Metal, concrete, and composite structures exposed to cyclic loading, corrosion, and abuse, are susceptible to fatigue cracking, strain, and ultimately, structural failure. As a result, monitoring this critical infrastructure is of vital importance before the damage reaches a critical stage and the structure fails.
Current structural monitoring of this damage has its challenges. Despite the fact that an estimated 3% of the US GNP gross national product is spent on replacing, repairing, inspecting, and/or monitoring fatigue damaged structures, conventional methods, such as structural inspections, can be periodic at best and may be conducted only over a period of several months to years. Existing technology, which can be expensive, is location-limited and can be only applicable during periodic inspections. As a result, damage may not be detected until it becomes severe. Even if the damage is detected, the structural damage may be difficult to monitor in a time-based manner- particularly if the area is in difficult-to-monitor areas, such as insulated pipes/tanks, or is comprised of different layers of material, such as composite structures.
MCET is developing a low-cost CNT-based sensing system that can be flexible for application to a wide range of fatigue sensitive details, durable, and reliable over the years of anticipated service life.Tests examining fatigue crack propagation in structural steel with a composite repair and integrated bondline sensing using MCET piezoresistant sensors increased the fatigue life by 380% to over 500%, depending on configuration. The sensing layer was able to monitor deformation and crack propagation in real-time and shows potential for use in periodic inspection-based monitoring of cracks using electrical property changes.
Full paper: "Integration of carbon nanotube sensing skins and carbon fiber composites for monitoring and structural repair of fatigue cracked metal structures" Elsevier (2018)