Design of Carbon Nanotube Sheet Embedded Fiber Composites with In Situ Structural Health Monitoring Capability

Damage accumulation in fiber composites is complex and incipient damage is difficult to detect using conventional non-destructive evaluation techniques. Different damage modes ranging from micro-level to macro-level (fiber breakage, micro and transverse matrix cracks development, fiber-matrix de-bonding, delamination, etc.), will affect the structural performance and durability of the materials. There is an emerging need for smart composite materials with self-damage sensing capabilities to increase the reliability of composite materials. Recently, advances in macroscopic forms of carbon nanotube materials provide the potential for structural health monitoring using carbon nanotube sheets integrated in the interlaminar areas of advanced fiber composites. This research explores the fabrication of fiber composites with laminated carbon nanotube sheets embedded for strain sensing and damage detection based on the spatial electrical property changes of the carbon nanotube sheets. The mechanical-electrical response behavior is recorded under multiple loading conditions, including quasi-static and impact loading, and the data are analyzed to determine the sensing ability. The manufacturing process of integrating the carbon nanotube sheets into the system strongly affects the sensitivity and repeatability of the integrated multifunctional sensors. The ultimate goal of this research is to develop reliable structural health monitoring methods capable of obtaining information on the damage state in real-time.