Materials

Research

12 pages, 3549 KiB

Open AccessArticle

Drop Weight Testing of Samples Made of Different Building Materials Designed for the Protection of Classified Information

by Jakub Durica, Andrej Velas, Martin Boros, Radoslav Sovjak, Petr Konrad and Premysl Kheml

Materials 2023, 16(3), 1219; https://doi.org/10.3390/ma16031219 - 31 Jan 2023

Viewed by 1328

Abstract

Classified information is information of vital importance to the State, which must be protected against disclosure, misuse, damage, unauthorized reproduction, destruction, loss or theft in the interest of the State. At present, there are four levels of classification. For each classification level, precise [...] Read more.

Classified information is information of vital importance to the State, which must be protected against disclosure, misuse, damage, unauthorized reproduction, destruction, loss or theft in the interest of the State. At present, there are four levels of classification. For each classification level, precise requirements are laid down for the material of the walls, partitions and ceilings of the rooms in which classified information is stored. Several types of materials are defined for each classification level. The objective of this study was to test and determine whether the different types of materials proposed for the Confidential level meet the same level of resistance. A drop weight test via pendulum was used to determine the resistance. A 50 kg weight was used to break through a 60 × 100 cm sample. The impact of the weight was on the exact center of the sample. The result of the tests was that to break through samples of different materials, large differences in the drop height of the weight were required. The most resistant was the specimen made of reinforced concrete, which required 3 impacts from a height of 80 cm to break through. On the contrary, the least resistant were the specimens made of masonry of autoclaved aerated concrete, where after 2 falls from a height of 5 cm, the sample broke into 2 parts. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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14 pages, 3354 KiB

Open AccessArticle

Influence of the Accelerated Aging Process on the Fragment-Resistant Properties of Para-Aramid Body Armor

by Katarzyna Kośla, Marcin Łandwijt, Michał Miklas and Marzena Fejdyś

Materials 2022, 15(18), 6492; https://doi.org/10.3390/ma15186492 - 19 Sep 2022

Cited by 2 | Viewed by 1453

Abstract

Para-aramid materials such as Twaron^® and Kevlar^® are commonly used for ballistic-resistant body armor, which are designed to protect human life and health. For this reason, the materials from which body armor are made should be thoroughly investigated in the area [...] Read more.

Para-aramid materials such as Twaron^® and Kevlar^® are commonly used for ballistic-resistant body armor, which are designed to protect human life and health. For this reason, the materials from which body armor are made should be thoroughly investigated in the area of long-term reliability, particularly with regard to exposure to UV light, humidity and temperature, as these are known causes of degradation in commonly used ballistic materials. This research presents the durability of soft and hard ballistic inserts designed using para-aramid (Twaron^®) materials. Para-aramid ballistic inserts not subjected to accelerated aging processes and also ones subjected to laboratory aging for 63, 129 and 194 days, which corresponded to 2, 4 and 6 years of aging in real conditions, were tested. The selected para-aramid inserts were verified in terms of ballistic and physico-mechanical properties as well as changes in chemical structure of the ballistic materials. Ballistic tests were carried out with the use of a 1.1 g FSP.22 fragment according to STANAG 2920. Changes in the microstructure of the para-aramid materials were evaluated using infrared spectroscopy and scanning electron microscopy. The obtained results indicate that despite the changes which took place at the molecular level in the Twaron^® materials, accelerated aging processes do not affect the fragmentation resistance properties of ballistic inserts made of para-aramid materials. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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18 pages, 7020 KiB

Open AccessArticle

Prediction of Abrasive Waterjet Machining Parameters of Military-Grade Armor Steel by Semi-Empirical and Regression Models

by Soundarapandian Rammohan, Sundaresan Thirumalai Kumaran, Marimuthu Uthayakumar, Kinga Korniejenko, Marek Nykiel and Arumugam Velayutham

Materials 2022, 15(12), 4368; https://doi.org/10.3390/ma15124368 - 20 Jun 2022

Cited by 4 | Viewed by 1781

Abstract

Rolled homogeneous armor steel (RHA) with a high tensile strength, toughness, and hardness is often used in military combat vehicles. RHA is a high-strength low alloy steel suitable for all battlefield usage in military vehicles. The present work examines the prediction output responses [...] Read more.

Rolled homogeneous armor steel (RHA) with a high tensile strength, toughness, and hardness is often used in military combat vehicles. RHA is a high-strength low alloy steel suitable for all battlefield usage in military vehicles. The present work examines the prediction output responses in the material removal rate (MRR), surface roughness (Ra), and kerf angle (Ka) for the AWJM of armor steel using regression and semi-empirical models. The AWJM trials were performed using an L27 factorial design with each process variable set to three levels, namely, the standoff distance (SOD), jet traversing speed (JT), and jet water pressure (P). A regression model was constructed using the response surface method (RSM) and data from the trials. Through dimensional analysis and with Buckingham’s π-theorem, a semi-empirical model was built using both the experimental data and material property data. Predictions made by the models were proportionate with the results of the experiments under the same conditions. Microscopic investigations on MRR and Ra were performed using a scanning electron microscope (SEM). The optimal values of the output responses of the machined armor steel plate were obtained with higher MRR = 298.92 mm³/min, lower Ka = 0.651°, and lower Ra = 2.23 µm. The present work established that semi-empirical models accurately predict the output responses in the AWJM of armor steel. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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16 pages, 1736 KiB

Open AccessArticle

Fragment-Resistant Property Optimization within Ballistic Inserts Obtained on the Basis of Para-Aramid Materials

by Katarzyna Kośla, Paweł Kubiak, Marcin Łandwijt, Wioleta Urbaniak and Agnieszka Kucharska-Jastrząbek

Materials 2022, 15(6), 2314; https://doi.org/10.3390/ma15062314 - 21 Mar 2022

Cited by 4 | Viewed by 1900

Abstract

A high protection level without an excessive weight is a basic assumption in the design of modern armors and protection systems. Optimizing armors is a task of development of the utmost importance, and is the subject of the work contained within this article. [...] Read more.

A high protection level without an excessive weight is a basic assumption in the design of modern armors and protection systems. Optimizing armors is a task of development of the utmost importance, and is the subject of the work contained within this article. Optimization of ballistic inserts was carried out using multicriterial analysis (MCA), which enables the selection of the optimal composition, taking into account properties such as ballistic resistance, physicomechanical, and/or functional properties. For this purpose, various types of composite systems were produced and tested in terms of their fragment-resistant properties according to STANAG 2920 and the composite areal density of different ballistic inserts: Soft inserts made of Twaron^® para-aramid sheets, hard ballistic inserts made of multilayer hot-pressed preimpregnated sheets, and hybrid hard ballistic inserts prepared on the basis of multilayer hot-pressed preimpregnated sheets and ceramics. The application of MCA and performance of experimental fragment resistance tests for a wide spectrum of para-aramid inserts are part of the novelty of this work. The obtained test results showed that depending on the composition of the composite system, we could obtain a wide range of fragmentation resistance in the range of 300 to >1800 m/s, which depended on the areal density and type of composite system used. The results also confirmed that MCA is a good computational tool to select the optimal design of para-aramid ballistic inserts. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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13 pages, 5183 KiB

Open AccessArticle

Determining Ricocheting Projectiles’ Temperature Using Numerical and Experimental Approaches

by Przemysław Badurowicz and Dawid Pacek

Materials 2022, 15(3), 928; https://doi.org/10.3390/ma15030928 - 25 Jan 2022

Cited by 4 | Viewed by 2047

Abstract

This paper describes the process of creating a numerical FEM (finite element method) model of the 5.56 × 45 mm SS109 projectile. The model was used to calculate the temperatures occurring in the projectile materials during the impact on the steel plate at [...] Read more.

This paper describes the process of creating a numerical FEM (finite element method) model of the 5.56 × 45 mm SS109 projectile. The model was used to calculate the temperatures occurring in the projectile materials during the impact on the steel plate at an angle of 45°. The purpose of the investigation is to estimate the ability of a ricocheting projectile to cause ignition. For the same projectile, experimental tests were also carried out under the conditions adopted for the numerical investigation in order to validate the FEM model. During the experiment, temperature was measured with a thermal camera; the phenomenon was also recorded with a colour high-speed camera. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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22 pages, 6936 KiB

Open AccessArticle

High-Velocity Impacts of Pyrophoric Alloy Fragments on Thin Armour Steel Plates

by Evaristo Santamaria Ferraro, Marina Seidl, Tom De Vuyst and Norbert Faderl

Materials 2021, 14(16), 4649; https://doi.org/10.3390/ma14164649 - 18 Aug 2021

Cited by 3 | Viewed by 2251

Abstract

The terminal ballistics effects of Intermetallic Reactive Materials (IRM) fragments have been the object of intense research in recent years. IRM fragments flying at velocities up to 2000 m/s represent a realistic threat in modern warfare scenarios as these materials are substituting conventional [...] Read more.

The terminal ballistics effects of Intermetallic Reactive Materials (IRM) fragments have been the object of intense research in recent years. IRM fragments flying at velocities up to 2000 m/s represent a realistic threat in modern warfare scenarios as these materials are substituting conventional solutions in defense applications. The IRM add Impact Induced Energy Release (IIER) to the mechanical interaction with a target. Therefore, the necessity of investigations on IIER to quantify potential threats to existing protection systems. In this study, Mixed Rare Earths (MRE) fragments were used due to the mechanical and pyrophoric affinity with IRM, the commercial availability and cost-effectiveness. High-Velocity Impacts (HVI) of MRE were performed at velocities ranging from 800 to 1600 m/s and recorded using a high-speed camera. 70 MREs cylindrical fragments and 24 steel fragments were shot on armour steel plates with thicknesses ranging from 2 mm to 3 mm. The influence of the impact pitch angle (α) on HVI outcomes was assessed, defining a threshold value at α of 20°. The influence of the failure modes of MRE and steel fragments on the critical impact velocities (CIV) and critical kinetic energy (

E_{kin crit}

) was evaluated. An energy-based model was developed and fitted with sufficient accuracy the Normalised

E_{Kin crit}

(

{\tilde{E}}_{k i n}^{c r i t}

) determined from the experiments. IIER was observed in all the experiments involving MRE. From the analyses, it was observed that the IIER spreads behind the targets with velocities comparable to the residual velocities of plugs and shattered fragment. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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21 pages, 2332 KiB

Open AccessArticle

Comparative Study on High Strain Rate Fracture Modelling Using the Application of Explosively Driven Cylinder Rings

by Marvin Becker, Tom De Vuyst, Marina Seidl and Miriam Schulte

Materials 2021, 14(15), 4235; https://doi.org/10.3390/ma14154235 - 29 Jul 2021

Viewed by 1564

Abstract

The effect of different constitutive modelling choices is crucial under a high strain rate as encountered in ballistic applications. Natural fragmentation of explosively driven cylinder rings is chosen as a simplified example to describe the ability of numerical simulations to describe fractures. The [...] Read more.

The effect of different constitutive modelling choices is crucial under a high strain rate as encountered in ballistic applications. Natural fragmentation of explosively driven cylinder rings is chosen as a simplified example to describe the ability of numerical simulations to describe fractures. The main research interests are the importance of (i) material imperfections, (ii) the accuracy of fracture models vs. damage models, (iii) the plasticity algorithm (stress update), (iv) the introduction of a triaxiality cutoff criterion to the damage models, and (v) different constitutive models (plasticity and damage). Due to the complexity of the propagation and coalescense of multiple cracks in classical methods, smoothed-particle hydrodynamics (SPH) is used as a tailor-made method to discretise the model. An elasto-plasticity model, a damage model and an equation of state describe the material behaviour. The required material parameters are determined based on stress–strain curves from quasi-static and dynamic tests. The Johnson–Cook model, with and without a modification of the strain rate term, and the Rusinek–Klepaczko model are used to describe plasticity. These plasticity models are combined either with the Johnson–Cook, the Lemaitre, or the Dolinski–Rittel damage model and the Mie–Grüneisen equation of state. The numerical results show that (i) a random distribution of initial damage increases irregularity of cracks, and gives more realistic fragment shapes, (ii) a coupling of plasticity model and fracture criterion has only a small effect on the fracture behaviour, (iii) using an iterative plasticity solver has a positive effect on the fracture behaviour, although this effect is marginal, (iv) adding a triaxiality cutoff criterion to the damage models improves the predicted fragment masses in the numerical simulations significantly, and (v) good accordance between experiments and numerical simulations are found for the Dolinski–Rittel and Lemaitre damage model with both plasticity models. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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16 pages, 5360 KiB

Open AccessArticle

Sacrificial Cladding with Brittle Materials for Blast Protection

by Ludovic Blanc, Thérèse Schunck and Dominique Eckenfels

Materials 2021, 14(14), 3980; https://doi.org/10.3390/ma14143980 - 16 Jul 2021

Cited by 10 | Viewed by 1987

Abstract

In the following work, sacrificial claddings filled with different brittle materials were investigated, from concrete foam to granular media. They were subjected to blast loading using an explosive driven shock tube, while a sensor measures the load transmission and a high speed camera [...] Read more.

In the following work, sacrificial claddings filled with different brittle materials were investigated, from concrete foam to granular media. They were subjected to blast loading using an explosive driven shock tube, while a sensor measures the load transmission and a high speed camera records the compression of the core. From a macroscopic point of view, concrete foam and granular media can act efficiently as a crushable core but differs greatly in terms of energy dissipation mechanisms. To compare them, granular media was at first treated as a cellular material, and different key parameters (plateau stress, densification strain) were computed using the energy absorption efficiency methodology. The presented tests results, coupled with observation in literature, allow a better understanding on the crushing process of a granular media. In particular, granular media tend to work as a core even for low intensity load, contrary to more classical crushable core. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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17 pages, 5673 KiB

Open AccessArticle

Dynamic Equilibrium of CFRP-RC Square Elements under Unequal Lateral Impact

by Khalil AL-Bukhaiti, Liu Yanhui, Zhao Shichun, Hussien Abas and Dong Aoran

Materials 2021, 14(13), 3591; https://doi.org/10.3390/ma14133591 - 27 Jun 2021

Cited by 11 | Viewed by 1842

Abstract

Building structure regularly needs reinforcement due to damage, specification requirements, and functional changes; carbon fiber reinforced polymer (CFRP) is widely used in structural reinforcement due to its high strength, lightweight, good corrosion resistance and easy construction. The regular square section reinforced concrete frame [...] Read more.

Building structure regularly needs reinforcement due to damage, specification requirements, and functional changes; carbon fiber reinforced polymer (CFRP) is widely used in structural reinforcement due to its high strength, lightweight, good corrosion resistance and easy construction. The regular square section reinforced concrete frame elements strengthened by CFRP material are taken as the research object. The dynamic response of CFRP to reinforced concrete elements under unequal lateral impact was discussed. This technical paper demonstrates that the test elements are subject to the bending failure mode, and the impact point and the near impact point support are severely damaged areas; the transversely wrapped elements are more abruptly broken, and the longitudinal wrapping elements and the number of wrapping layers can effectively reduce the level of damage. Analysis of the impact, deflection, and strain time history curves obtained in the test show that the wrapping mode and the number of layers have less influence on the impact force peak; the longitudinally wrapped elements and the plateau segment take longer. Dynamic equilibrium principle equation was proposed based on the experimental results. The horizontal partition plateau segment fluctuates greatly; the number of vertical wrap layers increases the plateau value. The larger the number of layers, the smaller the deflection caused by the impact. The longitudinal wrapping can effectively transmit the force. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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17 pages, 5480 KiB

Open AccessArticle

Experimental and Numerical Study on a Non-Explosive Reactive Armour with the Rubber Interlayer Applied against Kinetic-Energy Penetrators—The ‘Bulging Effect’ Analysis

by Teresa Fras

Materials 2021, 14(12), 3334; https://doi.org/10.3390/ma14123334 - 16 Jun 2021

Cited by 5 | Viewed by 5976

Abstract

The study concerns a protection system applied against kinetic-energy penetrators (KEPs) composed of steel plates sandwiching a rubber layer. Laminated steel-elastomer armours represent non-explosive reactive (NERA) armours that take advantage of a so-called ‘bulging effect’ to mitigate KEP projectiles. Upon an impact, the [...] Read more.

The study concerns a protection system applied against kinetic-energy penetrators (KEPs) composed of steel plates sandwiching a rubber layer. Laminated steel-elastomer armours represent non-explosive reactive (NERA) armours that take advantage of a so-called ‘bulging effect’ to mitigate KEP projectiles. Upon an impact, the side steel plates deform together with the deforming rubber interlayer. Their sudden deformation (bulging) in opposite directions disturbs long and slender KEP projectiles, causing their fragmentation. The presented discussion is based on the experimental investigation, confirming that the long-rod projectiles tend to fracture into several pieces due to the armour perforation. A numerical simulation accompanies the ballistic test providing an insight into the threat/target interactions. The presented experimental–numerical study explains the principles of the analysed protection mechanism and proves the efficiency of the materials composition making up the laminated non-reactive protection system. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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28 pages, 14817 KiB

Open AccessArticle

Experimental and Numerical Study on the PG-7VM Warhead Performance against High-Hardness Armor Steel

by Paweł Żochowski, Radosław Warchoł, Maciej Miszczak, Marcin Nita, Zygmunt Pankowski and Marcin Bajkowski

Materials 2021, 14(11), 3020; https://doi.org/10.3390/ma14113020 - 02 Jun 2021

Cited by 18 | Viewed by 8832

Abstract

Analyses presented in the article were carried out in order to characterize the main parameters of the shaped charge jet formed due to detonation of the PG-7VM warhead. As opposed to the previously published studies in which rolled homogeneous armored steel was mainly [...] Read more.

Analyses presented in the article were carried out in order to characterize the main parameters of the shaped charge jet formed due to detonation of the PG-7VM warhead. As opposed to the previously published studies in which rolled homogeneous armored steel was mainly used as a target, in the current work the warhead penetration capability was determined against more contemporary high-hardness (500 HB) ARMSTAL 30PM steel armor with precisely determined mechanical properties. The research included experimental depth of penetration tests and their numerical reproduction in the LS-Dyna software. Special attention was paid to factors that could perturbate the shaped charge jet formation process and under- or overestimate its penetration capability. For this reason, warheads were X-ray inspected for structural discrepancies (voids or air inclusions in explosive, misalignment between the body, explosive, and liner, or lack of contact between the explosive and the liner) and properties of materials (explosive, targets, and most important warhead components) were analyzed before the experiments. The numerical model of the warhead was defined more accurately than in previously published studies, since it was based on the real grenade dimensions and its technical documentation. Thanks to this, the depth of penetration of the target made of ARMSTAL 30PM armored steel plates by the shaped charge jet formed from the PG-7VM warhead obtained by numerical simulation was consistent with the experimental results and equaled 278 mm and 280 mm, respectively. The difference between the experimental and numerical value was smaller than 1%, which confirms that the developed methodology of modeling allows users to properly reproduce the PG-7VM shaped charge jet formation and target penetration processes. A verified numerical model of the shaped charge jet penetration into a steel target was used to determine depth of penetration in function of stand-off distance for the PG-7VM warhead. A maximum depth of penetration of about 317 mm was obtained for the stand-off distance of 360 mm, which may indicate the potential direction of modernization of warheads. Full article

(This article belongs to the Special Issue Materials Dedicated for Armours and Protection Systems)

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