Projectile Nose Research Articles

Influence of metal layer distribution on the projectiles impact response of glass fiber reinforced aluminum laminates

The effect of the distribution of aluminum layer through the thickness of fiber metal laminates (FMLs) on their projectiles impact response is studied using high speed 3D digital image correlation technique (DIC). The FMLs consisting of aluminum alloy 2024-T3 sheets of thicknesses 0.3 mm, 0.4 mm, and 0.6 mm and glass fiber reinforced epoxy layers (two layers with each of 0° and 90°) were prepared by the hand layup process followed by vacuum bagging. The metallic layers are placed at different locations through the thickness of four different layups while keeping the total metal layer thickness constant. The hemispherical and conical nose projectiles of the same mass are impacted normal to the FMLs plate using nitrogen gas gun. The performance of the FMLs is evaluated using different parameters such as the deformation history, residual deformation and also the surface and internal damages. FML 4/3–0.3 in which the two adjacent composite layers with different fiber orientations separating by an aluminum layer exhibited the highest deformation with hemispherical projectile impact for the same impact energy level. The deformation was found to be lower and nearly same for the other three FMLs. This observation is also noticed in the case of drop weight impact (low velocity impact). The FML 2/1–0.6 in which the composite layers were stacked together exhibited a comparatively higher lateral spread of delamination and interlayer opening with hemispherical projectile impact when compared to FML 4/3–0.3, indicating that the lateral spread of damage within the FML can be decreased by distributing the aluminum layers in the FML. This is also observed in the case of drop weight impact.

Modeling on mass loss and nose blunting of high-speed penetrator into concrete target

Mass loss and nose blunting of the projectile are often observed in high-speed penetration into concrete target. A new theoretical model is established to present the process of mass abrasion of projectile during penetration and to predict the mass loss and nose shape of the residual projectile after penetration. In order to better describe the effect of aggregate on the mass abrasion of penetrator, both the aggregate volume fraction and its shear strength are introduced into the present model. In the present model, the caliber-radius-head value of projectile nose is a key parameter and the mass loss and nose shape of projectile can be obtained easily only by solving a differential equation for the caliber-radius-head value and the penetrating velocity v, which is much more convenient than the incremental calculation and all other methods of mass receding of projectile outer surface. The calculation results show a good agreement with experimental results. According to the present model of mass abrasion, the depth of penetration of projectile and its acceleration curve during penetration are further calculated by considering the effects of mass loss and nose blunting of projectile.

Ballistic performance evaluation of polycarbonate plate based on quasi-static perforation

The present work deals with the experimental investigation involving Quasi-static perforation of thin circular polycarbonate plate for ballistic performance evaluation. Effective diameter and thickness of polycarbonate plate is 205 mm and 2.66 mm respectively. Quasi-static perforation is performed on Servo-mechanical universal testing machine of capacity 50 kN using Blunt and Truncated cone penetrators of diameter 12.8 mm made of EN31 alloy steel. The velocity of the penetrator (indenter) is set at 2 mm/min and the impact is carried out at the centre of the plate. The results obtained based on Quasi-static tests are used in conjunction with the impact test performed using pneumatic gun set-up [1] for the same set of target plate and projectile nose shape. The ratio of the dynamic and quasi-static perforation energy defined as dynamic enhancement factor has been calculated. The variation of dynamic enhancement factor (DEF) with the impact velocity exhibit a linearly increasing pattern similar to those in literature for metallic plates [2].

Minimum drag and heating 0.3-caliber projectile nose geometry

Understanding the performance of penetrators and aerodynamic bodies of revolution (missiles, rockets, aircraft noses, etc.) requires a close look at the drag and the heat transfer characteristics at a wide range of supersonic flight conditions. This research utilizes computational study and compares the aerothermal loads of supersonic flows around a new penetrator geometry, derived based on the optimization of the nose factor, to those of other common projectile shapes: conical, tangent-ogive, and power series nose geometries. The abundance of research on 0.3-caliber projectile made the choice for this research simple in order to maximize our ability to compare to the existing data. The comparison of our 0.3 caliber cylindrical projectile with other geometries shows that within the range of 500–1500 m/s flight speed the new geometry has the lowest aerodynamic drag, lowest body temperature, and least amount of heating.

Experimental investigation on dynamic failure of water-filled vessel subjected to projectile impact

In this investigation, a series of experiments are performed to study the deformation and failure of fluid-filled vessel subjected to high speed impact loading. The water-filled vessel with aluminum alloy target panels were impacted by the projectiles at the initial velocities of 100–300 m/s. Three different kinds of projectiles were considered to investigate the influence of nose shape of projectile on the failure modes of the water-filled tank. The high-speed photography was used to record the process of the projectile moving and the formation of cavity in water. The strain histories of target panels were measured by using the strain gauges. The results indicate that the hydrodynamic ram effect in the water-filled tank increased the damage of the target panels. The deformation of panels increased with the projectile nose coefficient (caliber-radius-head, CRH) increasing. The deformation and failure of the rear panel were more serious than those of the front panel. Additionally, the typical failure modes of the panels could be subdivided into three modes. The relationship between the kinetic energy and CRH value of the projectiles and the deformation of the panels was established.

A Numerical Investigation on Oblique Projectile Impact Behavior of AA5083-H116 Plates

In this paper, oblique impact of ogive nose projectile on 5083-H116 aluminum alloy plates was numerically investigated. Three parameters such as impact velocity, impact angle and target configuration were varied to observe their influence on the ballistic resistance of targets. Based on the results, the oblique angle of impact acts an important role on the deformation mode of targets. The penetration of projectile dominates targets under low oblique angle impacts and the deformation changes from embedment to ricochet as oblique angle increases. Beside the oblique angle, the ballistic resistance of target is heavily dependent on impact velocity. Targets are perforated as impact velocity increases even if oblique angle becomes larger. Target configuration is another factor on the protective performance which is increased using thicker plates. The ballistic response of monolithic and double layer targets for the same thickness is very close each other.

Strain Behavior of Concrete Panels Subjected to Different Nose Shapes of Projectile Impact.

This study evaluates the fracture properties and rear-face strain distribution of nonreinforced and hooked steel fiber-reinforced concrete panels penetrated by projectiles of three different nose shapes: sharp, hemispherical, and flat. The sharp projectile nose resulted in a deeper penetration because of the concentration of the impact force. Conversely, the flat projectile nose resulted in shallower penetrations. The penetration based on different projectile nose shapes is directly related to the impact force transmitted to the rear face. Scabbing can be more accurately predicted by the tensile strain on the rear face of concrete due to the projectile nose shape. The tensile strain on the rear face of the concrete was reduced by the hooked steel fiber reinforcement because the hooked steel fiber absorbed some of the impact stress transmitted to the rear face of the concrete. Consequently, the strain behavior on the rear face of concrete according to the projectile nose shape was confirmed.

Investigation and comparison of performance of some air gun projectiles with nose shape modifications

Shooting accuracy of air gun projectiles is very important in sport tournaments and has always been questioned by enthusiasts. For this purpose, the performance of four samples of air gun projectiles (pellets) with various shapes and calibers of 4.5, 5.5 and 6.35 mm was studied in this article. The projectiles were four basic shapes: flat nose, sharp nose, round nose and spherical. After these projectiles were modeled geometrically, the three-dimensional compressible turbulent Navier–Stokes equations and dynamic equations of the projectiles’ motion were solved in a coupled form and in a moving computational grid. The computed results describe the trajectory, velocity variations and the altitude loss of the projectiles with time and location. Comparisons indicate that the round nose projectile had the best performance at long distances compared to the other samples. The flat nose projectile exhibited great performance at short distances, but behaved weakly at long distances. In addition, the effect of nose shape on the performance of the sharp and round nose projectiles was studied and the optimum nose shapes were identified.

Experimental study of ballistic resistance of sandwich targets with aluminum face-sheet and graded foam core

In this research, we have investigated the ballistic resistance of sandwich structures with aluminum face-sheet and graded polyurethane foam core with different densities. The effects of graded changes of core foam density and the effect of the sequence of foam layers with different densities on energy absorption and ballistic limit of sandwich structures under the impact of hemispherical nose projectiles at high speeds (160 to 300 m/s) are studied. The results of this study showed that increasing the density and thickness of the foam core leads to increase in the ballistic limit and energy absorption; also, the ballistic limit of sandwich structures with the same mass with graded foam core for three- and five-layer panels is, respectively, 10.37 and 5.57% more than single-layer foam core with the average density in case the foam layer with less density is placed in the impact side. By using the graded foam core (laminate), the core resistance is increased and the damaged zone shape is changed, and the energy absorption of back face-sheet is increased.

An experimental investigation into the high velocity penetration resistance of CFRP and CFRP/aluminium laminates

Carbon fibre-reinforced composite materials are of high potential as protective casing in the aerospace area, acting as an effective solution to lighten components against the collision. The high velocity penetration resistance abilities of unidirectional CFRP laminates and two carbon fibre reinforced aluminium laminates CRALL2/1 and CRALL3/2 (fabricated from T700S CFRP layers combined with aluminium alloy 2024-T3 layers) were evaluated by the ballistic tests with a flat, hemispherical or conical nosed projectile. Revealed from ballistic tests that fracture modes, ballistic limits and specific energy absorptions of CRALLs and CFRP were sensitive to nose shapes. Higher ballistic limits and specific energy absorption ability were performed by CRALLs than monolithic CFRP impacted by all shapes due to the strain rate hardening effect and failure conversion effect. In particular situation of flat nose projectiles penetrating, the specific energy absorption of the CRALL3/2 was 8% higher than that of monolithic aluminium alloy 2024-T3 at same thickness. The CRALLs may then be designed as effective lightweight structures to protect frames against collision in the aerospace area and outperform the traditional single CFRP laminates.

Perforation mechanics of 2024 aluminium protective plates subjected to impact by different nose shapes of projectiles

This paper focuses on the mechanical behaviour of aluminium alloy 2024-T351 under impact loading. This study has been carried out combining experimental and numerical techniques. Firstly, experimental impact tests were conducted on plates of 4mm of thickness covering impact velocities from 50m/s to 200m/s and varying the stress state through the projectile nose shape: conical, hemispherical and blunt. The mechanisms behind the perforation process were studied depending on the projectile configuration used by analyzing the associated failure modes and post-mortem deflection. Secondly, a numerical study of the mechanical behaviour of aluminium alloy 2024-T351 under impact loading was conducted. To this end, a three-dimensional model was developed in the finite element solver ABAQUS/Explicit. This model combines Lagrangian elements with Smoothed Particle Hydrodynamics (SPH) elements. A good correlation was obtained between numerical and experimental results in terms of residual and ballistic limit velocities.

High velocity impact response of carbon nanotubes-reinforced composite sandwich panels

Effect of adding carboxyl-modified multi-walled carbon nanotubes (COOH-MWCNTs) on the high velocity impact of sandwich panels with plywood core and two different facesheets, E-glass/epoxy and E-glass/ nylon 6, was investigated in this study. Facesheets were prepared with and without COOH-MWCNTs. Three different weight percentages of 0.3, 0.5, and 1 wt% of COOH-MWCNTs were used to reinforce epoxy and nylon 6 polymers. The sandwich panels’ estimated ballistic limit ( Vbl) and impact energy absorbed ( Eab) were determined by subjecting them to impact velocities in their ballistic limit range and above by conical nose projectile. It was found that the sandwich panels containing E-glass/ epoxy facesheets exhibited more energy absorption than those containing E-glass/nylon 6 facesheets. Moreover, the high velocity impact response of sandwich panels improved with the increase of COOH-MWCNT content. Besides, the damage area for different types of materials studied is presented, and it is observed that at a given impact velocity, the damage size on the rear facesheet of target around the point of impact decreases on addition of COOH-MWCNTs.

Reprint of: A new simplified analytical model for soil penetration analysis of rigid projectiles using the Riemann problem solution

A new simplified analytical model to analyze the penetration of rigid projectiles into soil media is presented. The soil medium is represented by a set of discs, responding in the radial direction under plain strain conditions. A convenient mathematical formulation is derived based on some simplifying assumptions. According to the present approach, the contact parameters in each disc are computed using the developed exact solution of the symmetrical Riemann problem for an irreversible compressible medium. One of the new features of the present model is the incorporation of the exact nonlinear equation of state including unloading-reloading thus considering another key variable that is the maximum medium density that is attained in the process of active loading before unloading is started. Thus the new model considers unloading in the soil medium during the progress of penetration. The present model focuses on the projectile motion and provides information on its velocity, deceleration and depth time histories. It also provides information on the interaction of the projectile with the surrounding soil such as the normal stress distribution along the projectile nose and is capable of determining the contact zone between the nose and the soil. Comparison of the present model results with two-dimensional numerical results as well as with different analytical models and with experimental data is performed. The present model predictions are found to be in good agreement with test data and superior to many existing simplified models. Contrary to many other simplified models, the present model is purely theoretical and does not require any empirical constants or special arbitrary assumptions for calculation of the contact pressures along the projectile nose at all times. The calculations require very small computer time and provide much information regarding the projectile motion in the soil medium.

Studying Normal and Oblique Perforation of Steel Plates with SPH Simulations

Axisymmetric and three-dimensional smoothed particle hydrodynamics (SPH) models are developed to simulate normal and oblique perforation of 12 mm-thick Weldox 460 E steel plates. In the models, a particle-to-particle contact algorithm including friction effect is employed to model interactions between projectile and target plate. A constitutive model coupling viscoplasticity and ductile damage is implemented to describe material behaviors of target plate. Both axisymmetric and three-dimensional SPH models are validated by existing experimental results. By using axisymmetric models, effects of projectile structure on normal perforation are systematically studied. Two factors of projectile structure, nose shape and aspect ratio, are considered. Residual velocities, ballistic limits and failure modes are obtained for different projectile nose shapes and aspect ratios. Effects of nose shape and aspect ratio on ballistic limits predicted by SPH simulations are compared with those obtained by an analytical equation. By using three-dimensional models, oblique perforation is simulated. Effects of oblique angle on impact processes are analyzed. Intervals of critical oblique angle of ricochet are obtained for different impact velocities and caliber-radius-head values of ogival projectile. The results obtained in this work can provide reference for the design of protective structures with steels and similar materials. The SPH with contact algorithm including friction effect is proved to be a very effective method for ballistic impact simulation.

Energy absorption in thin metallic targets subjected to oblique projectile impact: A numerical study

The present study investigates the ballistic performance and energy absorption in plastic deformation due to work done in radial, circumferential, axial and tangential directions in 1mm thick aluminum 1100-H12 targets. The targets were impacted by single nosed; ogival, blunt and double nosed; ogival-blunt and blunt-blunt, EN-24 Steel projectiles at 0°, 15°, 30° and 45° oblique incidence angles. Three-dimensional models of both projectiles and the targets were created and numerical analyses were performed in Abaqus Explicit solver. Ballistic performance, mode of failure and energy absorption in the target were compared within the configurations. Targets impacted with double nosed projectiles exhibited higher ballistic limit, followed by single nosed blunt and then by ogive nosed projectile. Single nosed ogive projectiles, showed increase in ballistic limit with the obliquity, whereas blunt, ogival-blunt and blunt-blunt projectiles displayed opposite behavior. The energy absorption in targets subjected to ogival-blunt projectile was found to be highest, followed by targets subjected to blunt-blunt projectile, then single nosed blunt and ogive projectile in the last. Further, total energy absorption in the targets subjected to ogive nosed projectile was increased with the obliquity, whereas, in case of blunt and double nosed projectiles, the energy dissipation was reduced.

Rigid projectile penetration into a concrete medium: A new model

A new simplified model to analyze the penetration of a rigid projectile into a concrete thick medium is presented. The concrete medium is modeled by a set of discs, responding in the radial direction under plain strain conditions. A convenient mathematical formulation is derived based on some simplifying assumptions. A major new feature of the present model is that it hybridizes two different analytical and numerical approaches that have been developed by the authors. In the present model, the Riemann problem exact solution is applied to the interaction of the projectile nose tip with the target. It is assumed that when the nose tip meets a new undisturbed disc, loading occurs during its interaction with the concrete, and therefore the unloading branch of the equation of state is not required in the Riemann problem. The other discs that maintain contact with the projectile nose and had been loaded in earlier time steps undergo unloading, and a special approach has been developed to compute their contact stresses. This entirely new formulation has not been proposed earlier. The present model enables calculations of the projectile motion time history (i.e. deceleration, velocity, and depth). Comparison of the present model results with experimental data shows very good agreement. Contrary to many other simplified models, the present approach does not require any empirical constants or any preliminary assumptions concerning the contact pressures acting on the penetrating projectile nose, as other models do. Computer time of less than 1 min is needed for a complete analysis.

Hemispherical nosed steel projectile high-speed penetration into aluminum target

Terminal ballistic performance of high-strength projectiles penetrating into metallic targets is mostly concerned by both weapon and armor designers. Most existing works are concentrated on the rigid-eroding penetration regime, and limited studies have addressed the rigid-deforming-eroding penetration regime. In this paper, nineteen shots of hemispherical nosed D6A steel projectiles penetration test on 5A06-H112 aluminum targets is conducted with a wide range of velocities (696m/s–1870m/s). The non-monotonic dependence of depth of penetration (DOP) on the impact velocity is observed, which successively corresponds to the three penetration stages, i.e., rigid projectile penetration, deforming projectile penetration without eroding and eroding projectile penetration. Then, for the non-monotonic rigid-deforming-eroding projectile penetration regime, the applicability of the existing six classical theoretical models for both rigid and eroding projectile penetrations is evaluated. Furthermore, the transition velocities (the upper limit of rigid penetration and the lower limit of eroding penetration) are discussed and an empirical judgement criterion for the occurrence of non-monotonic dependence is proposed. Finally, by conducting the dynamic compression test, quasi-static tension test under varying temperature, etc., the Johnson-Cook model parameters for the present target and projectile are calibrated and validated by numerically simulating the present test.

Characteristics of velocity attenuation and cavity expansion induced by horizontal water-entry of truncated-ogive nosed projectiles

In this paper, the horizontal water-entry experiments of truncated-ogive projectiles at the velocity range of 100~150 m/s were conducted using a light-gas gun and a high-speed camera to record the whole water-entry process. The characteristics of the velocity attenuation and the drag coefficients of truncated-ogive projectiles were obtained, and the trajectory stability and the characteristics of velocity attenuation for the flat-nosed, the ogive-nosed and the truncated ogive-nosed projectiles were compared and analyzed. The cavity expanding behaviors induced by the truncated ogive-nosed projectile's water entry were studied and a theoretical model of the cavity expansion was established. The relationships between the radial cavity radius, cavity wall velocity and time, penetration distance at fixed locations and fixed times were obtained, and good agreements were found between the experimental observations and the theoretical analysis.

Ballistic resistance and energy absorption of honeycomb structures filled with reactive powder concrete prisms

Two kinds of innovative re-entrant and hexagonal cell honeycomb sandwich structures filled with reactive powder concrete were proposed, and the ballistic resistance and energy absorption of the sandwich structures were investigated by numerical simulations. The deformation and failure modes of the different structures were analyzed and evaluated in detail. The honeycomb sandwich structures filled with reactive powder concrete prisms improved the capacity of ballistic resistance and energy absorption significantly, compared to the normal reactive powder concrete plates and sandwich structures without reactive powder concrete prisms. The analysis shows that the auxetic re-entrant cell honeycomb sandwich structures have a better ballistic performance than the hexagonal cell honeycomb sandwich structures. The sandwich structures were subjected to impact by three kinds of projectiles: flat, hemispherical and conical nosed. The ballistic limit of the flat nosed projectile is the highest, while the impact performance of the conical and hemispherical nosed projectiles is obviously different from the flat nosed projectile, especially in a relative high velocity range. The sharper nose leads to a higher value of exit velocity and mass loss. In addition, effects of different design parameters on ballistic resistance were also studied by changing the thickness of honeycomb cell and face plates. Results indicate that the thickness of honeycomb walls and face plates have significant effect on the ballistic resistance and energy absorption in a relative low velocity range, while there are no big differences when the initial impact velocity exceeds 400 m/s.

Study on the performance of ceramic composite projectile penetrating into ceramic composite target

In order to study the performance of ceramic composite projectile penetrating into ceramic composite target, the contrast test and numerical simulations of the penetration of standard projectile and the ceramic composite projectile into a ceramic composite target were conducted. The results show that the penetration performance of ceramic composite projectile is obvious superior to that of standard projectile for ceramic composite target. The ceramic nose of ceramic composite projectile fully destroys the ceramic panels anterior to its following armor-piercing projectile body, thus maintaining the penetration ability of the following armor-piercing projectile body.