Fragment Simulating Projectile Research Articles

Kompozyt warstwowy zwiększający odporność samochodów patrolowych i interwencyjnych na atak improwizowanych ładunków wybuchowych (IED) od dołu

Model layered composites were made of polyester resin reinforced with layers of glass fibre and aramid fibre fabrics. The fabrics for the study were selected in a manner enabling the comparison of their ballistic resistance depending on the material type and density. Additionally, aluminium plates were used to produce the composites.The study examined the resistance of the model composites to 1.1 g fragment simulating projectile (FSP) penetration, their susceptibility to deformation caused by shock waves produced by pure TNT charges, and their resistance to the effects of detonation of model improvised explosive devices (IED) containing fragments in the form of bearing balls. The analysis and optimisation of the test results enabled the selection of a layer configuration combining the materials studied that has the lowest area density and that protects car bottom structures against perforation in the case of a detonation of a small improvised explosive device.

Modeling and Experiments on Ballistic Impact into UHMWPE Yarns Using Flat and Saddle-Nosed Projectiles

Yarn shooting experiments were conducted to determine the ballistically-relevant, Young’s modulus and tensile strength of ultra-high molecular weight polyethylene (UHMWPE) fiber. Target specimens were Dyneema® SK76 yarns (1760 dtex), twisted to 40 turns/m, and initially tensioned to stresses ranging from 29 to 2200 MPa. Yarns were impacted, transversely, by two types of cylindrical steel projectiles at velocities ranging from 150 to 555 m/s: (i) a reverse-fired, fragment simulating projectile (FSP) where the flat rear face impacted the yarn rather than the beveled nose; and (ii) a ‘saddle-nosed projectile’ having a specially contoured nose imparting circular curvature in the region of impact, but opposite curvature transversely to prevent yarn slippage off the nose. Experimental data consisted of sequential photographic images of the progress of the triangular transverse wave, as well as tensile wave speed measured using spaced, piezo-electric sensors. Yarn Young’s modulus, calculated from the tensile wave-speed, varied from 133 GPa at minimal initial tension to 208 GPa at the highest initial tensions. However, varying projectile impact velocity, and thus, the strain jump on impact, had negligible effect on the modulus. Contrary to predictions from the classical Cole-Smith model for 1D yarn impact, the critical velocity for yarn failure differed significantly for the two projectile types, being 18% lower for the flat-faced, reversed FSP projectile compared to the saddle-nosed projectile, which converts to an apparent 25% difference in yarn strength. To explain this difference, a wave-propagation model was developed that incorporates tension wave collision under blunt impact by a flat-faced projectile, in contrast to outward wave propagation in the classical model. Agreement between experiment and model predictions was outstanding across a wide range of initial yarn tensions. However, plots of calculated failure stress versus yarn pre-tension stress resulted in apparent yarn strengths much lower than 3.4 GPa from quasi-static tension tests, although a plot of critical velocity versus initial tension did project to 3.4 GPa at zero velocity. This strength reduction (occurring also in aramid fibers) suggested that transverse fiber distortion and yarn compaction from a compressive shock wave under the projectile results in fiber-on-fiber interference in the emerging transverse wave front, causing a gradient in fiber tensile strains with depth, and strain concentration in fibers nearest the projectile face. A model was developed to illustrate the phenomenon.

Role of Inelastic Transverse Compressive Behavior and Multiaxial Loading on the Transverse Impact of Kevlar KM2 Single Fiber

High-velocity transverse impact of ballistic fabrics and yarns by projectiles subject individual fibers to multi-axial dynamic loading. Single-fiber transverse impact experiments with the current state-of-the-art experimental capabilities are challenging due to the associated micron length-scale. Kevlar® KM2 fibers exhibit a nonlinear inelastic behavior in transverse compression with an elastic limit less than 1.5% strain. The effect of this transverse behavior on a single KM2 fiber subjected to a cylindrical and a fragment-simulating projectile (FSP) transverse impact is studied with a 3D finite element model. The inelastic behavior results in a significant reduction of fiber bounce velocity and projectile-fiber contact forces up to 38% compared to an elastic impact response. The multiaxial stress states during impact including transverse compression, axial tension, axial compression and interlaminar shear are presented at the location of failure. In addition, the models show a strain concentration over a small length in the fiber under the projectile-fiber contact. A failure criterion, based on maximum axial tensile strain accounting for the gage length, strain rate and multiaxial loading degradation effects are applied to predict the single-fiber breaking speed. Results are compared to the elastic response to assess the importance of inelastic material behavior on failure during a transverse impact.

Ballistic Impact Behaviour of Thermoplastic Kevlar Composites: Parametric Studies

The objective of the present study is to investigate the ballistic impact behavior of Kevlar/Polypropylene (PP) composites through hydrocode simulations performed in ANSYS AUTODYN-2D/3D. The studies are carried out based on the experimental and numerical investigation of ballistic impact response of Kevlar/PP composites reported in our recent work [Bandaru et al. Ballistic impact response of Kevlar® reinforced thermoplastic composite armors, Int J Impact Eng 2016;89:1-13]. The interface between the Kevlar and PP matrix is improved by adding polypropylene grafted with Maleic anhydride. The numerical model is validated by evaluating the ballistic impact performance of Kevlar/PP composites when impacted with STANAG-2920 fragment simulating projectile (FSP). Kevlar/PP showed improved ballistic impact performance than that of the Kevlar/Vinylester composite reported in the literature. Numerical simulations are further extended to study the influence of the mass of the projectile on the ballistic impact performance of Kevlar/PP composite armors in terms of ballistic limit, energy absorption and residual velocity. It is observed that shear plugging is the dominant failure mechanism in thermoplastic composites.

Finite Element Simulation of Impact on PASGT Army Helmet

This paper presents the numerical simulations to determine the impact resistance of Personal Armor System Ground Troops (PASGT) helmet. Initially impact of spherical projectile on PASGT helmet travelling at 205 m/s is studied. The result of this simulation was used to verify the material data and compare the work with previous literature. Two standard tests, namely the MIL-H-44099A and NIJ-STD-0106.01 Type II helmet are also simulated. For the simulation on MIL-H-44099A, a fragment-simulating projectile (FSP) strikes the helmet with an impact velocity of 610 m/s. For the simulation on NIJ-STD-0106.01 Type II helmet, the projectile is a 9mm full-jacketed bullet with a striking velocity of 358 m/s. Results from the simulation show that the KEVLARs helmet is able to resist a 9mm full-jacketed bullet travelling at 358 m/s. The above simulations were performed using Finite Element Method in explicit formulation, implemented through Ansys AUTODYN-3D.

The high-velocity impact of Dyneema® and Spectra® laminates: implementation of a simple thermal softening model

The commercial hydrocode ANSYS AUTODYN® was used to create a thermally dependent model of an Ultra-High Molecular Weight Polyethylene (UHMW-PE) composite under high and hypervelocity impact. In particular this model was validated against high-velocity fragment-simulating projectile (FSP) impacts and hypervelocity polycarbonate cylinder impacts at 2,100 m/s and 3,500 m/s. It appeared that despite the same material model being used for thick unidirectional Dyneema® laminates and thin woven Spectra® laminates, the model showed reasonable correlation in all cases. This suggests that modelling results from these types of studies are not sensitive to the exact parameters used in the material model.

Influence of multiaxial loading on the failure of Kevlar KM2 single fiber

The role of multiaxial loading on the failure of Kevlar® KM2 ballistic fibers during transverse loading is not well understood. Quasi-static experiments reported by Hudspeth M, Li D, Spatola J, et al. (2015) on single KM2 fiber subjected to transverse loading by three indenter geometries over a wide range of loading angles exhibit significant reductions in the average axial tensile failure strain. In this study, a three-dimensional finite element model is developed to predict the degree of multiaxial loading present at the location of fiber failure in these experiments. The model predicts an axial tensile strain concentration within the indenter–fiber contact zone. The fiber is also subjected to multiaxial stress/strain states within the contact zone consisting of axial tension, axial compression, transverse compression and interlaminar shear that can degrade axial tensile failure strain. For a round indenter with a radius much higher than the fiber diameter, the axial tensile strain concentration and multiaxial strain in the fiber are negligible. In the case of a fragment-simulating projectile and a razor indenter, significant axial tensile strain concentrations (2.2–5.9) are predicted and the localized transverse loading results in extensive inelastic deformation within the fiber cross-section. Based on the results, a maximum axial tensile strain failure criterion incorporating the multiaxial loading degradation effects is developed. The failure criterion correlates well with the experimental measurements reported by Hudspeth et al. for all three indenters. Modeling the experiments provides new insights into the tensile failure strain of high-performance ballistic fibers at extremely small gage lengths subject to transverse impact loading.

Development of numerical model for ballistic resistance evaluation of combat helmet and experimental validation

Modern designing process of combat helmets requires both numerical modeling and experimental validation in order to achieve exigent requirements combining impact resistance and reasonable weight. In this work a finite element model of a combat helmet is presented. Mechanical behaviour of the shell aramid composite under impact conditions was analyzed from experimental Fragment Simulating Projectile (FSP) and Full-Metal Jacketed (FMJ) impact tests on aramid flat plates. Numerical modeling based on finite elements method was used to simulate both impacts in simple plates of the composite and also the simulation of ballistic impact involving real ammunition and the complex geometry of the helmet including inner foam. Experimental work involving impact tests on composite plates and also ballistic test on the helmet with a dummy provided real data for comparison with models predictions and proved the accuracy of the numerical models developed.

The ballistic performance of an ultra-high hardness armour steel: An experimental investigation

The ballistic performance of an ultra-high hardness armour steel (UHA) has been evaluated for a range of thicknesses and obliquities against armour piercing (AP) and fragment simulating projectiles (FSPs). Together with published literature, these results enable the effect of plate hardness on performance against both AP and FSP threats to be characterized over a range of plate hardnesses from ~ 300 to 600 HB. For AP projectiles, a complex relationship was observed that corresponded well with historical phenomenological curves describing the effect of varying projectile and armour failure mechanisms. In the ultra-high hardness regime (> 570 HB), against AP projectiles with core hardnesses of 610–745 HB (i.e. 7.62 mm APM2 and 12.7 mm APM2 projectiles), projectile shatter was demonstrated to be the controlling mechanism of armour performance. Against much softer FSPs (281 HB), where projectile shatter is not a relevant mechanism, the armour performance was found to initially decrease with increasing plate hardness up to ~ 450 HB due to increased susceptibility to adiabatic shear plugging. Above ~ 450 HB the performance was observed to plateau. The observed performance plateau appears to relate to a critical threshold for adiabatic shear failure beyond which further increases in plate hardness will not result in a decrease in performance. A number of common empirical and analytical models were applied to reproduce the experimentally-determined relationship between hardness and penetration resistance, none of which were able to qualitatively or quantitatively reproduce the observed relationships for either projectile class.

Investigating ballistic impact properties of woven kenaf-aramid hybrid composites

In this study, the ballistic impact performance of woven kenaf-Kevlar hybrid and non-hybrid composites against fragment simulating projectiles (FSPs) was investigated. All the composites were prepared using the hand lay-up technique, method, followed by static load compression. The hybrid composites consist of Kevlar fabric and woven kenaf layers. The results obtained indicate that the energy absorption, ballistic limit velocity (V 50) and failure behaviour of the composites during the impact event were affected by the woven kenaf hybridisation. The additional kenaf layers in hybrid composites resulted in the increase in composites thickness and areal density, thus increased the energy absorption (14.46 % to 41.30 %) and V 50 (5.5 % to 8.44 %). It was observed that the hybrid composites failed through a combination of fibre shear, delamination and fibre fracture in the impacted surface, woven kenaf-Kevlar interface and rear surface respectively. Although the specific energy absorption was lower for the hybrid composites, further investigations need to be carried out to utilise the great potential natural fibres.

A methodology for hydrocode analysis of ultra-high molecular weight polyethylene composite under ballistic impact

Ballistic performance analysis of ultra-high molecular weight polyethylene (UHMW-PE) is critical for the design of armour systems against ballistic threats. However, no validated modelling strategy has been published in literature for UHMW-PE composite that captures the penetration and damage mechanisms of thick targets impacted between 900m/s and 2000m/s. Here we propose a mechanistically-based and extensively validated methodology for the ballistic impact analysis of thick UHMW-PE composite. The methodology uses a non-linear orthotropic continuum model that describes the composite response using a non-linear equation of state (EoS), orthotropic elastic–plastic strength with directional hardening and orthotropic failure criteria. A new sub-laminate discretisation approach is proposed that allows the model to more accurately capture out-of-plane failure. The model is extensively validated using experimental ballistic data for a wide range of UHMW-PE target thicknesses up to 102mm against 12.7mm and 20mm calibre fragment simulating projectiles (FSPs) with impact velocities between 400m/s and 2000m/s. Very good overall agreement with experimental results is seen for depth of penetration, ballistic limit and residual velocity, while the penetration mechanisms and target bulge behaviour are accurately predicted. The model can be used to reduce the volume of testing typically required to design and assess thick UHMW-PE composite in ballistic impact applications.

Penetration resistance and ballistic-impact behavior of Ti/TiAl<sub>3</sub> metal/intermetallic laminated composites (MILCs): A computational investigation

A comprehensive computational engineering analysis is carried out in order to assess suitability of the Ti/TiAl3 metal/intermetallic laminated composites (MILCs) for use in both structural and add-on armor applications. This class of composite materials consists of alternating sub-millimeter thick layers of Ti (the ductile and tough constituent) and TiAl3 (the stiff and hard constituent). In recent years, this class of materials has been investigated for potential use in light-armor applications as a replacement for the traditional metallic or polymer-matrix composite materials. Within the computational analysis, an account is given to differing functional requirements for candidate materials when used in structural and add-on ballistic armor. The analysis employed is of a transient, nonlinear-dynamics, finite-element character, and the problem investigated involves normal impact (i.e. under zero obliquity angle) of a Ti/TiAl3 MILC target plate, over a range of incident velocities, by a fragment simulating projectile (FSP). This type of analysis can provide more direct information regarding the ballistic limit of the subject armor material, as well as help with the identification of the nature and the efficacy of various FSP material-deformation/erosion and kinetic-energy absorption/dissipation phenomena and processes. The results obtained clearly revealed that Ti/TiAl3 MILCs are more suitable for use in add-on ballistic, than in structural armor applications.

NUMERICAL MODELING OF THE BALLISTIC LIMIT IN THE HYDRODYNAMIC RAM

This paper presents the ballistic limit study for the water-filled aluminum tank. The objective was to determine the ballistic limit for the rear tank wall by using numerical method. Commercial software Altair Hyperworks 12.0 was employed for this study. The finite element coupled with smoothed particle hydrodynamics (SPH) was developed to model the perforation of fragment simulating projectile (FSP) towards water-filled tank. Verification of the results was done by comparing with the experiment results. The results showed that there were four main phase failures occurred, which were shock phase, drag phase, cavitation phase and exit phase. The ballistic limit for the rear wall was 479.27 m/s.

Perforation of aluminum plates by fragment simulating projectiles (FSP)

The paper describes the ballistic impact test, in which fragment simulating projectiles (FSPs) of a 20-mm-diameter have been used against 40-mmthick plates made of an aluminum alloy AA7020-T651. To perforate plates, the projectiles must have reached a velocity higher than 890 m/s. Based on the performed ballistic test, the plugging failure mode is numerically modeled using the LS-DYNA software package. Results obtained due to the calculations in the Finite Element Method (FEM) are compared with the results from the Smoothed Particle Hydrodynamics (SPH). A condition of geometrical similarity between the target deformed experimentally and its numerical representation is introduced to evaluate the performed simulations.

Experimental and numerical investigation of a 3D woven fabric subjected to a ballistic impact

This paper focuses on validating a numerical modelling of woven materials subjected to ballistic impact based on experimental data. Studied impact system is a 3D warp interlock fabric (4 layers of angle interlock – through the thickness) and FSP projectile (Fragment Simulating Projectile). Numerical prediction is compared with ballistic tests on data obtained from ultra-rapid camera in two typical impact cases: no perforation and perforation. Effect of deformation rate is investigated by using both mechanical properties of yarn in static and dynamic states for numerical modelling. The numerical model using dynamic parameters shows a better prediction of impact behaviour of the 3D woven fabric than the one using static parameters.

Thick AA7020-T651 plates under ballistic impact of fragment-simulating projectiles

The ballistic performance of an Al alloy AA7020-T651 (AlZn4.5Mg1, 3.4335) against fragment-simulating projectiles (FSPs) is investigated at impact velocities between 900 m/s and 1500 m/s. The target plates are considered as thick regarding the ratio between the specimen thickness (40 mm) and the projectile diameter (20 mm). With increasing impact velocities, the observed failure modes of the target plates change from plugging to discing. The stress state leading to the discing formation has been described and numerically modeled by the Lagrangian approach. In order to understand the mechanisms that occur in the material under highly dynamic loadings, its mechanical, thermal and micro-structural properties are discussed. The experimental conditions (thick target, penetrator of a specific shape, high-velocity impacts) allow the authors to draw conclusions, which are complementary to those that resulted from investigations of semi-thick and thin target plates under ballistic impacts in a lower velocity range.

Ballistic impact response of Ultra-High-Molecular-Weight Polyethylene (UHMWPE)

In this paper we report findings from ballistic experiments conducted on Ultra-High-Molecular-Weight Polyethylene (UHMWPE) flat panels. We measured ballistic limit velocities, V50 of panels of different thicknesses using a fragment simulating projectile (FSP) and characterized back face deformation (BFD) using a spherical projectile. UHMWPE panels with different architectures (hybrid and non-hybrid) were evaluated. For the back face deformation (BFD) experiments, the thickness of post-impact intact material and interior delamination were characterized using X-ray Computer Tomography method. These measurements were used to evaluate the effects of fiber orientation and boundary constraints on material deformation and failure response to ballistic loading conditions. The expansion rate of the back face deformation zone in the transverse direction (to the direction of impact) decreased with time. This transverse expansion speed was higher in hybrid panels compared to the [0/90] cross-ply panels, which resulted in earlier influence of boundary constraints on back face deformation for hybrid panels. One major delamination occurred in the hybrid panels at cross-ply [0/90] and non-cross ply interface. The lateral extent of this delamination was larger when the panel edges were clamped as compared to the free panel edge case.

The Efficiency of Ultra-High Molecular Weight Polyethylene Composite Against Fragment Impact

This paper presents an experimental investigation into the ballistic resistance of ultra-high molecular weight polyethylene (UHMW-PE) composite, and compares its performance against a range of common metallic and composite armour materials. An extensive experimental program was conducted to determine the ballistic limit velocity (V50) of UHMW-PE composite against 12.7 and 20 mm fragment simulating projectiles (FSPs) for a wide range of thicknesses. For protection against these projectiles, UHMW-PE composite was found to be consistently more mass efficient than rolled homogeneous armour steel (RHA), high hardness armour steel (HHA), aluminium alloy 5059-H131, and polymer composites reinforced with aramid, glass or carbon fibres. In terms of armour space claim, UHMW-PE composite was found to be less efficient than both steel types and glass fibre-reinforced plastic, though it was comparable to aramid fibre-reinforced plastic, and was more efficient than aluminium 5059-H131 and carbon fibre-reinforced plastic. Scaling effects were observed that showed metals were more effective against smaller projectiles in terms of armour mass required to stop a given projectile kinetic energy. These effects were not observed to the same extent for UHMW-PE composite, giving rise to a higher UHMW-PE mass efficiency against larger projectiles.

A comparison of the ballistic performance of shear thickening fluids based on particle strength and volume fraction

The ballistic response of suspensions of solid particles (cornstarch, silicon carbide, and silicon dioxide) in a liquid (ethylene glycol) is experimentally investigated. Some of the suspensions are at sufficient volume fraction to exhibit shear-thickening behaviour, while the others are Newtonian or mildly shear-thinning. The response of neat (liquid) ethylene glycol is also studied. Capsules containing the suspensions are impacted with a chisel-nosed fragment-simulating projectiles at velocities between 200 and 700 m/s. The residual projectile velocity upon exit from the capsule is measured via direct videography. The results are analysed using a number of different energy-based and momentum-based penetration models. A momentum-based model that normalizes the effect of the density of the suspension is seen to perform the best in terms of collapsing the results onto a single curve for the liquid and non-shear thickening suspensions. Only shear thickening suspensions with particles having sufficient strength (SiO2 and SiC) show significant deviation from hydrodynamic-dominated response, resulting in significant velocity decrements in the projectile attributable to the shear strength of the suspensions. These shear strength effects diminish as the projectile velocity increases, suggesting that the strength of the solid material in the interparticle contacts is overcome by the impact-generated stresses.

The effect of target thickness on the ballistic performance of ultra high molecular weight polyethylene composite

The ballistic performance of thick ultra-high molecular weight polyethylene (UHMW-PE) composite was experimentally determined for panel thicknesses ranging from 9 mm to 100 mm against 12.7 mm and 20 mm calibre fragment simulating projectiles (FSPs). Thin panels (∼<10 mm thick) were observed to undergo large deflection and bulging, failing predominantly in fibre tension. With increased thickness the panels demonstrated a two-stage penetration process: shear plugging during the initial penetration followed by the formation of a transition plane and bulging of a separated rear panel. The transition plane between the two penetration stages was found to vary with impact velocity and target thickness. These variables are inter-related in ballistic limit testing as thicker targets are tested at higher velocities. An analytical model was developed to describe the two-stages of perforation, based on energy and momentum conservation. The shear plugging stage is characterised in terms of work required to produce a shear plug in the target material, while the bulging and membrane tension phase is based on momentum and classical yarn theory. The model was found to provide very good agreement with the experimental results for thick targets that displayed the two-stage penetration process. For thin targets, which did not show the initial shear plugging phase, analytical models for membranes were demonstrated as suitable.