Infrared thermography for inspection of aramid and ultra-high-molecular-weight polyethylene armor systems

Non-Destructive Evaluation (NDE) trials were performed on aramid and ultra-high molecular-weight polyethylene (UHMWPE) based armor systems. Pulsed thermography, continuous heating, and lock-in thermography were investigated for various types of damage. It is shown that the infrared thermography results vary significantly based on the material and thickness of the armor system, and only certain types of damage can be confidently identified. While the pulsed thermography performed in reflection mode was the fastest and provided the strongest indication signal for some types of damage, deeper damage on thicker armor system needed to be performed in transmission mode. Due to inherent material properties variations in these armor systems, the infrared images were affected by non-uniformity. In addition, due to low thermal conductivity, the inspections were sporadically affected by non-uniform heating. Approaches are presented to address the non-uniform heating issue affecting the inspection of those low thermal conductivity materials.