC panels decreased with increasing the compressive toughness and rear face damage decreased as the modulus of rupture and flexural toughness increased. To evaluate the damage response of SFRC panels under high-velocity impact, finite element analysis conducted using ABAQUS/Explicit commercial program. The predicted face damage of SFRC panels based on simulation shows well agreement with the experimental result in similar failure mode.

3D finite element simulations of high velocity projectile impact

An explicit three-dimensional (3D) finite element (FE) code is developed for the simulation of high velocity impact and fragmentation events. The rate sensitive microplane material model, which accounts for large deformations and rate effects, is used as a constitutive law. In the code large deformation frictional contact is treated by forward incremental Lagrange multiplier method. To handle highly distorted and damaged elements the approach based on the element deletion is employed. The code is then used in 3D FE simulations of high velocity projectile impact. The results of the numerical simulations are evaluated and compared with experimental results. It is shown that it realistically predicts failure mode and exit velocities for different geometries of plain concrete slab. Moreover, the importance of some relevant parameters, such as contact friction, rate sensitivity, bulk viscosity and deletion criteria are addressed.

Analytical and numerical investigation of polyurea layered aluminium plates subjected to high velocity projectile impact

This paper discusses on the penetration of high velocity projectiles through aluminium–polyurea composite layered plate systems. An analytical model has been proposed to predict the residual velocity of aluminium–polyurea composite plates, and validated with both experimental and numerical investigations. Full metal jacket (FMJ) projectiles (5.56mm×45mm), corresponding to NATO standard SS109, were fired at the aluminium–polyurea composite layered plate systems from a distance of 10.0m at a fixed velocity of 945m/s. Four different composite plate configurations were used with thicknesses varying from 16 to 34mm. Each configuration consisted of six specimens. Residual velocities for each individual test were recorded. Numerical simulations of the penetration process have been performed using advanced finite element code LS-DYNA®. The well-established Johnson–Cook and Mooney–Rivlin material models were used to represent the stress–strain behaviour of aluminium and polyurea in the numerical analysis. The analytical and numerical models provided good approximations for the residual velocities measured during the experimental tests. Polyurea layers contributed positively towards the reduction of residual velocity of the projectile in composite plate systems. In addition, ballistic limit curves for different composite systems have been established based on the validated models. As the results showed that polyurea contributes positively towards the reduction of residual velocity of projectiles, the findings of this study can be effectively used for the similar applications in future armour industry.