Indian Journal of Science and Technology

Abstract

Background/Objective: To find an easy method to health monitor structures. Method: Self sensing or smart behavior has been observed in mortar or concrete with the addition of small amounts (0.2 to 0.5% by volume of cement) of short (5mm length) carbon fibres. It is seen that there is an increase in electrical resistance on loading upto crack propagation or fracture. On reaching the inelastic stage, the resistance change is not reversible. Findings: A method is developed which can be used in place of, often used strain gage technique or fibre optic technique for health monitoring of structures. There is an increase in resistance during fibre pull out in the elastic range. The change in elastic resistance was measured by a four probe method and was seen to be reversible for elastic deformation. Also, the crack propagation and fibre breakage of the specimen can be identified by irreversible resistance change. The stress vs strain and resistance vs strain graphs when plotted show similarity. Application: This phenomenon can be made use of to find the real time weight of vehicles in traffic and finding stress values of a loaded structure etc. 
Keywords: Carbon Fibre, Health, Monitoring, Resistance-Strain, Sensor, Stress-Strain