Modification of Pullout Behavior of Kevlar Fabric by Zinc Oxide Nanowire Reinforcement

The future development of body armor is to develop a lightweight, and wearable garment system without a loss of ballistic impact resistance. High performance fabrics, such as Kevlar, have been utilized for body armor due to their high energy absorption and lightweight characteristics. However, additional reinforcement is necessary for Kevlar fabric to meet the protection requirements for body armor against typical ballistic threats. Thick layers of fabric or embedded ceramic plates have been used to meet these requirements at the expense of increased weight of the armor and reduced mobility of the user. Thus, much research has been conducted on this topic to increase the ballistic impact resistance of Kevlar fabrics, mainly focused on the understanding and modeling of ballistic impact behavior. Due to the significant effect of damage mechanisms on ballistic impact response, these mechanisms should vastly be studied to better understand the ballistic impact response of Kevlar. When a projectile impacts a woven fabric, the imparted energy is dissipated through several damage mechanisms including tow pullout, local tow failure at the point of impact, and remote tow failure. Among those mechanisms, tow pullout is especially critical in the case of a penetrator with a blunt face impacting a fabric with non-penetrating velocities and is strongly influenced by friction between tows. In this work, we employed a novel method to increase the friction between Kevlar tows by synthesizing zinc oxide nanowires onto the fabric surface. As a result, vertically-aligned zinc oxide nanowires were grown on the fabric surface and tailored to achieve an optimum ballistic performance response reaching an enhancement of up to 390% in tow pullout peak load compared to untreated fabrics. Additionally, the effect of various surface functionalization processes and nanowire morphology is investigated so that an optimum process is developed for an efficient ballistic performance response.