Lightweight armours made of ceramic/composite or ceramic/metal materials have been highly investigated as ballistic protections through analytical and numerical models. Ceramic provides the capability of defeating armour piercing (AP) projectiles eroding projectile tip during the impact, while the composite or metal backing absorbs kinetic energy of the decelerated projectile and catches the ceramic and projectile fragments. Among the previous researchers, no attention was paid to evaluate the ballistic performance of a three-layered armour made of ceramic front face and a mixed composite and metal backing. This thesis presents two new analytical models for the evaluation of the ballistic behavior of three-layered targets. The new models combine the theoretical models of the multilayer ceramic/composite and ceramic/metal armour by introducing new parameters for the interaction between composite and metal plate. Numerical models on three-layer targets have been also performed with LS-DYNA ® software through fully Lagrangian finite-element analysis. The calibration of some parameters such as the erosion strain (FS) for the ceramic material, the Cockcroft-Latham parameter for aluminum alloy and the limit value in tension (SLIMT) for the composite led to achieve results in good agreement with experimental data. The validation of the predictive modelling approaches in terms of residual velocity and ballistic limit is conducted by means of experimental tests. Two specimens made of 8 mm alumina Al2O3, 7 layers Kevlar129 with Phenolic matrix and 2 mm aluminum alloy Al6082 - T6, with different arrangement of the backing, have been used for ballistic impact tests. Tensile tests for the material characterization of composite and aluminum were also performed to obtain input parameters for numerical simulations. The analytical formulations and numerical models result to be in good agreement with experimental data in terms of ballistic curve and damage morphology.
Le armature leggere in ceramico/composito o ceramico/metallico sono state oggetto di studi approfonditi attraverso modelli analitici e numerici. La ceramica ha la capacità di erodere la punta dei proiettili perforanti (AP) durante l'impatto, mentre il supporto in composito assorbe l'energia cinetica del proiettile e cattura i frammenti di ceramica e proiettile eroso. Nella letteratura precedente, nessuna attenzione è stata dedicata alla valutazione delle prestazioni balistiche di un'armatura a tre strati composta da uno strato frontale in ceramica e da un supporto misto di composito e metallo. Questa tesi presenta due nuovi modelli analitici per la valutazione del comportamento balistico di bersagli a tre strati. I nuovi modelli combinano i modelli teorici dell'armatura multistrato ceramica/composito e ceramica/metallo introducendo nuovi parametri per analizzare l'interazione tra il composito e la piastra metallica. Sono stati anche realizzati modelli numerici per protezioni a tre strati con il software LS-DYNA® attraverso l'analisi Lagrangiana ad elementi finiti. La calibrazione di alcuni parametri quali la deformazione per erosione (FS) per il materiale ceramico, il parametro Cockcroft-Latham per la lega di alluminio e il valore limite di tensione (SLIMT) per il composito ha permesso di ottenere risultati vicini ai dati sperimentali. La validazione degli approcci di modellazione predittiva in termini di velocità residua e limite balistico viene condotta mediante prove sperimentali. Per le prove di impatto balistico sono stati utilizzati due provini in Al2O3 da 8 mm, 7 strati di Kevlar129 con matrice fenolica e lega di alluminio da 2 mm 6082 - T6, con diversa disposizione di quest’ultimi. Sono state inoltre eseguite prove di trazione per la caratterizzazione del materiale composito e dell'alluminio per ottenere parametri di input per le simulazioni numeriche. Le formulazioni analitiche e i modelli numerici risultano essere in buon accordo con i dati sperimentali in termini di curva balistica e morfologia del danno.
Experimental analysis and predictive modelling approaches for ballistic impact on multilayer shield
DI PRATOLA, VERONICA NORA
2018/2019
Abstract
Lightweight armours made of ceramic/composite or ceramic/metal materials have been highly investigated as ballistic protections through analytical and numerical models. Ceramic provides the capability of defeating armour piercing (AP) projectiles eroding projectile tip during the impact, while the composite or metal backing absorbs kinetic energy of the decelerated projectile and catches the ceramic and projectile fragments. Among the previous researchers, no attention was paid to evaluate the ballistic performance of a three-layered armour made of ceramic front face and a mixed composite and metal backing. This thesis presents two new analytical models for the evaluation of the ballistic behavior of three-layered targets. The new models combine the theoretical models of the multilayer ceramic/composite and ceramic/metal armour by introducing new parameters for the interaction between composite and metal plate. Numerical models on three-layer targets have been also performed with LS-DYNA ® software through fully Lagrangian finite-element analysis. The calibration of some parameters such as the erosion strain (FS) for the ceramic material, the Cockcroft-Latham parameter for aluminum alloy and the limit value in tension (SLIMT) for the composite led to achieve results in good agreement with experimental data. The validation of the predictive modelling approaches in terms of residual velocity and ballistic limit is conducted by means of experimental tests. Two specimens made of 8 mm alumina Al2O3, 7 layers Kevlar129 with Phenolic matrix and 2 mm aluminum alloy Al6082 - T6, with different arrangement of the backing, have been used for ballistic impact tests. Tensile tests for the material characterization of composite and aluminum were also performed to obtain input parameters for numerical simulations. The analytical formulations and numerical models result to be in good agreement with experimental data in terms of ballistic curve and damage morphology.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/151662