International Journal of Machine Tools and Manufacture
Analysis and investigation of ballistic impact on ceramic/metal composite armour
Introduction
Generally, impact problems were primarily of concern to the military, either for defenseive or offensive purposes to develop armour or ammunition. Nowadays, civilian applications demand extreme safety of the products, therefore, it is essential to understand the material behaviour under intense short duration or impact loadings [1]. Needless to say, using metallic armour for personal protection is extremely heavy and would not be popular. On the other hand, reinforced fiber composites have been used for these purposes, but have been shown to be very susceptible to impact damage, thus limiting their usefulness for such an application [2], [3], [4]. It is essential therefore that armour be as light as posssible for military operations requiring high manoeuvrability.
Certain high hardness ceramics combined with their low density offer the possibility of reducing the weight per unit area required for given protection. Needless to say, in these cases ceramic armour emerges as a rigid covering, capable of reducing the mass and the impact velocity of the projectile, causing it to disintegrate into small fragments which could easily be absorbed by the flexible base which supports the ceramic layer. The dynamic load of projectile impact on a target involves complex mechanism of penetration and perforation, thus making it necessary to introduce many simplifying assumptions to the problem. For such reasons, many experimental tests of different conditions of design, material, type of projectile and others are needed.
In the present work, several tests have been conducted at various impact velocities of projectiles and energy levels to characterize the projectile impact behaviour on ceramic–metal composites.
Section snippets
Simplified theoretical analysis
The mechanics of perforation of projectiles on metallic plates has already been analysed theoretically by many authors [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]. These types of analyses lead to the determination of the required impact perforation energy and the residual strength. In the present study, the armour of composite material is made of two different materials having different properties, and they perform in a complementary manner during the process of perforation of the
Experimental data and procedure
All the specimens were tested ballistically according to the MIL-STD-662E Standards [18], [19], [20]. The same projectile calibre was used throughout the whole experimental tests being 7.62×51 mm, and its initial velocity is approximately 835 m/s and 9.54 g, as shown in Fig. 6. The stainless steel 304 had the following dimensions 30×30×1.5 cm over a ceramic base plate plate of 5×5 cm having different thicknesses of 7.3, 9.3 and 11.3 mm. In addition, a
Comparison between theoretical and experimental results
Normally, the kinetic energy is dissipated in eroding the impacting end when the conical-ended projectile of mass (Mp) impinges at normal bullet speed (Vi(t)). This fact causes a reduction in the speed before it can begin the penetration process of the ceramic plate. The impact of the projectile causes a concentrated zone of intense stress, thus forming a coronet fracture zone around the penetrating projectile Fig. 1.
Both the maximum deflection and the residual projectile mass were calculated
Conclusions
The development of a simple and reliable theory to predict the loss of the ballistic impact energy absorbed by the armour plate was the main objective of the present work. It can also be concluded, despite the approximate nature of the analysis presented, that there is good agreement between the experimental and the theoretical results. In addition, the experimental results reported here demonstrate that composite ceramic–metal compete well with conventional materials.
The main advantage of the
Acknowledgements
The authors wish to thank CTA and UFSC-LabMat for the use of the facilities and CAPES and CNPq for partially financing the project.
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