The ballistic performance of metal plates subjected to impact by projectiles of different strength

In this paper, the ballistic performance of monolithic, double- and three-layered steel plates impacted by projectiles of different strength is experimentally investigated by a gas gun. The ballistic limit velocity for each configuration target is obtained and compared based on the investigation of the effect of the number of layers and the strength of projectiles on the ballistic resistance. The results showed that monolithic plates had higher ballistic limit velocities than multi-layered plates for projectiles of low strength regardless their nose shape, and also the ballistic limit velocities of plates decreased with the increase of the number of layers. Moreover, monolithic plates showed greater ballistic limit velocities than multi-layered plates for ogival-nosed projectiles of high strength, and also the ballistic limit velocities of plates decreased with the increase of the number of layers. However, monolithic plates had lower ballistic limit velocities than multi-layered plates for blunt-nosed projectiles of high strength, and also the ballistic limit velocities of plates increased with the increase of the number of layers. The differences in the ballistic limit velocities between various impact conditions can be related to the transitions of perforation mechanisms and failure models of plates and projectiles.     

间隙对A3钢薄板抗卵形头弹侵彻性能影响的实验研究

为了分析板间间隙大小对双层板失效模式以及抗侵彻性能的影响,本文利用轻气炮进行了卵形杆弹正撞击单层板和等厚双层板的实验研究,得到了各种结构靶体的初始-剩余速度曲线和弹道极限速度。实验表明,对于卵形弹,单层板的弹道极限高于双层板的弹道极限,包括接触式和间隙式。当总厚度一定时,多层板的弹道极限随分层数目的增加而减小。此外,间隙大小对间隙式双层板的抗侵彻性能影响小,并且随着弹体初始速度的增加而减小。     

Ballistic Limit of Single and Layered Aluminium Plates

Abstract: This paper presents an experimental and finite‐element investigation of ballistic limit of thin single and layered aluminium target plates. Blunt‐, ogive‐ and hemispherical‐nosed steel projectiles of 19 mm diameter were impacted on single and layered aluminium target plates of thicknesses 0.5, 0.71, 1.0, 1.5, 2.0, 2.5 and 3 mm with the help of a pressure gun to obtain the ballistic limit in each case. The ballistic limit of target plate was found to be considerably affected by the projectile nose shape. Thin monolithic target plates as well as layered in‐contact plates offered lowest ballistic resistance against the impact of ogive‐nosed projectiles. Thicker monolithic plates on the other hand, offered lowest resistance against the impact of blunt‐nosed projectiles. The ballistic resistance of the layered targets decreased with increase in the number of layers for constant overall target thickness. Axi‐symmetric numerical simulations were performed with ABAQUS/Explicit to compare the numerical predictions with experiments. 3D numerical simulations were also performed for single plate of 1.0 mm thickness and two layered plate of 0.5 mm thickness impacted by blunt‐, ogive‐ and hemispherical‐nosed projectiles. Good agreement was found between the numerical simulations and experiments. 3D numerical simulations accurately predicted the failure mode of target plates.     

Ballistic performance of multi-layered metallic plates impacted by a 7.62-mm APM2 projectile

This paper presents a numerical investigation of the ballistic performance of monolithic, double- and triple-layered metallic plates made of either steel or aluminium or a combination of these materials, impacted by a 7.62-mm APM2 projectile in the velocity range of 775–950 m/s. Numerical models were developed using the explicit finite element code LS-DYNA. It was found that monolithic plates have a better ballistic performance than that of multi-layered plates made of the same material. This effect diminishes with impact velocity. It was also found that double-layered plates with a thin front plate of aluminium and thick back steel plate exhibit greater resistance than multi-layered steel plates with similar areal density. These predictions indicate that multi-layered targets using different metallic materials should be investigated for improved ballistic performance and weight-savings.     

Experimental study of perforation of multi-layered targets by hemispherical-nosed projectiles

In this paper, perforation of single and three layered metallic targets by hemispherical-nosed cylindrical projectiles are studied experimentally. The circular targets of Al 1100 have a diameter of 220 mm and the hemispherical-nosed projectiles are silver steel cylinders with a mass of 12.15 g which are hardened to 56RC. The single layer target is 3 mm thick and the thicknesses of layers of the three layered targets are 0.5, 1 and 1.5 mm. The multi-layered targets are tested both when the layers are in-contact and spaced (with air gaps). Tests are carried out using a one stage gas gun. The ballistic limit velocity is obtained and the effects of order of layers and the width of air gaps between them on the ballistic limit velocity are investigated. The results show that the single layer targets have greater ballistic limit velocities than multi-layered targets. Furthermore, the ballistic limit velocity of in-contact layered targets is greater than that of spaced layered targets.     

分层对TC4钛合金板抗平头弹撞击失效特性的影响

使用Abaqus/Explicit有限元分析软件,开展平头弹撞击不同厚度双层TC4钛合金板数值模拟,研究双层TC4钛合金板撞击失效特性与失效模式随厚度变化规律及机理。通过对比撞击试验与仿真结果,验证数值模型和参数的有效性。在此基础上与等厚度单层TC4钛合金板的抗侵彻性能进行对比,结果表明,对于12.68 mm直径的平头弹,在靶板厚度2~16 mm内,双层结构的弹道极限与总厚度近似呈线性关系。由于单层靶板在4~10 mm内随着厚度增加,弹道极限无明显变化,所以等厚接触式双层结构在该厚度范围相比单层靶有明显的优势。在总厚度为8 mm时,双层靶优势最为明显,弹道极限相比单层靶提高了43%左右。     

Q235钢单层板对平头刚性弹抗穿甲特性研究

采用撞击实验和理论模型对单层金属板的抗侵彻性能进行了研究,分析了靶体厚度对抗侵彻性能的影响。通过对比撞击实验和理论模型计算结果,验证了理论模型和参数的有效性。结果表明,采用合适的理论模型能够有效地预测靶板在弹体撞击下的弹道极限。此外,分析了靶体在弹体撞击下的塑性变形总耗能,包括靶板局部变形和整体变形的耗能,同时考虑了靶体材料的应变率效应。在平头弹撞击厚靶的工况中,引入了一个修正函数对靶体厚度进行修正。     

Ballistic resistance of double-layered armor plates

In this paper, the ballistic resistance of double-layered steel shields against projectile impact at the sub-ordnance velocity is evaluated using finite element simulations. Four types of projectiles of different weight and nose shapes are considered, while armor shields consist of two layers of different materials. In a previous study of the same authors, it was shown that a double-layered shield of the same metal was able to improve the ballistic limit by 7.0–25.0% under impact by a flat-nose projectile, compared to a monolithic plate of the same weight. Under impact by a conical-nose projectile, a double-layered shield is almost as capable as a monolithic plate. The present paper extends the analysis to double-layered shields with various metallic material combinations. The study reveals that the best configuration is the upper layer of high ductility and low strength material and the lower layer of low ductility and high strength material. This configuration results in some 25% gain in the ballistic limit under moderate detrimental impact. This research helps clarify the long standing issue of the ballistic resistance of the multi-layered armor configuration.     

Experimental and numerical study on the ballistic resistance of steel–fibre reinforced two-layer explosively welded plates

The damage mechanism and ballistic resistance of steel–fibres reinforced two-layer explosively welded steel/aluminum targets were investigated by the methods of ballistic experiments and numerical simulation by finite element code LS-DYNA 3D. Different from the traditional monolithic and multi-layer metal targets, there are reinforced steel–fibres and good surface-to-surface combination strength between layers of the target. The total thickness of the target was 5 mm and the diameter of the spherical steel fragments was 8 mm. The effects of layer thickness distribution and fibre density on the ballistic resistance were discussed. In addition, the ballistic resistance of composite target was compared with the same combination target without reinforced steel–fibres. The results show that the failure mode of steel front plate is shearing and plugging and that of aluminum rear plate is ductile prolonging deformation when the tied interface failed by tension (or shearing and plugging when the interface combination keep tied). Meanwhile, the steel–fibres failed by bending and tensile deformation. The V₅₀ value of target was maximum when the thickness ratio of steel front plate and aluminum rear plate was 3:1. The ballistic resistance of target with reinforced steel–fibres is generally better than that of the same thickness target without reinforced steel–fibres and the ballistic resistance decreased with the decrease of the fibre density.     

Impact response of sandwich plates with a pyramidal lattice core

The ballistic performance edge clamped 304 stainless-steel sandwich panels has been measured by impacting the plates at mid-span with a spherical steel projectile whose impact velocity ranged from 250 to 1300 m s⁻¹. The sandwich plates comprised two identical face sheets and a pyramidal truss core: the diameter of the impacting spherical projectile was approximately half the 25 mm truss core cell size. The ballistic behavior has been compared with monolithic 304 stainless-steel plates of approximately equal areal mass and with high-strength aluminum alloy (6061-T6) sandwich panels of identical geometry. The ballistic performance is quantified in terms of the entry and exit projectile velocities while high-speed photography is used to investigate the dynamic deformation and failure mechanisms. The stainless-steel sandwich panels were found to have a much higher ballistic resistance than the 6061-T6 aluminum alloy panels on a per volume basis but the ballistic energy absorption of the aluminum structures was slightly higher on a per unit mass basis. The ballistic performance of the monolithic and sandwich panels is almost identical though the failure mechanics of these two types of structures are rather different. At high impact velocities, the monolithic plates fail by ductile hole enlargement. By contrast, only the proximal face sheet of the sandwich plate undergoes this type of failure. The distal face sheet fails by a petalling mode over the entire velocity range investigated here. Given the substantially higher blast resistance of sandwich plates compared to monolithic plates of equal mass, we conclude that sandwich plates display a potential to outperform monolithic plates in multi-functional applications that combine blast resistance and ballistic performance.     

Ballistic limit for oblique impact of thin sandwich panels and spaced plates

Ballistic perforations of monolithic steel sheets, two-layered sheets and lightweight sandwich panels were investigated both experimentally and numerically. The experiments were performed using a short cylindrical projectile with either a flat or hemispherical nose that struck the target plate at an angle of obliquity. A total of 170 tests were performed at angles of obliquity 0–45°. The results suggest that during perforation by a flat-nosed projectile, layered plates cause more energy loss than monolithic plates of the same material and total thickness. There was no significant difference in the measured ballistic limit speed between monolithic plates and layered plates during oblique impact perforation by a hemispherical-nosed projectile.     

A study of the perforation of aluminium laminate targets

Experiments are described in which laminated aluminium alloy targets, of a variety of configurations, are perforated by flat-ended and conical penetrators. Target ballistic limit velocities are determined and the results are used to evaluate energy absorption mechanisms and to compare deformation and failure modes. It is demonstrated by modelling that increasing the numbers of layers in multi-layer targets increases the tensile stretching work in perforation. However, since this is accompanied by reductions in other work terms, only small changes are found in total energy absorption, despite large changes in failure geometry. The propensity to stretch and bend or to shear a plug is affected by target exit-side layer thickness relative to projectile diameter, with thick layers tending to favour plugging by a shear mechanism. In targets with thin exit-side layers tensile, rather than shear, mechanisms are apparent in failure and plug separation. A model is developed which treats the perforation of laminates as a two-stage process of indentation on the impact side, and either shear or dishing failure on the exit side, depending on target configuration. For the cases examined the model gives good predictions of the ballistic limit, including distinguishing between differently configured laminates, and correctly accounts for the effect of projectile nose shape. As part of this process, the estimation of dishing energies is improved by accounting for the effect of tangential curvature. In spite of its success in predicting ballistic limits, the model involves some simplifications which do not mirror experimental observations. A notable example is its neglect of the detailed geometric features of deformation. Nevertheless, the model can be used to elucidate design features for laminated targets.     

Perforation of AA5083-H116 aluminium plates with conical-nose steel projectiles—experimental study

The interest regarding use of aluminium alloys in lightweight protective structures is today increasing. Even so, the number of experimental and computational investigations giving detailed information on such problems is still rather limited. In this paper, perforation experiments have been performed on AA5083-H116 aluminium plates with thicknesses varying between 15 and 30 mm impacted by 20 mm diameter, 98 mm long, HRC 53 conical-nose hardened steel projectiles. In all tests, initial and residual velocities of the projectile were measured and a digital high-speed camera system was used to photograph the penetration and perforation process. Based on these measurements, impact versus residual velocity curves of the target plates were constructed and the ballistic limit velocity of each target was obtained. An analytical perforation model from the open literature is then used to predict the ballistic limit velocity, and excellent agreement with the experimental data is found. The experimental results are finally compared to similar experiments on steel and concrete targets, and the capacity of the different materials is evaluated in relation to total weight.     

Experimental investigation of the ballistic resistance of steel-fiberglass reinforced polyester laminated plates

The present experimental study is undertaken to investigate the effect of target configuration on ballistic performance when struck by standard bullets of different velocities. At first, single mild steel plates, 1–8 mm thick, are tested, and the effect of thickness and mechanical properties of plate material are explored. Secondly, in-contact laminae comprising an 8 mm-thick target, and spaced laminae of the same total steel thickness, with spacing distances equal to or multiples of the bullet core diameter (6 mm) are tested and the effect of number, thickness, and arrangement of laminae sought.In addition, fiberglass reinforced polyester (FRP) is used as a filler material for targets with spaced steel laminae. The influence of FRP's physical and mechanical properties on the ballistic performance of steel-FRP targets is investigated.In order to perform the ballistic tests, a special setup is constructed, which consists of a launcher, a target clamp and a velocity-measuring device. In each experiment, the change in the projectile velocity (while penetrating the target) divided by the length of penetration is established as a measure of target performance.Results show that single targets are more effective than laminated targets of the same total thickness, regardless of the configuration or striking velocity. It is noted, however, that the difference in performance diminishes as the striking velocity increases. Moreover, the effectiveness of laminated targets, in contact or spaced, increases as the number of laminae comprising each target decreases. Ballistic performance of laminated targets is further enhanced by using the thickest lamina as the back lamina. Results also emphasize the dependence of target performance on mechanical properties.Steel-FRP targets show better performance than weight-equivalent steel targets. Performance of a steel-FRP target is further improved by increasing fiber weight fraction in the FRP.     

Normal impact of ogive nosed projectiles on thin plates

Single plates of aluminium of various thicknesses were subjected to normal impact by ogive nosed projectiles at velocities normally greater than their ballistic limit. The observed values of the residual velocity and ballistic limit are presented and influence thereon of various parameters is discussed. Based on the mechanism of deformation observed and the data of residual and incident velocities, analytical and empirical relations have respectively been developed for the determination of both residual velocity and ballistic limit. These relations are seen to match the experiments well.     

Comparative analysis of oblique impact on ceramic composite systems

An experimental programme is presented which investigated the performance of oblique, ceramic/metal, bilayer composite armours. The ceramics, alumina and silicon carbide, were backed by either Rolled Homogeneous Armour steel (RHA) or 7000 series aluminium. Using a model scale tungsten penetrator at two velocities (representing current and future ordnance threats) the effect of configuration on ballistic limit or depth of penetration (DOP) areal densities was determined. Areal densities of the DOP targets decreased with increasing ceramic thickness, achieving a minimum at zero residual penetration in the backing. The bilayer targets, loaded at the ballistic limit needed a larger areal density to defeat the penetrator. This areal density also decreased with ceramic thickness but showed a minimum with respect to ceramic thickness, as a result of reduced support by the thinner metallic backing. At 1450ms⁻¹ the most efficient system was found to be a SiC/Al, which demonstrated a 25% weight saving over the monolithic aluminium reference target. The Al-alloy backing performs better than RHA, and SiC better than Al₂O₃.     

Observations on shear plug formation in Weldox 460 E steel plates impacted by blunt-nosed projectiles

Shear plug formation in circular Weldox 460 E steel plates impacted by blunt-nosed cylindrical projectiles with striking velocities between 100 and 500 m/s has been investigated. Target thickness and projectile impact velocity were the primary variables, and for each target thickness the ballistic limit curve of the material was precisely determined. The test at an impact velocity just below the ballistic limit for each target thickness was selected for a microscopic examination of shear localisation and fracture. In these tests, the plug was pushed only partway through the target, and the localised shear zones outlining the fracture were easily recognised both in the optical and scanning electron microscope. Clear evidence of adiabatic shear bands and material damage due to void growth was found in several of the target plates. Analytical models available in the literature were compared with the results from the experimental and microscopic studies. Reasonable agreement was found between calculations and experiments.     

半球形头弹不同角度冲击下编织复合材料板的侵彻特性

利用一级气炮发射半球形头弹冲击2 mm厚的编织复合材料层合板,冲击角度为0°、30°和45°,通过高速相机记录弹靶撞击过程并得到弹体速度数据。利用拟合公式处理试验数据,得到不同冲击角度时的弹道极限值,并和理论模型结果进行对比。分析了冲击角度对靶板弹道极限、能量吸收率和失效模式的影响。结果表明：45°斜冲击时的靶板弹道极限最高,正冲击次之,30°斜冲击最低。相同冲击能量时,45°斜冲击的能量吸收率最高,低能量（<80 J）冲击时,30°斜冲击比正冲击能量吸收率高,高能量（>80 J）时,正冲击更高。正冲击时,靶板正面因剪切失效而形成圆形凹坑,背面因纤维拉伸失效形成菱形鼓包,斜冲击形成椭圆形扩孔,且其面积随冲击角度增加而增加。     

Ballistic resistance of spaced multi-layer plate structures: Experiments on Fibre Reinforced Plastic targets and an analytical framework for calculating the ballistic limit

As the use of complex multi-layer structures in defense, marine, aerospace and automotive applications becomes increasingly common, it is vital that the response of such structures to impact loading is better understood and that engineers have adequate analysis tools to design structures optimised for resistance to ballistic penetration. This paper presents the results of a series of ballistic impact experiments carried out on a range of spaced multi-layer fibre reinforced-plastic (FRP) composite targets, with a constant total number of plies per target, but varying numbers of plies per layer and varying layer arrangements. It is shown that varying the ratio of plies between layers can have a significant effect on resistance to ballistic penetration. In light of these experimental results, the validity of applying the Lambert–Jonas equation to spaced multi-layer structures is discussed and an extended framework developed to determine the ballistic limit of a projectile impacting such a structure. The extended Lambert–Jonas framework is then validated with data from the literature. It is hoped that this framework will allow engineers to quickly determine the optimum layer arrangement to maximise the ballistic resistance of complex spaced multi-layer structures.     

Ti/Al3Ti金属间化合物基层状复合材料抗侵彻性能数值模拟

采用LS-DYNA非线性有限元软件对Ti/Al₃Ti金属间化合物基层状（MIL）复合材料靶板的弹道侵彻过程进行了数值模拟。考察了等厚度下Ti体积分数、层数和材料梯度分布对复合材料抗侵彻性能的影响。结果表明,Ti体积分数约为20%时,靶板的抗侵彻性能最好。随着层数的增加,复合材料靶板的抗侵彻性能逐渐增强;但超过25层后,靶板的抗侵彻性能逐渐趋于稳定。不同铺层结构功能梯度板的抗侵彻性能相差较大,正向铺层梯度板的抗侵彻性能明显优于等厚均质复合材料靶板。