PSI - Issue 71

Nikhil Andraskar et al. / Procedia Structural Integrity 71 (2025) 158–163

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backed by aluminum. Utilizing finite element simulations to analyze different performance metrics, the research reveals that alumina/steel configurations are more effective against tungsten projectile impacts for the same thickness. Conversely, alumina/aluminum configurations show superior performance against steel projectile impacts when factoring in areal density. The study by Rashed et al. (2016) conducts a numerical investigation of multi-layered ceramic armors, emphasizing the function of alumina ceramic tiles and polymeric interlayers. The findings indicate that an armor configuration featuring thin front ceramic tiles supported by thicker tiles, especially when using polystyrene interlayers, exhibits enhanced ballistic performance against armor-piercing (AP) projectiles. Understanding the damage mechanisms and stress responses of alumina material is essential for conducting impact studies on monolithic alumina plates. Shin et al. (2005) outlines a bar impact test conducted at low velocity to examine the damage progression in alumina plates under quasi-static conditions. The research reveals that the application of pre-stress in the direction of the impact affects the fracture behavior, with greater pre-stress resulting in reduced damage by minimizing radial cracks due to enhanced apparent stiffness. Toussaint and Polyzois (2019) used finite element simulations to evaluate damage in composite-backed ceramic tiles, validating these simulations through impact experiments on alumina ceramic tiles. The research investigates various constitutive material models to simulate brittle fracture and examines their effectiveness in representing damage mechanisms. while Shin et al. (2005) propose that pre-stress can mitigate damage, Rahbek et al. (2019) suggest that a composite cover may actually exacerbate damage due to its restraining effects. This contradiction underscores the intricate nature of damage behavior in alumina plates and the impact of external factors on their fracture mechanisms. Fragment-simulating projectiles (FSPs) are specifically designed to mimic the behavior of shrapnel or fragments generated by explosive devices, which are common hazards in military conflicts. FSPs are used in testing to evaluate how well different materials and structures can protect against these threats. Their significance lies in providing a standardized method for assessing and comparing the ballistic resistance of various materials, enabling the development of protective solutions that help safeguard lives and equipment in combat situations Z. Guo (2019), Fras (2015). The ballistic performance of fragment-simulating projectiles (FSPs) is influenced by the material and thickness of the target, as well as the projectile's velocity and shape. For example, the aluminum alloy AA7020-T651 shows a transition in failure modes from plugging to discing as impact velocities increase, a behavior that has been numerically modeled using the Lagrangian method Fras et al. (2015). Additionally, data on ballistic-limit velocities for different aluminum alloys and plate thicknesses have been provided, along with an equation that predicts the ballistic-limit velocity for FSPs that penetrate aluminum armor plates. The ballistic limit velocity is a crucial parameter, as it indicates the point at which a projectile can penetrate a target. The Finite Element Method (FEM) has been widely utilized to model the ballistic performance of fragment-simulating projectiles (FSPs) striking various materials. For example, Fras et al. (2015) detail the use of LS-DYNA software to simulate the plugging failure mode in aluminum alloy AA7020-T651 plates when impacted by FSPs. This study compares FEM results with those obtained from Smoothed Particle Hydrodynamics (SPH), ensuring that the target deformation geometry aligns with experimental data. Similarly, Minh et al. (2014) use a multi-scale FEM model to predict the impact behavior of multi-layer plain woven fabrics against FSPs, showing strong agreement with experimental results. Haque et al. (2012) further apply FEM to simulate multi-hit ballistic impacts on composite laminates using LS-DYNA, achieving good correlation with experimental ballistic limit velocities and offering insights into damage progression. Impact studies on monolithic alumina plates demonstrate that damage mechanisms are affected by pre-stress and external covers, where pre-stress may help reduce damage while external covers could lead to increased damage. These results highlight the necessity of taking multiple factors into account when designing and utilizing alumina plates in scenarios where impact resistance is essential. This study focuses on studying the ballistic performance of monolithic alumina plates against fragment-simulating projectiles. There is hardly any study on the ballistic performance of alumina against fragment simulating projectile in the available literature. Finite element analysis is aided by ANSYS/LSDYNA code. Moreover, the numerical model is further explored to study the damage mechanism in the alumina plate at different impact velocities of the fragment-simulating projectile. 2. Constitutive modelling For material to show realistic behavior during the numerical simulation, constitutive modeling of the material has a big role to play. During this study, to explore the material response of alumina ceramic, the Johnson-Holmquist (JH-2) material model is used. This model is generally used for exploring the response of brittle materials under high strain rate conditions such as impacts and explosions. For projectile material, the Johnson-Cook (JC) model is preferred. This model is suitable for metals at high strain rates. 2.1 JH-2 material model