Tailoring Metal Particle Deposition on Non-conductive Woven Fabrics for Multifunctional Applications Using an Electroplating Process

As engineering requirements become more multifarious and demanding, structural materials have a greater need to be multifunctional, in general. This is especially true for flexible composites used in aerospace and defense applications. In this study, the potential to tailor the deposition of metallic particles such as those of copper into non-conductive woven fabrics like Kevlar using an electroplating process is investigated to enhance their multifunctional utility. Customizing a standard electroplating process by replacing the cathode with a primer-coated Kevlar swatch, the influence of process parameters such as electroplating current and time, radial separation of electrodes, and priming and orientation of the Kevlar swatches, among others, are explored experimentally. An aqueous solution of copper-coated silver particles is used to coat the non-conductive swatch to the desired degree and pattern to act as a primer that initiates the electroplating process. The anode, which is a 0.03 mm-thick copper sheet and the cathode, which is an 80×120 mm2 swatch of plain-woven style 745 Kevlar 29 fabric are configured as concentric cylindrical rings in a bath of 1M copper (II) sulfate solution, with the anode being the outside ring. The electroplating current and time can be optimized to ensure the desired percentage by weight of particle addition to the fabric. It is found that by calibrating degree and pattern of the conductive primer on the fabric, the deposition can be tailored to result in conductive pathways on the fabric. Likewise, anisotropy or bias in the deposition levels can be engineered by combinations of priming and orientation variations. For instance, when the priming is done on the inner (non-anode facing) side, the particle depositions preferentially occur in the interstitial spaces of yarn crossover points rather than on the yarn bundle tops. This is attributed to the path of least resistance to the primed surface offered to the copper ions by the interstitial spaces of the fabric. The formation of large nodules in the interstitial spaces enhances inter-yarn friction leading to the engagement of secondary yarns under ballistic impact, which is known to improve the protective performance of Kevlar. Scanning Electron Microscopy [SEM] imaging is conducted to better understand the morphology of the deposition and interaction between the Kevlar fibers and the particles. Further, the deposition of conductive metallic particles into Kevlar has the benefit of being able to embed smart functionalities into wearables such as armor or protective gear. In addition, the uniform conductivity lent to the fabrics through this controllable process could act as a surrogate or marker for further multifunctional treatment with other colloidal or dry nanoparticles using manual or automated processes with lesser control over uniformity. By calibrating the change in conductivity, the accuracy and uniformity of this secondary, nonconductive nanoparticle treatment could be gauged. This allows for the bulk evaluation of such nanoparticle-treated flexible composites without resorting to more resource-intensive techniques such as SEM imaging. Proof-of-concept studies are presented for this approach.