Abstract
The current necessity of the scientific and industrial community, for reduction of aircraft maintenance cost and duration, prioritizes the need for development of innovative nondestructive techniques enabling fast and reliable defect detection on aircraft fuselage and wing skin parts. Herein, a new low-cost thermographic strategy, termed Pulsed Phase-Informed Lock-in Thermography, operating on the synergy of two independent, active infrared thermography techniques, is reported for the fast and quantitative assessment of superficial and subsurface damage in aircraft-grade composite materials. The two-step approach relies on the fast, initial qualitative assessment, by Pulsed Phase Thermography, of defect location and the identification of the optimal material-intrinsic frequency, over which lock-in thermography is subsequently applied for the quantification of the damage’s dilatational characteristics. A state-of-the-art ultra-compact infrared thermography module envisioned to form part of a fully-automated autonomous nondestructive testing inspection solution for aircraft was conceived, developed, and tested on aircraft-grade composite specimens with impact damages induced at variable energy levels and on a full-scale aircraft fuselage skin composite panel. The latter task was performed in semi-automated mode with the infrared thermography module mounted on the prototype autonomous vortex robot platform. The timescale requirement for a full assessment of damage(s) within the sensor’s field of view is of the order of 60 s which, in combination with the high precision of the methodology, unfolds unprecedented potential towards the reduction in duration and costs of tactical aircraft maintenance, optimization of efficiency and minimization of accidents.
Highlights
In aircraft maintenance, inspection and quantification of damage by nondestructive testing (NDT)techniques, is currently the most reliable route towards the identification of superficial and—undetectable by visual inspection—internal defects in the airframe structure, and for assessing the extent of repair work required for extending the operational lifetime of the structures [1,2,3].Federal Administration Aviation (FAA) and European Aviation Safety Agency (EASA) regulations require aerospace industries to inspect, by reliable and efficient NDT techniques, all aircraft components for possible defects and flaws, at regular intervals before and during their service life
Thermograms can be recorded in sequence, and the results exported into maximum thermal in formats
The new PPI-lock-in thermography (LT) technique is based on the synergy of two complementary Infrared thermography (IRT) techniques for rapid assessment of damage at all subsurface depths
Summary
Inspection and quantification of damage by nondestructive testing (NDT). The total timescale requirement for a full assessment by PPI-LT of damage within the instant field of view (IFOV) of the IR module, was in the order of 60 s [48] This exceptionally low timescale, in combination with the material-extrinsic principles of the proposed approach—which enables applicability to other material classes—unravels unprecedented potential for substantial time and cost reductions in aircraft maintenance, especially C- and D-checks, but most importantly provides accurate, efficient and reliable damage inspection data for proper repair leading to increased aircraft performance, prevention of accidents and decrease of human life loss
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