FIRST BALLISTIC EVALUATIONS OF ALUMINIUM-BASED NANOCOMPOSITES CONSOLIDATED BY THE SPS PROCESS

摘要

Ballistic protections, more particularly body armour and lightweight armoured vehicles, require the development of advanced materials combining high mechanical strength, high ductility and low weight. The powder metallurgy way was used for the development of aluminium based composites strengthened both by nanostructuring and by the addition of nanodiamonds. Aluminium based specimens of 80 mm in diameter and 20 mm in thickness were consolidated by SPS process (Spark Plasma Sintering) and characterized in terms of structural and physical characteristics and of mechanical properties. After a parametric study and the optimization of the synthesis conditions, according to Archimedes’s method measurements, densities very close to the theoretical ones were reached. Quasistatic (QS) compression tests were carried out on the specimens as well as on aluminium alloys currently used in AFV’s (Armoured Fighting Vehicles). The comparison in terms of true stress values in QS conditions revealed that the best sintered specimens exhibit similar values to a 7020-T6 commercial aluminium alloy. Ballistic experiments with 7.62 AP steel core bullets were performed at ISL against a combination of nanostructured materials as front plate and AA7020-T6 as rear plate. The residual velocity of the projectile was measured by flash X-rays. A 10 mm thick AA7020-T6 backing plate was used in order to accentuate the differences between the residual velocities and thus to highlight the differences between the ballistic performances of the specimens. The very promising results reveal that the best specimen exhibits approximately 10% higher velocity reduction of the projectile than the best tested commercial aluminium alloy, to know the 7075 reference. In terms of absorbed energy, an improvement of 35 to 40 % was measured in comparison to commercial ballistic alloys. The powder activation, sintering and composition of the specimens are discussed based on the mechanical properties and ballistic performances.