Ceramic Armors Research Articles

Numerical analysis for design of bioinspired ceramic modular armors for ballistic protections

The exigent requirements for personal protections in terms of energy absorption and ergonomics have led to increasing interest in bioinspired protections. This work focuses on the numerical analysis of ballistic behavior of different bioinspired geometries under impact loadings. Ceramic armors based on ganoid fish scales (the type exhibited by gars, bichirs and reedfishes), placoid fish scales (characterizing sharks and rays) and armadillo natural protection have been considered. Different impact conditions are studied, including perpendicular and oblique impacts to surface protection, different yaw angle, and multiple impacts. Main conclusion is related to the improved efficiency of modular armors against multiple shots exhibiting more localized damage and crack arrest properties. Moreover, its potential ergonomic is a promising characteristic justifying a deeper study.

Experimental study on the penetration effect of ceramics composite projectile on ceramic / A3 steel compound targets

Abstract In order to improve the penetration of projectiles into ceramic composite armors, the nose of 30 mm standard projectile was replaced by a toughened ceramic nose, and the performance of ceramic-nose projectiles penetrating into ceramic/A3 steel composite targets has been experimentally researched. According to impact dynamics theory,, the performances of 30 mm ceramic-nose projectile and 30 mm standard projectile penetrating into the ceramic/A3 steel composite targets were analyzed and compared using DOP method, especially focusing on the effects made by different nose structures and materials. The aperture and depth of perforation of projectile into the armor plates as well as the residual mass of bullet core under the same conditions were comparatively analyzed. A numerical simulation was built and computed by ANSYS/LS-DYNA. Based on the simulated results, the penetration performance was further analyzed in terms of the residual mass of bullet core. The results show that the ceramic nose has a great effect on the protection of bullet core.

Investigation on high-velocity impact performance of multi-layered alumina ceramic armors with polymeric interlayers

In this study, ballistic behavior of multi-layered ceramic armors under high velocity impact is studied numerically. The model consists of 2D-axisymmetric Lagrangian approach with Johnson–Holmquist constitutive model for alumina ceramic tiles, Mie–Gruneisen equation of state for polymeric interlayers, and Johnson–Cook constitutive relation for Armor Piercing (AP) projectile. The finite element results obtained from various armor layups show the potentiality of multi-layered ceramic armor in extending conoid fracture through the ceramic layers, thus leading to the increase in the armor performance. It is illustrated that besides ceramic armor layup, interlayers of ceramic tiles have a significant role in increasing the armor performance. Finally, the effect of different polymeric interlayers on ballistic performance of multi-layered ceramic armors against AP projectile is investigated. In order to measure the ballistic performance of the armors, various criteria are introduced. Depth of penetration of the projectile in the armor, residual velocity of the projectile, time duration in which the projectile is engaged inside the armor, projectile tip erosion during impact, and interaction volume ratio are some of these criteria. The study indicates that armor layup with thin front ceramic tiles backed by thicker tiles shows better conoid fracture extension and often better ballistic performance. Furthermore, among the polymeric interlayers used between the ceramic tiles, polystyrene causes the best and nylon causes the worst ballistic performance in the armor.

A study of the penetration behaviour of mild-steel-cored ammunition against boron carbide ceramic armours

In this study, the penetration behaviour of a Mild Steel Cored (MSC) round, 7.62 mm in diameter and 39 mm in length, commonly known as the AK47 round, was studied since it still forms an important part of the threat spectrum for personnel body armour systems. Likewise, boron carbide strike face materials were selected since this armour material is often the material of choice for ultralightweight body armour systems for protection against this particular threat.The presence of two, relatively soft, intermediate materials (the copper jacket and filler material of the bullet, and a fibre-reinforced polymer cladding layer on the ceramic) between the mild steel core and the boron carbide target was examined using reverse ballistics techniques, flash x-radiography and round recovery measurements. This was supported by selective numerical simulations using the computer code ANSYS-AUTODYN.It was found that stripping of the jacket, from the AK47 MSC rounds, makes a difference to its penetrating ability: the mild steel core is significantly reduced in length, and mass, when the jacket is not present. The magnitude of this effect is much greater than previously reported for high-strength steel-cored rounds and for tungsten carbide-cored rounds. The penetration event appears to be a twostage process: mushrooming of the mild steel core on, or near, the surface of the ceramic, followed by a linear erosion process as the core penetrates the ceramic itself. The second step has not been reported previously for MSC rounds.

Numerical Study on the Anti-Ballistic Properties of Metal Encapsulating Ceramic Composite Armors

The impact responses and ballistic resistance of the metal encapsulating ceramic composite armors with same area density and two hybrid cores are investigated. The hybrid cores include square metallic lattice with ceramic block insertions, and square metallic lattice with ceramic ball insertions and void-filling epoxy resin. Three-dimensional (3D) finite element (FE) simulations are carried out for each composite armors impacted by bullet with 12.7mm diameter. The focus is placed on the energy absorption capabilities and ballistic limit velocity of different composite armors. Results indicate that two kind of armors can improve the ballistic resistance properties and save mass of 22% and 25% compared to the homogeneous 4340 steel, respectively.

Hidden energy dissipation mechanism in nacre

Abstract

Effective damage mechanisms and performance evaluation of ceramic composite armors subjected to impact loading

Researches on the armor systems composed of composite materials with ceramic frontal face and polymer-based back-support are continuously developing further. This study, which mainly covers the impact behavior of ceramic composite armors, is a two-stage research. The first stage involves the investigation of component-level impact characteristics and failure mechanisms of the ceramic composite armors. At this stage, low-velocity impact behavior of ceramics and fiber-reinforced composites is investigated. Impact test results revealed that impact loading is of dynamic nature and strength of the composite materials under dynamic loading increases considerably as a result of strain rate sensitivity, which makes them the right choice to be used in conjunction with ceramics in armor systems. The second stage examines the ballistic impact behavior and ballistic performance of the armor systems. The extent and pattern of impact damage related to projectile velocity are determined for the armor components and the armor itself.

Ballistic Studies on TiB2-Ti Functionally Graded Armor Ceramics

The objective of this paper is to discuss the results of the ballistic testing of spark plasma sintered TiB2-Ti based functionally graded materials (FGMs) with an aim to assess their performance in defeating small-calibre armor piercing projectiles. We studied the efficacy of FGM design and compared its ballistic properties with those of TiB2-based composites as well as other competing ceramic armors. The ballistic properties are critically analyzed in terms of depth of penetration, ballistic efficiency, fractographs of fractured surfaces as well as quantification of the shattered ceramic fragments. It was found that all the investigated ceramic compositions exhibit ballistic efficiency (eta) of 5.1 -5.9. We also found that by increasing the thickness of FGM from 5 mm to 7.8 mm, the ballistic property of the composite degraded. Also, the strength of the ceramic compositions studied is sufficient to completely fracture the nose of the pointed projectile used. Analysis of the ceramic fragments (2 mu m-10 mm) showed that harder the ceramic, coarser were the fragments formed. On comparing the results with available armor systems, it has been concluded that TiB2 based composites can show better ballistic properties, except B4C. SEM analysis of the fragments obtained after testing with FGM showed formation of cleavage steps as well as presence of intergranular cracks, indicating that the FGM fractured by mixed mode of failure. It can be concluded that the FGM developed has lower ballistic properties compared to its monolith TiB2-20 wt.% Ti.

Simulation on Ceramic Composite Armors against Multi-Hit of APPs

The multi-hit of armor piercing projectiles (APPs) is one of the main treats to lightweight vehicles. Based on published ballistic experiments of Al2O3/Al2024 laminated composite armors against 7.62mm APP, the debonding of ceramic tiles was successfully simulated by setting reasonable material model and contact algorithm. A method named Geometric Intervals Method (GIM) was developed for simulation of multi-hit and its feasibility and rationality were investigated with the finite element code LS-SYNA. The numerical results shows that GIM has taken into account the effects of target damage caused by former APP impact on the target responds to later APP penetration. GIM can be used to simulate composite amours against multi-hit.

Experimental study on trepanning drilling of the ceramic composite armor using a sintering diamond tool

Laminated ceramic composite armors made of engineering ceramics, fiber-enforced composite, and lightweight alloy are expected to be used widely in armor protection area. However, secondary machining is still a problem for the distinct properties of composing materials, and up to now, few reports can be found out about machining technology. In this work, an experimental study on drilling a typical laminated ceramic composite armor by using a special sintering diamond thinwall trepanning tool has been carried out deeply. To improve the machining efficiency, process parameters including the spindle speed and the axial force have been optimized through drilling experiments. Moreover, the three phases of the whole drilling process of the typical ceramic composite armor is proposed, and the machining mechanism and chip forms in each phase have been analyzed. Also, diamond tool skidding phenomena whether at hole exit or during drilling middle engineering ceramics have been explored, and the skidding mechanisms are presented. In addition, the surface quality of a hole wall machined has been studied, and an advisable measure is given. Results achieved in this paper can provide a technical base for diamond trepanning tool drilling similar laminated ceramic composite armors.

Analysis of failure of add-on armour for vehicle protection against ballistic impact

The deployment of peacekeeping forces in conflict areas has shown that some armour systems are not sufficient to meet the latest threats. This applies particularly to lightweight vehicles whose armours give protection only against low calibre ammunitions. The development, production and fielding of add-on armours gives the answers to the demand for mission adjustable protection systems. Add-on armours represent a new protection philosophy, because they are produced as a separate kit, designed to achieve different protection levels. They have several advantages: Separate transport of armour and vehicle, they can be screwed to the main skull structure by crews and they are easily repairable or upgraded. Advanced add-on armours are produced by a clever combination of ceramic tiles backed by metal or composite plates. The utilization of advanced ceramics began in the 1960s when the US Army was demanding lightweight body armours for helicopter crews. Nowadays a wide spectrum of advanced ceramics is currently used for armour production, including alumina, silicon carbide, titanium diboride and boron carbide. Ceramics possess a high protection potential due a moderate density combined to a high compressive strength. But they are too brittle to be used without a ductile material backing. The design of ceramic add-on armours is a difficult task due to the high number of parameters involved: material selection, thicknesses of different materials, impact obliquity, etc. A design based exclusively on experimental tests is therefore expensive in money and time. This paper summarizes the utilization of analytical and numerical computation of ceramic/metal and ceramic/composite add-on armour failure process as valuable tools for armour design optimisation. Some examples are presented showing a good agreement between analytical, numerical and experimental results of residual mass and residual velocity of kinetic energy projectiles after perforation of the add-on armour.

Slow drag in polydisperse granular mixtures under high pressure

The behavior of polydisperse granular materials, composed of mixtures of particles of different sizes, is studied under conditions of high pressure and confinement. Two types of experiments are performed. In the first type, granular mixtures are compressed, with the resulting force-displacement curve used to calculate density and volume modulus. In the second set of experiments, the drag force is measured by pulling a cylinder, horizontally, through a compressed granular mixture. The density, volume modulus, and drag forces for the mixtures are quantified in terms of the mixture composition. The results show that the behavior of these mixtures depends strongly on the mass fractions of the different sized particles, with density, volume modulus, and drag force all reaching values significantly higher than observed in the monodisperse granular materials. Furthermore, the trends for density and drag force show strong correlation, suggesting that drag resistance of confined granular media could be directly related to packing effects. These results should prove useful in understanding the physics of drag in granular materials under high pressure, such as ballistic penetration of soils or ceramic armors.

Dynamic Compressive Response of Intact and Damaged AD995 Alumina

The dynamic compressive responses of AD995 alumina have been determined as a function of loading rates and damage levels. To determine the dynamic properties under loading conditions simulating those encountered in ceramic armors subjected to impact, a novel dynamic compressive experimental technique modified from a split Hopkinson pressure bar (SHPB) was employed to load the ceramic specimen by two consecutive stress pulses. The first pulse determines the dynamic response of the intact ceramic material and then crushes the specimen. Before the specimen disintegrates, the second pulse determines the dynamic compressive constitutive behavior of the ceramic rubble that is still interlocked. The results show that the compressive strengths of damaged ceramics are insensitive to strain rates once the damage level exceeds a critical value.

Slow drag in granular materials under high pressure.

The resistance offered by a cylindrical rod to creeping cross flow of granular materials under pressure is investigated. The experimental system consists of a confined bed of granular particles, which are compacted under high pressure to consolidate the granular medium. A cylindrical rod is pulled at a constant and slow rate through the granular medium, and the measured pulling resistance is characterized as a drag force. The influence of various parameters such as the velocity of the cylindrical rod, the rod diameter and length, the granular particle size, and the compaction pressure on the required drag force is investigated experimentally. Nondimensional analysis is performed to simplify the relationships between these variables. The results show that the drag force is independent of the drag velocity, is linearly proportional to compaction pressure and rod diameter, and increases with rod length and particle size. Additional compaction experiments show that the effective density of the granular bed increases linearly with pressure, and similar behavior is noted for all particle sizes. These results should prove useful in the development of constitutive equations that can describe the motion of solid objects through compacted granular media under high pressure, such as during ballistic penetration of soils or ceramic armors.

Investigation on Fracture Behavior of Armor Ceramics Against HEAT Penetration

In this study, the jet tip of high explosive anti tank (HEAT) within the ceramic target was trapped to investigate the interaction of the jet with the ceramic during HEAT penetration. Some trials, the introduction of a stand-off to regulate the jet amount without degrading the jet velocity and the adoption of the bonded specimen method, were devised for the HEAT firing test. These facilitated the examination of the internal damage induced in ceramic targets of 85% alumina (AD 85) and hot-pressed SiC (HS) in its impacted state. The fracture mechanisms of ceramic targets against HEAT penetration are discussed. The fracture behaviors of ceramic targets were of different shapes and the extent of the cracks depended upon the fracture and deformation behavior occurring ahead of the jet tip and around the penetration site. For AD 85 targets, the dynamic compaction of comminuted fine particles and powders occurred due to high pressure at the leading edge of the penetrating jet and around the penetrated regions. In the case of HS targets, however, high dense cracks occurred at the region ahead of the jet tip. Through fractographic observations of the damage zones on the contact surfaces, the fracture behavior of ceramic armors against jet penetration can be explained by the comminution zone model.

Numerical simulation of normal and oblique ballistic impact on ceramic composite armours

This paper presents three-dimensional finite element models that investigate the performance of ceramic–composite armours when subjected to normal and oblique impacts by 7.62 AP rounds. The finite element results are compared with experimental data from different sources both for normal and oblique impact, respectively. Simulation of the penetration processes as well as the evaluation of energy and stresses distributions within the impact zones highlight the difference between normal and oblique ballistic impact phenomena. The findings show that the distributions of global kinetic, internal and total energy versus time are similar for normal and oblique impact. However, the interlaminar stresses at the ceramic–composite interface and the forces at the projectile–ceramic interface for oblique impact are found to be smaller than those for normal impact. Finally, it is observed that the projectile erosion in oblique impact is slightly greater than that in normal impact.

The adaptive and erosive numerical modelling of confined boron carbide subjected to large-scale dynamic loadings with element conversion to undeformable meshless particles

In recent years, developments in the field of lightweight armour have been of primary importance to the defence industry. This necessity has led to many organisations adopting composite armours comprising both traditional heavy armours and new lighter weight ceramic armours. The numerical modelling of metal based armour systems has been well documented over the years; and more recently advanced numerical methods have been utilised for the computational modelling of ceramic armour systems. It is the goal of this paper to demonstrate how a commercial finite and discrete element code, such as ELFEN, can be used in the further understanding of the response of combined ceramic/metal armour systems when subjected to large-scale dynamic loads through the combined techniques of adaptive remeshing, material erosion and particulate methods. It is well established that penetration processes can be modelled using standard material erosion techniques. However for many brittle materials, including ceramics, the material regions close to the impact interface undergo comminution, which can effectively be numerically modelled as a continuum that will typically exhibit flow like behaviour. Furthermore, use of the commonly employed erosive techniques allows unavoidable material relaxation through element removal leaving voids at the impact interface, which for ceramic type materials introduces an invalid increased rate of damage accrual and hence an incorrect material response. One of the primary objectives of this paper is to present a new computational method which automatically transforms deformed finite elements into undeformable meshless particles. In addition, to overcome severe element conditioning associated with large deformation problems; it will be shown that this technique can be successfully coupled with adaptive remeshing techniques, which are themselves coupled to standard material erosion processes. An example presenting the potential benefits of this form of domain update method, in contrast to the traditionally used material erosion techniques, will be demonstrated for the computational modelling of brittle materials used in multiple component armour systems, which are frequently encountered within today's defence industry.

The numerical modelling of ceramics subject to impact using adaptive discrete element techniques

In recent years, developments in the field of lightweight armour have been of primary importance to the defence industry. This necessity has led to many organisations adopting composite armours comprising both the traditional heavy armours and new lighter weight ceramic armours. The numerical modelling of metal based armour systems has been well documented over the years using purely continuum based methods; and also the modelling of brittle systems using discrete element methods, therefore it is the objective of this paper to demonstrate how a coupled finite and discrete element approach, can be used in the further understanding of the quantitative response of ceramic systems when subjected to dynamic loadings using a combination of adaptive continuum techniques and discrete element methods. For the class of problems encountered within the defence industry, numerical modelling has suffered from one principal weakness; for many applications the associated deformed finite element mesh can no longer provide an accurate description of the deformed material, whether this is due to large ductile deformation, or for the case of brittle materials, degradation into multiple bodies. Subsequently, two very different approaches have been developed to combat such deficiencies, namely the use of adaptive remeshing for the ductile type materials and a discrete fracture insertion scheme for the modelling of material degradation. Therefore, one of the primary objectives of this paper is to present examples demonstrating the potential benefits of explicitly coupling adaptive remeshing methods to the technique of discrete fracture insertion in order to provide an adaptive discontinuous solution strategy, which is computationally robust and efficient.

The effect of obliquity on the ballistic performance of two component composite armours

Summary This paper examines the performance of composite armours when subjected to oblique impact. Experimental results are presented from a programme of trials on ceramic-aluminium targets using 7.62 mm ball ammunition. The results show that an inclined ceramic composite armour plate will perform better, on a thickness basis, than one arranged perpendicular to the line of impact. However, the degree of improvement thus obtained is much less than for steel armours. Moreover, it is shown that minimum weight protection to a vulnerable area, using ceramic composite armours, is achieved when the armour is perpendicular to the threat. The degree of thickness reduction which is obtained by angling ceramic composite armours is much less than for steel armours. A theoretical model of oblique impact is presented and shown to correlate well with the experimental results.

Deformation energy of Kevlar backing plates for ceramic armours

Deformation energy of Kevlar backing plates for ceramic armours