An experimental investigation of the effect of carbon nanotubes addition and shot peening process on the ballistic limit of fiber-metal laminates

Abstract

The present research has experimentally investigated the effect of adding multi-walled carbon nanotubes (MWCNTs) and shot peening operations on the ballistic behavior of fiber-metal laminates (FMLs). The unreinforced and reinforced FMLs with 0.2 wt.%, 0.4 wt.%, and 0.6 wt.%. of MWCNTs were manufactured by hand lay-up method and subjected to shot peening operations. Finally, the specimens were exposed to the ballistic impact test using a cylindrical projectile with a conical head. The best result was obtained for 0.4 wt.% of MWCNTs, in which the ballistic limit and absorbed energy increased by 6.80% and 13.75% for non-shotted and by 8.50% and 17.45% for shotted samples, respectively. This demonstrates the positive effect of shot peening in increasing the ballistic limit through a combination of work hardening and compressive residual stresses in the aluminum layers. However, mechanical performance decreased in samples containing 0.6 wt.% of MWCNTs due to nanoparticle agglomeration. The fracture surfaces of the samples were also analyzed by scanning electron microscopy, and the results indicated an improvement in the adhesion properties at the interface between the fibers and matrix in the reinforced samples, achieved through mechanisms such as crack bridging and MWCNTs pull-out.