Novel distributed strain sensing in polymeric materials

Abstract

Monitoring the state of strain throughout an entire structure is essential to determine itsstate of stress, detect potential residual stresses after fabrication, and also to help toestablish its integrity. Several sensing technologies are presently available to determine thestrain in the surface or inside a structure. Large sensor dimensions, complex signalconditioning equipment, and difficulty in achieving a widely distributed system havehowever hindered their development into robust structural health monitoring techniques.Recently, carbon nanotube forests were spun into a microscale thread that is electricallyconductive, tough, and easily tailorable. The thread was integrated into polymericmaterials and used for the first time as a piezoresistive sensor to monitor strain andalso to detect damage in the material. It is revealed that the created self-sensingpolymeric materials are sensitive to normal strains above 0.07% and that the sensorthread exhibits a perfectly linear delta resistance–strain response above 0.3%. Thelongitudinal gauge factors were determined to be in the 2–5 range. This low costand simple built-in sensor thread may provide a new integrated and distributedsensor technology that enables robust real-time health monitoring of structures.