Functionalized Aramid Fibers and Composites for Protective Applications: A Review

Technological growth in advanced ammunition and weapons has led to development of protective antiballistic composites, which are mostly based on aramid fibers, as they absorb high impact energy, arising from penetrators. Enhanced performance of aramid fibers (modulus similar to 112,400 MPa) is attributed to their compact molecular structure, hydrogen-bonding, high crystallinity, and high density (similar to 1.44 g/cm(3)). Methodologies such as layer-by layer, shear thickening, yarn pull-out, and surface functionalization via nanomaterials have been reported for modification of aramid fibers, which are widely used with thermosets like epoxy (due to process-friendliness). Recently, researchers are exploring thermoplastics with aramids, due to their higher toughness, chemical resistance, and thermal stability. Modification of aramid fibers is mostly performed using nanomaterials, e.g., carbon nanotubes, graphene, silk fibroins, SiO2, and ZnO, for enhancing their performance and minimizing fiber buckling under load. This Review presents advances in modification of aramid fibers using nanomaterials with emphasis on thermoplastics for protective applications, their stress transfer mechanisms, and life cycle analysis and concludes with their recycling/recovery methods.