Experimental study on the penetration effect of ceramics composite projectile on ceramic/A3 steel compound targets

Di-qi Hu,Jin-ru Wng,Li-kui Yin,Zhi-gng Chen,Rong-cheng Yi,Cheng-hu Lu

aNational Defense Key Laboratory of Underground Damage Technology,North University of China,Taiyuan 030051,China

bChangzhou Sanyou Sissan Protective Materials MFG Co.,Ltd,Changzhou 213100,China

Experimental study on the penetration effect of ceramics composite projectile on ceramic/A3 steel compound targets

Di-qi Hua,*,Jian-ru Wanga,Li-kui Yina,Zhi-gang Chena,Rong-cheng Yia,Cheng-hua Lub

aNational Defense Key Laboratory of Underground Damage Technology,North University of China,Taiyuan 030051,China

bChangzhou Sanyou Sissan Protective Materials MFG Co.,Ltd,Changzhou 213100,China

A R T I C L E I N F O

Article history:

9 May 2017

Accepted 22 May 2017

Available online 26 May 2017

Projectile

Penetration

Ceramic

Impact dynamics theory

Numerical simulation

In order to improve the penetration of projectiles into ceramic composite armors,the nose of 30 mm standard projectile was replaced by a toughened ceramic nose,and the performance of ceramic-nose projectiles penetrating into ceramic/A3 steel composite targets has been experimentally researched. According to impact dynamics theory,,the performances of 30 mm ceramic-nose projectile and 30 mm standard projectile penetrating into the ceramic/A3 steel composite targets were analyzed and compared using DOP method,especially focusing on the effects made by different nose structures and materials. The aperture and depth of perforation of projectile into the armor plates as well as the residual mass of bullet core under the same conditions were comparatively analyzed.A numerical simulation was built and computed by ANSYS/LS-DYNA.Based on the simulated results,the penetration performance was further analyzed in terms of the residual mass of bullet core.The results show that the ceramic nose has a great effect on the protection of bullet core.

?2017 The Authors.Published by Elsevier Ltd.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

1.Introduction

The protective performance of armored vehicles has been constantly improved with the development of technology.Most of their protective materials are still metallic.Metallic materials are good in strength and processability,enabling their wide use in equipment for damage or protection.Even for antipersonnel warhead,the metallic material and its alloy are the main materials. However,this kind of general material reaches a bottleneck in the improvementofpenetration performance ofantipersonnel warhead.

Nicholas et al.[1]put forward the method of adding pre-stress to control the damage of ceramic projectile during the armor piercing,and designed several polycrystalline diamond projectile noses with different masses to penetrate the concrete targets.The result shows the armor-piercing depth gets deeper with the increase in diamond mass.And at the touching velocity increasing from 1 km/s to 2 km/s,the diamond projectile gets deeper while standard steel standard projectile gets shallower.LI Shoucang et al. [2]did a comparative research on the penetration of ceramic and alloy steel cylindrical structures into ceramic/composite targets, and indicated that the ceramic structure created much heavier damage to targets than the alloy steel one.FU Jianping et al.[3] compared the penetration performances of ceramic and standard steel projectiles, finding that the ceramic projectile is superior to steel projectile in the penetration performance.

Ceramic materials,due to the characteristics of high hardness, heat-resistance and pressure-resistance,are adopted for the nose of 30 mm projectile in thepaper.And the armor-piercingperformance of ceramic-nose projectile was experimentally researched by comparing to the standard projectile.

2.Material characteristics

The moment when the high-hardness brittle ceramic plate[4] was penetrated by the projectile,stress concentrate occurred on the contact surface,and the huge compressive load made the ceramic on the contact surface broken into pieces[5].The ceramic pieces moved against the projectile in the opposite direction, putting too much friction drag on the projectile.When the compressive stress spread along the axial direction,an axial crack was formed on the ceramic plate,forming a ceramic cone[6].Underthe drive of projectile,the ceramic cone continued to work on the metal plate,enlarging the contact area which is conductive to the spread and absorption of impact energy by metal plate.And the metal plate is a support to the ceramic plate,protecting the ceramic against soon breakage so as to fully play its anti-bullet performance.In the process of deeper penetration,a lot of ceramic pieces are generated,which leads to the abrasion and blunting of projectile nose,of which mass and velocity are reduced during the process,and thus the penetration performance is sharply reduced.

The material of ceramic-nose used in the paper is Al2O3ceramic after improvement.By adding proper proportional ZrO2 to Al2O3ceramic,the density of Al2O3is improved.And then adding the mixed liquid of dispersant and monomer solvent during ballmilling,and then adding catalyst and initiator,all these after well mixing are injected into a shaped mould.Then an improved Al2O3ceramic will be shaped.After natural drying and then machining operation according to the required size,the improved Al2O3ceramic is sintered at 1400°C for about 40 h.After all these processes,the improved Al2O3ceramic is eventually shaped and to be used for the ceramic-nose of projectile.

Compared to common ceramic,this toughened ceramic material is more uniform in particle distribution and tightly integrates between particles,with bending strength of 850 MPa and fracture toughness of 9.35 MPa/m2.And it is also featured with highmelting-point,high pressure resistance,wear-corrosion resistance,high tenacity and low cost.The toughened ceramic nose of projectile is as shown in Fig.1.

3.Test design

3.1.Test projectiles

The 30 mm standard armor-piercing discarding sabotprojectiles and ceramics composite projectiles(see Fig.2)were used in the test,whose shape and mass are basically the same.The ceramic composite projectile mainly consists of ceramic composite nose, projectile core,sabot and bottom bracket,etc.

3.2.Test targets

The test target is the ceramic/A3 steel composite target whose structure from the front side to the back side successively is glass fiber layer,ceramic,glass fiber layer and five-layer A3 steel plates. The glass fiber layer acts as a buffer layer to prevent against the collapse of ceramic debris and attenuate the stress waves.The ceramic plate acts as a barrier layer,due to its high compressive strength and high hardness,severe erosion,fracture and de flection happen in projectile when hitting the ceramic plate,thus affecting the subsequent penetration process.The steel plates provide good support for the ceramic plate.

Fig.1.Toughened ceramic nose of projectile.

Fig.2.Ceramic composite projectile for test.

The ceramic plate,of which thickness is 15 mm,consists of glass fiber layer,alumina ceramic piece and glass fiber layer which are bound together and their average density is 3.7×103kg/m3.The steel plates,with the thickness of 20 mm per piece,were made of Q235 steel.The size of the ceramic/A3 steel composite target(see Fig. 3) is 200 mm × 200 mm × 115 mm (width×height×thickness).

4.Analysis of test results

The standard projectile and the ceramic composite projectile penetrated the ceramic/A3 steel composite target vertically at the velocityof 870 m/s and 851 m/s,and damagedthe targets,as shown in Fig.4(left:the targets hit by ceramics composite projectiles; right:the targets hit by standard projectiles).

Fig.3.Ceramic/A3 steel composite target.

Fig.4.Photographs of damaged targets.

During the course of penetration,the aluminous projectile ogive was soon eroded,and the projectile core directly acting on the ceramic plate was exposed,which led to the axial cracks in it and the formation of a ceramic cone.Under the push of projectile,the ceramic cone continued to work on the steel plate,which spread and absorbed the impact energy.The steel plate also gave support to the ceramic plate,protecting the ceramic against soon breakage which fully played its anti-projectile performance.During the process,the ceramic plate played a great role in the erosion of projectile core,causing the de flection of projectile(see Fig.4(b)) which severely affected the continuous penetration of projectile into the steel plate.

Due to its high strength and high hardness,the ceramic-nose projectilegenerated tremendouscompression stresson the ceramic plate on the moment of hitting,and at the same time the ceramics nose was crushed;the pressure wave on the ceramic plate was re flected by the ceramic-steel contact surface to form an unloading wave[8],which causes some crack and collapse of ceramic plate.The projectile core was able to continue to penetrate the steel platewhile remaining intact.It could be seen fromFig.4(a) that the crack of ceramic-plate fibrous layer created by ceramics composite projectile was obvious,while a perforation was created by the standard projectile.

Fig.5 shows the residual projectile cores collected after test (left:ceramic composite projectile core;right:standard projectile core).It can be seen from Fig.5 that both the projectile cores are integrated without pieces and their topswere deformed tobe coneshape.But the top functional area of ceramic composite projectile core is smaller than that of the standard projectile core.And the length ratios(the length of projectile core before penetration is divided by the residual length of projectile core after penetration): ceramic composite projectile core and standard projectile core are 66.32%and 59.07%,respectively.The mass ratios(the mass of projectile cores before penetration is divided by the residual mass of projectile cores after penetration):ceramic composite projectile core and standard projectile core are 71.32%and 59.07%,respectively.All these showthat the ceramic-nose structure plays a part in protecting the projectile core against erosion during penetration and maintaining a relatively longer projectile core cylinder which improves the penetration performance of projectile in a real way.

From Table 1,we can see that although the velocity of standard projectile is a little faster,the crater on target created by ceramics composite projectile is deeper,and the damaging area on steel plate is obviously larger while the standard projectile has no obvious damage to the 5th layer steel plate(Fig.4(f)right).It is clear that ceramic composite projectile is superior to standard projectile in damage effect on targets.

5.Theoretical calculation of impact pressure

The pressure value of shock wave created by projectiles was analyzed and theoreticallycalculated.The Hugoniot formula for the velocity of shock wave and particles behind wave front is

whereDis the velocity of shock wave;uis the velocity of particles behind wave front;a&bare the Hugoniot parameters of the materials[9,10](see Table 2).

According to the momentum conservation law and continuous conditions on the interface,the moment whenprojectile hits on the ceramic plate,the pressureat a hit point can be explained as follows [11-13]

where the subscriptpis denoted as the projectile;the subscript is denoted as the target:panduare the impact pressure and particle

Fig.5.Projectile cores after penetration.

Table 1 Data of targets after damage.

Table 2 Hugoniot parameters of the materials.

velocity,respectively.The real velocity at the impact interface is

Where v0is the striking velocity of projectiles.

It is concluded from Eqs(3)and(4)that

where

The pressure generated on ceramic plate hit by projectiles can be calculated from Eqs.(2),(3)and(6).

Fig.6.Finite element model.

Table 3 Material parameters of standard projectile.

Table 4 Ceramics material parameters.

In the numerical calculation,the instant impact pressure on ceramic/A3 steel composite armor target applied by ceramic composite projectile is 1.3 GPa higher than that applied by the standard projectile at the velocityof 850 m/s,and the damage effect of ceramic composite projectile is also better than that of standard projectile.

6.Finite element simulation and result analysis

6.1.Material model and parameters

A finite element model was established to improve the computational ef ficiency.The central part penetrated by projectiles was processed.Fig.6 shows the projectile and target plate units under meshing.

For the models used in calculation,the J-C(MAT_JOHNSON_-COOK)model(see material parameter in Table 3)is adopted to describe projectile cores under Gruneisen equation of state;the JC2 (MAT_JOHNSON_HOLMQUIST_CERAMICS)modelisused for ceramic plate(see the material parameters in Table 4).The Plastic-Kinematic model is used for metal back plates.Surface-to-surfaceerosion contact algorithm (CONTACT_ERODING_SURFACE_TO_SURFACE)is adopted to show the interaction between projectile and target plates.The surface-tosurface free contact algorithm (CONTACT_AUTOMATIC_SURFACE_TO_SURFACE)is adopted to show the interaction between projectile nose and projectile core.

Fig.7.The moment when projectile nose contacts with target.

Fig.8.The moment when projectile core contacts with target.

6.2.Numerical simulation analysis

Thenumericalsimulation ofprojectilespenetratinginto ceramic/A3 steel target at the velocity of 850 m/s was made under the dynamic analysis software LS-DYNA.And the comparisons of the two projectiles penetrating into the multi-layer A3 target are shown in Figs.7-10,where ceramics composite projectile is on the left,and standard projectile is on the right.

Fig.11 shows the mass-time curves showing how the residual mass of projectile cores change with time,whereinmstands for the residual mass of projectile core,tstands for the projectile-target action time.Fig.12shows the acceleration-time curves showing the acceleration of projectile core changing with the time,whereinastands for the acceleration of projectile core,tstands for the projectile-target action time.

It can be seen from Fig.7,at the moment when projectiles hit target,the stress on the target produced by ceramics composite projectile is obviously greater than that by standard projectile,and during the process,the nose of standard projectile was eroded rapidly.As shown in Fig.8,no great damage happened to the target plates during penetration of standard projectile,while ceramics composite projectile almost penetrated through the whole ceramic plate.From Fig.9,it can be seen that during the subsequent penetration,the inclination of standard projectile core is more noticeable than that of ceramic-nose projectile.For the damageeffect on targets(see Fig.10),the ceramics composite projectile penetrated through the first layer of A3 steel plate,and greatly damaged the second layer of A3 steel plate,while the standard projectile failed topenetratethrough the first layerof A3 steelplate. It can be seen from the acceleration-time curves(Fig.11)that the standard projectile core bears much greater load than that for ceramics projectile core.During this process,the ceramics nose provided good protection for its projectile core sothat its eroded part is much less and capable of maintaining more complete shape than that of the standard projectile,and ceramics composite projectile core bears less load than that of standard projectile during the subsequent penetration.It can be seen from the projectile core mass-time curves(Fig.12)that the residual mass ratios of the projectile cores are 69.3%(ceramic projectile)and 64.1%(standard projectile),respectively,and the test results are very close.

Fig.9.Penetration processes of projectile cores.

Fig.10.Damaging effects of target plates.

Fig.11.Acceleration-time curves.

Fig.12.Mass-time curves of projectile core.

7.Conclusions

Through the experimental study on penetration performance of ceramics composite projectile,it can be concluded that:

1)The test results are basically the same as the numerically simulated results.

2)The penetration performance of ceramic-nose projectile is better.The ceramic-nose projectile applies a greater impact pressure on targets while the standard projectile causes no much damage to targets and its great de flection happens during penetration.

3)The ceramic-nose structure plays a role in protecting the projectile core against erosion during the penetration process so as to maintain a relatively longer core cylinder body,which improves the penetration power of projectile core in a real way.

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11 January 2017

*Corresponding author.National Defense Key Laboratory of Underground Damage Technology,North University of China,3 Xueyuan Road,Taiyuan City 030051,Shanxi,China.

E-mail address:251876971@qq.com(D.-q.Hu).

Peer review under responsibility of China Ordnance Society.

http://dx.doi.org/10.1016/j.dt.2017.05.011

2214-9147/?2017 The Authors.Published by Elsevier Ltd.This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).

in revised form