• Duplan, Yannick

Abstract

Bilayer armour configurations are designed to defeat Armour-Piercing (AP) projectiles. They consist of a ceramic front plate that aims to shatter and break the impacting threat. Due to its brittleness, the ceramic is combined with a ductile backing plate such as composite for the conversion of debris’ kinetic energy into deformation and delamination [1]. One of the most common testing techniques to evaluate the ballistic performances of ceramics is the ballistic limit velocity test called V50: a projectile is launched onto the ceramic backed with an aluminium alloy or a steel alloy. Using a NATO (North Atlantic Treaty Organization) standard, the probability curve of perforation allows reading the velocity V50 at which the projectile has 50% of probability of perforating the armour [2,3]. During such an impact, the ceramic undergoes three loading stages: (1) triaxial compression, (2) tensile cracking and (3) penetration [1]. In parallel, the AP projectile flows and erodes until capture or full penetration [4]. The penetration process depends on the mechanical strength and damage involved in each stage, making the numerical modelling of such interaction particularly challenging. A series of numerical simulations of V50 test were carried out with Abaqus finite-element code considering the following models: the Johnson-Cook (JC) hardening and damage models [5] is used for the steel-core of an AP projectile, the Johnson-Holmquist-2 (JH-2) model [6] that incorporates a pressure-dependent strength that is considered for representing the mechanical response of the ceramic. In addition, the Denoual-Forquin-Hild (DFH) anisotropic damage model [7,8] is used to simulate the tensile damage generated in the ceramic. The numerical results provide a better understanding of the damage modes induced in the projectile and in the target during the ballistic impact.1. Gooch, W.A., Jr. Ceramic Armor Development - An Overview of Ceramic Armor Applications. In Ceramic armor materials by design; McCauley, J.W., Ed.; Ceramic transactions; The American Ceramic Society: Westerville, Ohio, 2002; pp. 3–23 ISBN 978-1-57498-148-3. 2. Normandia, M.; Gooch, W.A., Jr. Penetration and Ballistic Testing - An Overview of Ballistic Testing Methods of Ceramic Materials. In Ceramic armor materials by design; McCauley, J.W., Ed.; Ceramic transactions; The American Ceramic Society: Westerville, Ohio, 2002; pp. 3–23 ISBN 978-1-57498-148-3. 3. Johnson, T.; Freeman, L.; Hester, J.; Bell, J. Ballistic Resistance Testing Techniques - IDA (Institute for Defense Analyses) Research Notes. 4. Normandia, M.; Lasalvia, J.; Gooch, W.; McCauley, J.W.; Rajendran, A.M. Protecting the Future Force: Ceramics Research Leads to Improved Armor Performance. AMMTIAC 2004, 8. 5. Johnson, G.R.; Cook, W.H. Fracture characteristics of three metals subjected to various strains, strain rates, temperatures and pressures. Eng. Fract. Mech. 1985, 21, 31–48. 6. Johnson, G.R.; Holmquist, T.J. An improved computational constitutive model for brittle materials. In Proceedings of the AIP Conference Proceedings; AIP: Colorado Springs, Colorado (USA), 1994; Vol. 309, pp. 981–984. 7. Denoual, C.; Hild, F. A Damage Model for the Dynamic Fragmentation of Brittle Solids. Comput. Methods Appl. Mech. Eng. 2000, 247–258. 8. Forquin, P.; Hild, F. A probabilistic damage model of the dynamic fragmentation process in brittle materials. Adv. Appl. Mech. 2010, 44, 1–72.

Topics

• impedance spectroscopy
• simulation
• aluminium
• strength
• anisotropic
• steel
• aluminium alloy
• composite
• ceramic