This paper presents the computational-based ballistic limit of laminated metal panels comprised of high strength steel and aluminium alloy Al7075-T6 plate at different thickness combinations to necessitate the weight reduction of existing armour steel plate. The numerical models of monolithic configuration, double-layered configuration and triple-layered configuration were developed using a commercial explicit finite element code and were impacted by 7.62 mm armour piercing projectile at velocity range of 900 to 950 m/s. The ballistic performance of each configuration plate in terms of ballistic limit velocity, penetration process and permanent deformation was quantified and considered. It was found that the monolithic panel of high-strength steel has the best ballistic performance among all panels, yet it has not caused any weight reduction in existing armour plate. As the weight reduction was increased from 20-30%, the double-layered configuration panels became less resistance to ballistic impact where only at 20% and 23.2% of weight reduction panel could stop the 950m/s projectile. The triple-layered configuration panels with similar areal density performed much better where all panels subjected to 20-30% weight reductions successfully stopped the 950 m/s projectile. Thus, triple-layered configurations are interesting option in designing a protective structure without sacrificing the performance in achieving weight reduction. Keywords Ballistic impact; ballistic limit; double-layered plate; numerical simulation; triple-layered plate N.A. Rahman et al. / Ballistic Limit of High-Strength Steel and Al7075-T6 Multi-Layered Plates Under 7.62-mm Armour Piercing…

This paper present the study about the mechanical properties of two high strength low alloy steels for replacing the current rolled homogeneous armour (RHA) for ballistic application. High strength low alloy steel has been widely adapted as a ballistic plate in light armoured vehicle. However, the current used RHA plate is very heavy thus restricted the manoeuvrability of the armoured vehicle. The aim of this study is to find materials suitable to be used for production of composite protection panel which is lighter yet has similar mechanical properties to RHA. The tensile strength and hardness of AISI 4340 and AR500 steels were evaluated and compared to that of RHA and the results were analysed based on its chemical compositions and microstructural observation. Values of these properties are primarily reflected by its microstructures and chemical compositions. Therefore, microscopic observation of microstructural arrangement and phases are essential in understanding the hardness and stress-strain behaviour of these metals. Results indicate similar tensile properties were observed in RHA and AR500 but different properties obtained for AISI 4340. Tensile strength of RHA and AR500 were 1750 MPa and 1740 MPa respectively followed by AISI 4340 at 1020 MPa. AISI 4340 steel exhibited the highest elongation at 20.6% compared to RHA and AR500 at 13.3 and 12.5%, respectively. Higher degree of carbon content in fine martensitic structure of RHA and AR500 led to high hardness. Imperfections in RHA and AR500 were also removed by hot rolling process as indicated by white banding that cause higher in tensile strength. Retained austenite and coarse microstructure of AISI 4340 steel contributed to higher ductility compared to AR500 and RHA. Therefore the tensile properties of RHA and AR500 were found similar due to its microstructure behaviour. This similarity allows AR500 to be utilised as alternatives to RHA in armour plate application.

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This paper intends to prepare a nanofluid sample by suspending Multi-walled Carbon Nanotubes (MWCNTs) at 0.005g/L concentration and analyze the behavior of electrical and dielectric properties based on the International Electrotechnical Commision test method. In order to validate the effectiveness of MWCNT nanofluid, alternating current breakdown voltage (BDV), negative polarity lightning impulse (LI), dielectric permittivity, dissipation factor (DF), DC resistivity and Raman structural measurement are executed accordingly. In the following, an analysis of the statistical distribution using the two-parameter Weibull distribution law of BDV and LI are evaluated at four experimental conditions to predict the probability of breakdown occurring at different percentages. Based on the observation, the MWCNT filler has a substantial effect in improving the BDV and LI characteristics of disposed mineral oil. The permittivity, DF and resistivity performance of MWCNT nanofluid from 25 °C to 90 °C also produces comparable and reliable performance as a fresh transformer oil. As for Raman structure, the revolution of transformer oil by doping MWCNT does not disrupt the original chemical structure of mineral oil. Hence, this study proves the improvement of the electrical and the behavior of dielectric properties and chemical structure of nanofluid, providing a huge contribution towards the development of insulating materials for transformer application.

This paper presents the effect of laminated aluminium-steel panel with different configurations in a high-speed impact test. Layering aluminium plate with high strength steel has become an interest in reducing the overall density of armour vehicle body while improving the ballistic resistance. Different layering configurations differ in laminated panel performance. Two layering configurations of double-layered panel achieving 25% of existing panel weight reduction were tested using experiment and computational method to investigate their behaviours when impacted with 7.62-mm full metal jacket at velocity range of 800–850 m/s. The ballistic performance of each configuration plate in terms of ballistic limit velocity, penetration process and permanent deformation was quantified and considered. Laminated panel with aluminium as the front layer reduced the ballistic performance of existing panel to 50% and the other panel maintained its performance. Thus, the laminated panel with aluminium as the back layer can be used in designing a protective structure for armoured vehicle while maintaining the performance of the existing vehicle in achieving weight reduction.

This paper investigates the computational-based deformation and energy absorption capability of laminated metal panels composed of high-strength steel and aluminium alloy under low-velocity impact. Layering aluminium alloy plates with high-strength steel has become of interest for reducing the overall density of armoured vehicle bodies while improving the ballistic resistance. In order to enhance the attractiveness of laminated plate construction, it is essential to study the strength of the two different metals in a laminated panel under low-velocity impact before performing a ballistic impact. Two types of laminated panels were constructed: two-layer and three-layer configurations. Both were oriented transverse to the loading axis and solved using quasi-static analysis. The deformation behaviour of these panels was studied and the energy absorption capacities were quantified. The results showed that the energy absorption capacities of the laminated panels were on average 220% higher in the three-layer configuration panels compared to in the two-layer configuration panels. The deformation lengths in the three-layer configuration panels were on average 22% smaller than those of the two-layer configuration panels with 25% to 30% weight reduction. The best three-layer configuration panel will be used later for investigating a suitable combination panel for armoured vehicles subjected to ballistic impact.

The joining of aluminium alloys to steels has been extensively studied, especially in the automotive sector. However, aluminium alloys are known to be difficult to join with steels when methods involving fusion welding are used because of the hot cracking problem. Hence, a high-strength joint between these dissimilar metals would be of benefit especially in reducing the weight of products. In this work, the torch-brazing method was applied to join AR500 steel with AA7075 aluminium alloy using Al–Si–Zn base filler metal at various flame times. The effects of the brazing work on the intermetallic phase formation and the mechanical strength of the joints were investigated. In this work, the maximum shear load obtained was 6460 N and the presence of the intermetallic phases had reduced the shear strength of the brazed joints. However, the torch-brazing process using Al–Si–Zn filler metal had successfully facilitated the joining of these dissimilar metals.

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