Functionalized Aramid Fibers and Composites for Protective Applications: A Review

Abstract

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 ∼ 112,400 MPa) is attributed to their compact molecular structure, hydrogen-bonding, high crystallinity, and high density (∼1.44 g/cm3). 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.

Enhanced mechanical and tribological properties of Kevlar/PTFE‐phenolic composites by improving interfacial properties by aramid nanofibers

“…The dispersibility of fillers and interfacial interaction between fibers and polymer matrix are determined the mechanical properties of fibers or fabric strengthened polymer matrix composites. [ 28 ] Figure 4A and B shows the average bonding strength and stress‐displacement curves for the pristine and ANF‐modified Kevlar/PTFE‐phenolic composites. The bonding strengths of ANF‐modified composites are higher than those of pristine composites.…”

“…These results are mainly attributed to the high surface‐free energy and abundant reactive anchoring site such as carboxylic acids and amine function groups, which can promote chemical cross‐linking and curing the epoxy matrix. [ 28–29 ]…”

The Mechanical Properties of Kevlar Fabric/Epoxy Composites Containing Aluminosilicates Modified with Quaternary Ammonium and Phosphonium Salts

“…The fibers are usually glass, carbon, or aramid, which do not break by brittle cracking. Kevlar fiber reinforced composites (KFCs) have been widely used as impact-resistant structures, such as in anti-ballistic applications, due to their high degree of toughness, associated with the failure mechanism, damage tolerance, and good impact performance [ 1 , 2 , 3 , 4 ]. Despite the excellent properties of KFCs, there are some disadvantages, such as low stiffness and compression strength, limiting their application in the aviation industry, shipbuilding, or sport goods.…”

Atomistic simulations of functionalization of aramid fiber‐epoxy nanocomposite

“…2 Aramid fiber (AF) has excellent mechanical properties, high temperature resistance and anti-aging properties; thus, it has been receiving great attention for its applicability in polymer composite reinforcement. [3][4][5] However, the fiber has high degree of crystallinity and orientation, causing its surface to be smooth and chemically inert. For this reason, its bond strength with the polymer interface is low, in turn lowering the mechanical performance of the composites.…”