Non-destructive evaluation (NDE) techniques are essential to detect damage in structures, including airplanes, and require further improvement. Extant NDE techniques are often time-consuming, and their spatial resolution and in situ capabilities are limited. In this paper, a new NDE technique is demonstrated using the Joule heating effect of carbon nanotube (CNT) networks embedded within structural composites (also known as nanoengineered composites). Via local resistive heating, damage in the composite causes increased electrical and thermal resistance that is visualized with standard thermographic imaging. Multiple improved characteristics have been experimentally confirmed, including real-time measurement, high resolution (∼0.1 mm), and simple and low-power (15 °C rise at 1 W) operation. Furthermore, the ability to detect barely visible (and internal) damage, and an additional de-icing functionality, are presented. This materials-based sensing technique offers a novel and practical approach for in situ structural health monitoring to prevent structural failures.