Thermal image for monitoring crack forming process

Abstract

Thermal image is used to visualize the crack forming and progressing process in mortar prisms added with carbon fibers of five different percentages of 0.0 %, 0.5 %, 1.0 %, 1.5 % and 2.0% in volume, with the time variations of the surface temperature of the prisms while applying forces through a universal testing machine. The surface temperatures are smoothly increasing as the force increases but they reveal sudden temperature increases at the time of crack forming in the prisms. It turns that the sudden temperature increase in the prisms is appeared at the aggregated carbon fibers along the crack paths. The time of increasing matches closely to the crack on-set time determined by a panchromatic camera. Since the fibers along the crack path are more stressed for the given force because they resist more to the force than the mortar itself, their temperatures increase much more than the neighboring mortar. Hence the temperature variation in the aggregated fibers along the crack path informs before the actual crack appearance.