Scalable, roll-to-roll manufacturing of multiscale nanoparticle/fiber composites using electrophoretic deposition: Novel multifunctional in situ sensing applications

Multiscale composites, where traditional fiber reinforcements are combined with nanoscale reinforcements, have emerged as multifunctional materials and have found potential for in situ strain and damage sensing, and energy harvesting/storage applications. Critical to the advancement of future applications is the development of manufacturing techniques that are industrially scalable. Electrophoretic deposition (EPD) can uniformly coat functionalized nanoparticles, such as carbon nanotubes (CNT), on conductive and non-conductive fiber substrates, producing multiscale composites with controlled microstructures and functional properties. In this research, a pilot-scale roll-to-roll EPD system is developed to continuously manufacture CNT-integrated fabrics for in situ sensing applications. Based on fundamental knowledge of CNT deposition mechanisms, key experiments are conducted to determine electrode configurations to optimize deposition yield in the roll-to-roll process. Functionalized CNTs are then deposited on 4-6 m long continuous rolls of randomly oriented non-woven glass fiber veil with different areal weights, and the CNTs form a continuous, conductive fiber-level coating. The thin and open fabric microstructure allows embedded sensors that are minimally invasive to the composite structure and allow ultraviolet (UV) light transmittance for use with UV-curable resins. The electrically conductive CNT network created on the fabric allows for the integration of sensing functionality. Short beam specimens with the CNT sensors embedded at the midplane showed no deterioration in strength. Multiple functionalities, including strain sensing and flow/UV cure monitoring during vacuum infusion are demonstrated. Sensors tested under flexural loading demonstrated sensitivity in tension and compression, and during resin infusion, the sensors could track resin flow and cure progression.