About ballistic protection structure behaviour under impact.

Slamnoiu, Georgica ; Bejan, Mihai ; Vladu, Gabriel 等

1. INTRODUCTION

Presently, there is a special interest in estimation of effect at impact between a projectile and different protection structures (Nastasescu, 2001).

Actual numerical simulation trend does not exclude experimental validations which provide accurate results (Goga et al., 2007).

The paper presents a ballistic structure system behavior under impact. The structure system consists, in order of impact, in an armored plate and a personnel bulletproof jacket.

The armored plate is a high strength steel shell. It is the first line of defense again projectile intrusion.

The bulletproof jacket has 33 Kevlar layers and one layer of multiple ceramic plates.

Three types of projectiles are used to study the impact with armored shell and bulletproof jacket when the first one is penetrated.

2. EXPERIMENTAL TESTS

The first approach was experimental.

The experimental stand scheme is reveled in figure 1.

The projectile is thrown out of the barrel and hits the armored plate. The armored plate is a 500 x 500 mm embedded shell. It is placed at 50 m from the barrel.

We are interested to reveal also the bulletproof jacket behavior so the projectile completely penetrates the armored plate in all studied cases.

The bulletproof jacket is placed at 300 mm behind the armored plate. It consists of Kevlar and ceramic plates (Hadar et al., 2006).

[FIGURE 1 OMITTED]

The ceramic plates are placed in front of Kevlar in 5 columns and 6 rows. Each individual plate is 50 x 50 x 10 mm.

Three types of projectiles are used: 7.62 mm, 12.7 mm and 14.5 mm caliber.

In all cases the armored plate is completely penetrated and the projectile hits the bulletproof jacket reinforced with ceramic plates.

3. EXPERIMENTAL RESULTS

The lunch system characteristics are presented in table 1.

The technical data of the projectiles are presented in table 2.

Penetration of armored plate with 12.7 mm projectile is revealed in figure 2.

We can see the complete penetration of the armored plate. This reduces the kinetic energy of the projectile. The residual energy after first impact determines the behavior with bulletproof jacket impact, depending on the projectile type and launching conditions (mass, initial speed).

Experiments revealed that the armored plate is efficient for projectiles with 7.62 mm caliber. As the caliber grows, the kinetic energy increases also. This requires augmenting the armored plate in order to slow down the projectile enough so it will not penetrate the bulletproof jacket.

The behavior of the bulletproof jacket is presented in table 3.

[FIGURE 2 OMITTED]

4. NUMERICAL MODEL

This impact phenomenon is a complex one. For this reason was also realized a numerical simulation. It models only a part of the experiment--armored plate penetration. This simulation can be considered a starting point for further development (Chirica, 2001;Bucur & Ionescu, 2008).

The numerical model reveals the most important sequences in penetration of armored plate figure 3.

At initial moment, t = 0 us, the armored plate is intact and the projectile has the speed determined from ballistic flying on the 50 m trajectory.

The second revealed moment, t= 0.35 us, the projectile get into contact with the armored plate. This is considered to be the last moment when these two elements have the original shape.

Att = 2.4 us can be observed the start of the plastic transformation of the projectile tip and a slightly modification of the armored plate.

In the fourth moment, presented in figure 3 (t = 3.2 us), the modification of the armored plate continues caused by increasing stiffness of the projectile tip - produced by plastic flow.

After t = 4.0 us the armored plate is penetrated almost completely and its structure is modified.

At t = 5.5 us moment the armored plate is completely penetrated and the front side shape of the projectile is new. The kinetic energy of the projectile is significantly lower after penetration.

5. CONCLUSIONS

The study of a high speed projectile impact is very important in personal protection structures design and destination.

The study reveals a quality and a quantity behavior of a bulletproof jacket.

A highly importance of ceramic plate is reveled. In some cases it stopped the projectile to penetrate and in other cases produces the ricochet.

The safety degree level is accurate determined and indicates the limits in use of a bulletproof jacket.

Numerical model reveals the most important moments impossible to reveal by experiment.

[FIGURE 3 OMITTED]

We intend to build a complex numerical model as further research. It is always recommended that some numerical models to be validated by experiments.

6. REFERENCES

Bucur, P. & Ionescu, C. (2008). Numerical results analysis of piercing incendiary bullets firings regarding configuration constituted of armored skin and ballistic protection equipment, The 3th International conference "Advanced Concepts in Mechanical Engineering", Bul.Inst.Polit.Iasi, ISSN 1011-2855, Iasi, June 2008, Iasi Polytechnic Publishing House, Iasi, Romania

Chirica, I. (2001). Finite Element Analysis in Structural Engineering, "Down Danube" University Foundation Publishing House, 973-8139-50-3, Galati

Goga, D.; Tiganescu, V.; Chereches, T. & Carmaci, M. (2007). Some aspects regarding testing procedures for 9x19 mm ammunition system while evaluating ballistic and safety characteristics during life cycle, Proceedings of the 6th WSEAS International Conference on System Science and Simulation in Engineering, Published by WSEAS Press, pp. 168 - 172. ISBN 978-960-6766-14-5 Venice, Italy, nov., 2007

Hadar, A., Bordeasu, I., Mitelea, I. & Vlasceanu, D. (2006). Experimental Validation of a Theoretical Model Used for Analysis of the Laminate Composite Structures, Plastic Materials 43 (1), Bucharest, 2006, pp 70-73. ISSN 0025-5289

Nastasescu, V. (2001). Upon Material Constants in Dynamic Analysis Applied at Impact Problems, Proceedings of XXIX Scientific Communication Session Modern Technologies in XXI Century, Russu, M., Section 14, Bucharest, November 2001, Military Technical Academy, Bucharest

Tab. 1. Characteristics of the lunch system

 Ballistic barrel Ballistic barrel
Lunch system Barinov Levasov M.T.B.

Barrel length 755 mm 1.005 mm 1,276 mm
Total length 900 mm 1.200 mm 1,480 mm
Caliber 7.62 mm 12.7 mm 14.5 mm

Tab. 2. Characteristics of the projectiles

Projectiles 7.62 x 54 mm 12.7 x 108 mm 14.5 x 114 mm

Velocity at 830 m/s 820 m/s 945 m/s
barrel muzzle

Energy at barrel 337 kgf m 1520 kgfm 2.910 kgf m
muzzle

Bullet mass 9.6 g 51 g 64 g

Bullet Core Steel Steel Steel

Powder charge 3.00-3.30 16.00-17.00 31.00-33.00
mass

Tab. 3. Bulletproof jacket behavior

Projectile 7.62 x 54 mm 12.7 x 108 mm

Component Ceramic Kevlar Ceramic Kevlar

Qualitative Amprented Partial Amprented Partial
Results penetration penetration

Observations -- Failure -- Failure of
 of 11 21
 layers layers

Protection 50% 84% 50% 36,4 %
degree on
components

Protection 67% 43,2%
degree of
assemble

Projectile 14.5 x 114 mm

Component Ceramic Kevlar

Qualitative Complete Complete
Results penetration penetration

Observations Failure of
 33
 layers

Protection 0% 0%
degree on
components

Protection 0%
degree of
assemble