The influence of projectile hardness on ballistic performance

The ballistic performance of 17 penetrator materials, representing 5 distinct steel alloys treated to various hardnesses along with one tungsten alloy, has been investigated. Residual lengths and velocities, as well as the ballistic limit velocities, were determined experimentally for each of the alloy types for length-to-diameter (L/D) ratio 10 projectiles against finite-thick armor steel targets. The target thickness normalized by the projectile diameter (T/D) was 3.55. For some of the projectile types, a harder target, with the same thickness, was also used. It was found that the ballistic limit velocity decreases significantly when the projectile hardness exceeds that of the target. Numerical simulations are used to investigate some of the observed trends. It is shown that the residual projectile length is sensitive to projectile hardness; the numerical simulations reproduce this experimental observation. However, the observed trend in residual velocity as a function of projectile hardness is not reproduced in the numerical simulations unless a material model is invoked. It is assumed that the plastic work per unit volume is approximately a constant, that is, there is a trade off between strength and ductility. Using this model, the numerical simulations reproduce the experimentally observed trend.     

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.     

低合金船用结构钢抗高速破片能力研究EI

利用14.7mm口径滑膛弹道枪试验研究10g高速破片模拟弹侵彻不同厚度的低合金船用结构钢。根据弹道试验得到的剩余速度、单位面密度吸能值,分析得到钢板的单位面密度吸能量S、高速破片剩余速度vr与初始速度v0、厚度h的计算关系式。经试验验证,证明经验公式的预测结果与弹道试验结果有较好的吻合。     

Experimental investigation on the ballistic resistance of monolithic and multi-layered plates against ogival-nosed rigid projectiles impact

In this paper, the ballistic performance of single, two-, three- and four-layered steel plates impacted by ogival-nosed projectiles were experimentally investigated. Thin multi-layered plates arranged in various combinations of the same total thicknesses were normally impacted with the help of a gas gun. Ballistic limit velocity for each configuration target was obtained and compared based on the investigation of the effect of the air gap between layers, the number, order and thickness of layers on the ballistic resistance of targets. The results show that the thin monolithic targets have greater ballistic limit velocities than multi-layered targets if the total thickness less than a special value, and also the ballistic limit velocities of multi-layered targets decrease with the increase of the number of layers. Otherwise, the moderate thickness monolithic targets give lower ballistic limit velocities than multi-layered targets. Furthermore, the ballistic limit velocities of in-contact multi-layered targets are greater than those of spaced multi-layered targets. The order of layers affects the ballistic limit velocities of multi-layered targets, the ballistic resistance of the multi-layered targets is better when the first layer is thinner than the second layer.     

Dynamic penetration of graphite/epoxy laminates impacted by a blunt-ended projectile

The dynamic penetration of graphite/epoxy laminates as a result of impact by a blunt-ended projectile is investigated in the present study. The ballistic limit is determined by a series of high-velocity impact tests. A dynamic finite element analysis is performed to simulate the penetration process in composite laminates. A previously developed static penetration model is incorporated into the analysis to predict the ballistic limit. The ballistic characteristics are represented by the relationship between the striking and residual velocities of the projectile. Good agreement between experimental data and computational results implies that the ballistic limit of graphite/epoxy laminates can be predicted by the present analysis without performing dynamic impact tests.     

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 equations in ballistic and shatter regions

Ballistic limit equations are used to predict the damage of spacecraft subjected to impacts by space debris and meteoroids. This paper presents two new ballistic limit equations for impact velocities in the ballistic and shatter regions, respectively. The methodology used to develop the two ballistic limit equations involves the energy balance law and Cohen's debris cratering model. A very often form for ballistic limit equations based on the crater depth in a semi-infinite target was used for the both equations. The limit velocity between the ballistic and shatter regions was expressed as a non-dimensional equation in this paper. Agreement observed between existing and proposed results confirmed the validity of the presented equations.     

Perforation of aluminum plates with ogive-nose steel rods at normal and oblique impacts

Perforation experiments were conducted with 26.3 mm thick, 6061-T651 aluminum plates and 12.9 mm diameter, 88.9 mm long, 4340 R_c = 44 ogive-nose steel rods. For normal and oblique impacts with striking velocities between 280 and 860 m/s, we measured residual velocities and displayed the perforation process with X-ray photographs. These photographs clearly showed the time-resolved projectile kinematics and permanent deformations. In addition, we developed perforation equations that accurately predict the ballistic limit and residual velocities.     

A fracture mechanics approach to the residual strength behavior of ballistically damaged high hardness laminar composite steel

Welded and unwelded specimens of an air-melted laminar composite steel armor were tested for degradation of strength from ballistic impact. Specimens were impacted with cal. 0.30 AP and ball projectiles at various velocities and 0-degree obliquity. During impact, specimens were tensile loaded from 0 psi to the preload that would result in specimen failure at impact. Specimens that did not fail upon impact were pulled to failure to determine residual strength.

Damage due to cal. 0.30 impact maximized at approx. 2.25 in. laterally for ball and 1 in. for AP at a velocity near the ballistic limit. Preload increased the damage slightly. Impacts near the weld produced no detectable degradation of the weld.

Damage near the maximum resulted in residual strengths near 20% of the original σ_M. Fracture mechanics analysis showed that residual strengths could reasonably be predicted by assuming that all damage could be modeled as a center notch through the hard face.     

Quasi-brittle fracture during structural impact of AA7075-T651 aluminium plates

The stress–strain behaviour of the aluminium alloy 7075 in T651 temper is characterized by tension and compression tests. The material was delivered as rolled plates of thickness 20 mm. Quasi-static tension tests are carried out in three in-plane directions to characterize the plastic anisotropy of the material, while the quasi-static compression tests are done in the through-thickness direction. Dynamic tensile tests are performed in a split Hopkinson tension bar to evaluate the strain-rate sensitivity of the material. Notched tensile tests are conducted to study the influence of stress triaxiality on the ductility of the material. Based on the material tests, a thermoelastic–thermoviscoplastic constitutive model and a ductile fracture criterion are determined for AA7075-T651. Plate impact tests using 20 mm diameter, 197 g mass hardened steel projectiles with blunt and ogival nose shapes are carried out in a compressed gas-gun to reveal the alloy's resistance to ballistic impact, and both the ballistic limit velocities and the initial versus residual velocity curves are obtained. It is found that the alloy is rather brittle during impact, and severe fragmentation and delamination of the target in the impact zone are detected. All impact tests are analysed using the explicit solver of the non-linear finite element code LS-DYNA. Simulations are run with both axisymmetric and solid elements. The failure modes are seen to be reasonably well captured in the simulations, while some deviations occur between the numerical and experimental ballistic limit velocities. The latter is ascribed to the observed fragmentation and delamination of the target which are difficult to model accurately in the finite element simulations.     

High Velocity Impact of Glass-Reinforced Plastic Laminates with Sharp Nose Projectile Experimental Results Versus Some Models Predictions

This study investigates high velocity impact performance of glass-reinforced plastic (GRP) laminates struck by sharp nose conical projectiles and compares the experimental results with some available predicting models. Five models were selected for assessment. Close correlation was obtained between predicted ballistic limit velocities from the models, which incorporated projectile nose geometry with that of experimental results. Considerable scatter was observed for the other models. Projectile deviation from normal impact during perforation was the reason for this discrepancy. Successful modification was made to one of the models using residual velocity results from a high velocity impact test instead of quasi-static results.     

高速钝头弹侵彻中厚高强聚乙烯纤维增强塑料层合板的机制

根据侵彻过程中的不同受力状态和耗能机制,结合高强聚乙烯纤维增强塑料(UFRP)层合板抗高速侵彻特点,将高速钝头弹对中厚UFRP的侵彻过程分为压缩镦粗、剪切压缩和拉伸变形三个阶段。基于三阶段侵彻机制,利用能量守恒原理建立了钝头弹高速侵彻中厚UFRP的弹道极限和剩余速度计算模型。采用侵彻模型计算了相关文献弹道试验工况下弹体的剩余速度和弹道极限速度,计算值与文献试验值吻合较好。三阶段侵彻模型考虑了试验中出现的纤维熔断和弹体镦粗现象,能够对高速钝头弹侵彻中厚UFRP的剩余速度和弹道极限速度进行合理预测,具有一定的理论价值和工程应用价值。     

Finite element calculation of 4-step 3-dimensional braided composite under ballistic perforation

The ballistic perforation test results of 4-step 3-dimensional (3D) braided Twaron^®/epoxy composites, which were subjected to impact by conically cylindrical steel projectile, are presented. The residual velocities of projectile perforated composites target at various strike velocities were measured and also compared with that from finite element calculation. ‘Fiber inclination model’ for 3D textile composites was adopted to decompose the 3D braided composite at quasi-microstructure level for the geometrical modeling in preprocessor of FEM. The material modeling was also based on this simplified model. The finite element code of Ls-Dyna was used to simulate the impact interaction between projectile and inclined lamina. The residual velocity of projectile perforating the entire 3D braided composite can be calculated from the sum of kinetic energy loss of the projectile that obtained from FEM. From the simulation of ballistic penetration process and comparison between numerical results and experimental results, it proves that the analysis scheme of quasi-microstructure level in this paper is valid and reasonable. The simplified method in this paper could be extended to model other kinds of 3D textile composites under ballistic impact.     

Perforation experiments on HY-100 steel plates with 4340 Rc 38 and maraging T-250 steel rod projectiles

We conducted perforation experiments with 4340 R_c 38 and maraging T-250 steel, long rod projectiles and HY-100 steel target plates at striking velocities between 80 and 370 m/s. Flat-end rod projectiles with lengths of 89 and 282 mm were machined to nominally 30-mm-diameter so they could be launched from a 30-mm-powder gun without sabots. The target plates were rigidly clamped at a 305-mm-diameter and had nominal thicknesses of 5.3 and 10.5 mm. Four sets of experiments were conducted to show the effects of rod length and plate thickness on the measured ballistic limit and residual velocities. In addition to measuring striking and residual projectile velocities, we obtained framing camera data on the back surfaces of several plates that showed clearly the plate deformation and plug ejection process.     

The effect of hybridization on the ballistic impact behavior of hybrid composite armors

In the present study, effect of hybridization on the hybrid composite armors under ballistic impact is investigated using hydrocode simulations. The hybrid composite armor is constructed using various combinations and stacking sequences of fiber reinforced composites having woven form of fibers specifically high specific-modulus/high specific-strength Kevlar fiber (KF), tough, high strain-to-failure fiber Glass fiber (GF) and high strength/high stiffness Carbon fiber (CF). Different combinations of composite armors studied are KF layer in GF laminate, GF layer in KF laminate, KF layer in CF laminate and CF layer in KF laminate at various positions of hybridized layers for a fixed thickness of the target. In this article the results obtained from the finite element model are validated for the case of KF layer in a GF laminate with experimental predictions reported in the literature in terms of energy absorption and residual velocity and good agreement is observed. Further, the effect of stacking sequence, projectile geometry and target thickness on the ballistic limit velocity, energy absorbed by the target and the residual velocity are presented for different combinations of hybrid composite armors. The simulations show that, at a fixed thickness of the hybrid composite armor, stacking sequence of hybridized layer shows significant effect on the ballistic performance. The results also indicate energy absorption and ballistic limit velocity are sensitive to projectile geometry. Specifically, it is found that arranging the KF layer at the rear side, GF layer in the exterior and CF layer on the front side offers good ballistic impact resistance. The hybrid composite armor consisting of a CF layer in KF laminate acquires maximum impact resistance and is the best choice for the design compared to that of other combinations studied.     

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.     

Influence of fiber orientation and thickness on the response of glass/epoxy composites subjected to impact loading

Composite laminates, made of glass/epoxy using compression molding technique, were subjected to impact loading. The ballistic limit and energy absorption capacity of the laminates were obtained. Experiments were carried out to study the effect of fiber orientation and thicknesses on ballistic limit and energy absorption of the laminates, by using a rigid conical bullet having 9.5 mm diameter and mass of 7.5 g in an air gun. Analytical expressions were obtained to find the ballistic limit, residual velocity and energy absorption capacity of the laminates. The expressions obtained by considering the various damage modes, which were involved in penetration, when laminates subjected to impact loading. The values obtained from analysis were compared with experimental results and good agreement was found. The strain rate sensitivity of the glass/epoxy composites was considered for analysis.     

Yawing impact on thin plates by blunt projectiles

Two experimental investigations and a corresponding analytical study were conducted to examine the phenomena attendant to the impact of blunt-nosed, hard-steel strikers on stationary thin plates of aluminum and steel at moderate angles of yaw and zero obliquity. The variation of ballistic limit with yaw angle or the terminal velocity and final trajectory angle in perforation tests were ascertained. Post-mortem examination of the plates indicated that damage and failure occurred by bulging, lateral indentation, and side and front petaling. A theoretical model based on a membrane representation was developed that analyzed the impact by dividing the process into five stages. This model underpredicted the ballistic limit by up to 14%, with better correlation found at higher yaw angles. Excellent agreement was observed between the experimental and analytical final velocities when the data points were corrected to reflect the difference between the experimental values of the ballistic limit and that predicted by the model. Fair agreement was found between the experimental and the analytical values of the trajectory angle.     

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.     

三维编织复合材料弹道侵彻准细观层次有限元计算

三维编织复合材料相比于层合复合材料有较高的层间剪切强度和断裂韧性,因而具有更高的冲击损伤容限。用钢芯弹对三维编织复合材料作弹道贯穿测试,得到弹体的入射速度和剩余速度,并考察侵彻破坏模式。目前对三维编织复合材料弹道侵彻性能计算主要建立在连续介质假设上,从真实细观结构计算三维编织复合材料弹道冲击性能尚有一定难度,用三维结构复合材料的纤维倾斜模型在准细观结构层次上分解三维编织复合材料,就其中的一块倾斜单向板作弹道侵彻有限元计算,由弹体动能损失得到贯穿整个复合材料靶体后弹体的剩余速度。有限元计算及与弹道测试结果的比较证明在准细观层次上计算三维编织复合材料弹道冲击性能的有效性。