The effect of positional instability on the detection of barely visible impact damage in composites using a mobile thermographic inspection robot

Abstract

Abstract. As the use of composite materials continues to expand within the aerospace domain and elsewhere, the demand for rapid impact damage detection capabilities is also increasing. Line-scan thermography (LST) is a promising inspection modality where a light source focused to a line is swept over a structural component and sub-surface damage is highlighted as a thermal signature detectable via infrared imaging. This paper presents a rapid LST robotic inspection system combining ground-based robotics, advanced infrared imaging technology and dynamic image processing that is capable of achieving detection of barely visible impact damage in composite structures. The robotic system is evaluated experimentally on carbon fibre composite laminate specimens containing synthetic flat-bottom-hole defects, at scan speeds ranging from 25 mm/s to 100 mm/s. A study into the effect of positional instability on the capacity of the inspection system to detect damage is undertaken by introducing controlled perturbations in the robot path. Finite element modelling is also presented and verified against experimental results. Understanding the effect of positional instability on defect detection is important as work progresses towards an aerial drone-based implementation of this inspection capability.