Development of technical bases for using infrared thermography for nondestructive evaluation of fiber reinforced polymer composites bonded to concrete

摘要

Fiber-reinforced polymer (FRP) composites, in the form of pultruded laminates or built-up woven fabrics, are being used widely to strengthen existing concrete and masonry structures. The success of these materials in performing their intended functions depends, to a large extent, on how well they are bonded to themselves and to the substrate. There is a need for an efficient and reliable method to detect and characterize defects at the substrate interface and within multi-ply systems. Infrared thermography is well suited for this purpose because it is inherently sensitive to the presence of near-surface defects and can interrogate large areas efficiently. Before infrared thermography can be developed into a standard methodology, however, an understanding is needed of the effects of testing parameters and different types of defects. This dissertation focuses on establishing the potential for quantitative infrared thermography, that is, not only detecting but also characterizing subsurface flaws. Numerical and experimental methods are used to investigate the effectiveness of infrared thermography to estimate the width of subsurface flaws in fiber-reinforced polymer laminates bonded to concrete. First, a dimensional analysis of a simplified case of one-dimensional heat diffusion in an infinite half space is performed to establish the parameters that affect the thermal response of the test object.