Smart Hybrid ZnO Nanowire/carbon Fiber Reinforced Polymer Composites with In-situ Structural Health Monitoring Capability

Abstract

Structural fiber reinforced plastics (FRPs) composites are increasingly replacing metals due to their high specific stiffness and strength. However, FRPs are prone to delamination failure due to insufficient adhesion between the fiber and matrix or due to unexpected overloading. As delaminations reduce the structural stability and durability of FRPs leading to failure, structural health monitoring (SHM) is needed to detect delamination at early stages. This study suggests growing nanoscale ZnO piezoelectric nanowires (NWs) on the surface of carbon fabrics to act both as (1) sensor/transducer for SHM and (2) as an interfacial strengthening mechanism to mitigate delamination in the first place. The study employs a synergistic approach involving processing and characterization of hybrid polymer matrix composites based on ZnO NWs/carbon fibers and characterizing them mechanically and piezoelectrically. The in-situ SHM system utilizes electromechanical impedance based methods for early delamination detection and diagnosis. Utilizing a low temperature (85 °C) hydrothermal synthesis technique, ZnO nanowires were grown on the surface of woven carbon fiber (CF) and woven glass fiber (GF) fabrics. Hybrid Carbon FRPs were fabricated and tested via high velocity (~90 m/s) impact tests, and the impact energy dissipation and delamination failure mitigation capabilities of the FRPs were investigated. A 20% improvement in impact energy dissipation, and 16% reduction in delamination length of the FRPs were observed through whiskeriaztion of the carbon fiber fabrics with surface grown ZnO NWs. Hybrid CF-GF-CF composite laminates comprising different predesignated delamination depths were also fabricated to investigate the effect of damage severity on the electro-mechanical impedance of the FRPs. A correlation between the delamination severity and change in the FRPs’ impedance was established. The developed ZnO NWs based SHM provides a truly coupled structure-actuator system and benefits from large arrays of active regions within the composite which has many advantages for early detection of delamination in FRPs.