Carbon Tow Filaments and their Composites as Strain Sensors

The use of innovative fibers, that include carbon fibers, may support many important aspects in the building construction, making them stronger and more efficient. Carbon based textile materials, such as materials obtained by weaving and braiding techniques in composites with epoxy matrices, have been used in architecture and building design to reinforce building structures. The utilization of filaments and resin matrices is important due to the high strength of such composites, giving them the needed performance to reinforce concrete structures. However, the textile material used to reinforce structures can perform other functions, such as integrating sensors or monitoring sensors of some variables that are important in case of increased load, instability or deformation that for instance occurs with earthquakes. This paper analyses some carbon filament properties, textile structures and their composites with epoxy, with the goal to understand these materials ability to sense very low deformations. To understand how the carbon textile materials can sense and register such occurrences, the study focusses on the variation analysis of the carbon filaments electrical resistivity embedded in epoxy during tensile tests, performed at the dynamometer, and over concrete specimens. Both volume electrical resistivity and contact electrical resistivity of the composite materials were measured. The obtained results demonstrate the possibility of using carbon filaments to design textile materials able to sense very small strains in concrete structures.