Executive Summary : | Nano-Alumina reinforced cellular-Al 6xxx cermet has been considered for current study to obtain light weight armor with good strength and minimal residual stresses. Al 7xxx and 5xxx alloys are commonly used in commercial armors, however these alloys suffer from problem of wearing out of unacceptable amount of debris under multiple ballistic impacts. It is therefore important to examine other commercially available aluminium alloys as substitution to current available ballistic grade aluminium armor materials. Considering this, Al 6xxx alloys can become an optimal solution for light weight armor system. Amongst commonly used reinforcements used for armor applications i.e. Al2O3, SiC and B4C. B4C after impact exhibit amorphism rendering the armor unusable while SiC is generally not compatible with the aluminium matrix, resulting in improper wettability and hence generation of in-built residual stresses. Considering, compatibility between matrix and reinforcement plays significant role in obtaining strong interfaces, for current study nano Al2O3 is chosen as reinforcement for Al 6xxx alloy. To further enhance the shatter resistance, Al 6xxx foam matrix is proposed to be used to improve the ballistic strength along with reduced weights. Such foam structures can be developed either by direct route as blowing gas (eg. Air) or indirect route as addition of foaming agent (eg. TiH2, CaCO3) to the melt during casting. To develop functionally graded structure, simple cost-effective vertical stir casting technique and diffusion bonding can be utilized. A typical stir casting route to achieve foam structure is shown in Fig 3. Graded structure can be achieved by controlling the settling of alumina particles (density 3.95 g/cc) in aluminium matrix (density 2.7 g/cc) under the effect of stirring force and gravity.Though various research works have been performed on development of armor systems that are capable to mitigate new threats. However, none of the study clearly establishes on the beneficial effect of using the combined design involving ‘Functionally Graded Nano Al2O3 Reinforced Al 6xxx Composite Foam' to obtain light weight armor structure with good ballistic strength and minimal residual stresses. |