IFAC-PapersOnLine 49-28 (2016) 291–296 ScienceDirect ScienceDirect Available online at www.sciencedirect.com 2405-8963 © 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Peer review under responsibility of International Federation of Automatic Control. 10.1016/j.ifacol.2016.11.050 © 2016, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Keywords: composites, thermography, aircraft inspection, NDT, data processing 1. INTRODUCTION Aircraft components suffer tremendous amounts of tension and stress. The integrity of such a complex piece of machinery can be easily compromised by minor flaws that can lead to catastrophic events. Composites (carbon-fiber & glass-fiber) are a big part of an aircraft’s shuttle, however the aviation community is filled with conflicting or incorrect information about their safety and capability. The behaviour of the composite structures is very different under normal loads compared to equivalent metal structures. It has been proven through trials, that compared to metals, composite repair patches present less fatigue and corrosion. Undetected subsurface damage can go undetected for long periods and it can result in sudden catastrophic failures. Therefore, there is extreme importance in a truly innovative inspection process capable of identifying the condition of these materials. A large amount of work has been carried out to develop methods and systems for detecting manufacturing defects, fatigue cracking, structural discontinuities, accidental damage, build damage and environmental degradation in composites. However, despite the existence of traditional NDT methods in aerospace applications such as those used for the inspection of metallic materials, in several instances they are unsuited for the inspection of composite structures. NDT engineers are still restricted to manually driven technology that is unrepeatable and subjective; being prohibited from employing new techniques that are quantifiable, robust, repeatable and reproducible until research provides solid evidence of solutions to these problems. This clearly emphasizes the need for a wider range of faster more accurate NDT techniques to meet the current and future inspection requirements that underwrite structural integrity of composites and composite structures. 1.1 IR inspection of aircraft composites Transient thermal Thermography and Near Infrared Imaging (Clemente Ibarra-Castanedo, 2012) are prompt and reliable techniques applied for the assessment of composites and composite components that find use in aircraft transport applications. An external source of energy is required in Transient IR Thermography NDT in order to induce a temperature difference between defective and non-defective areas in the specimen under examination. Energy sources can be divided in three categories: (i) Optical excitation, where the energy is delivered to the surface by means of optical devices and the light is transformed to heat. (ii) Halogen lamps (for periodic heating) utilizing thermal waves that propagate by conduction through the specimen. The waves reach a discontinuity that act as a resistance and are reflected back to the surface. (iii) Finally, mechanical excitation that heats up the defects internally with mechanical oscillations. There are two classical active thermographic methods: lock- in thermography and pulsed thermography which are applied externally. These techniques and their applications have both different experimental and theoretical aspects. Thermal maps i.e. thermograms are generated by IR thermography, operating in the mid-wave (MWIR) (3-5 μm) and long-wave (LWIR) (7.5-14μm) portions of the infrared spectrum, and they are the result of thermal emissions from the specimen surface. IR thermography is gaining popularity in many areas Abstract: The wide use of composite materials in a number of industrial sectors has necessitated the development of new nondestructive inspection techniques for both manufacturing quality assurance and in-service damage testing. This paper discusses the development of a new holistic inspection system for aircraft composite materials that is composed of three thermographic cameras (operating at different wavelengths such as Near-infrared, Mid-Wave and Long-Wave) placed on the head of a robotic arm. Different setups were investigated in order to achieve optimal settings for a variety of influencing parameters including camera distance from the surface under investigation, excitation source type and power. Experiments were also conducted to define the effectiveness of each thermographic camera towards a variety of defect types. Advanced image processing algorithms were further developed and deployed to enhance the inspection capabilities of the three cameras and improve the interpretation of the collected thermal images. Future work on validating fusion and machine learning tools, their integration as well as on-site inspections has been planned. Non-destructive inspection of aircraft composite materials using triple IR imaging S. Moustakidis*. A. Anagnostis**, P. Karlsson*, K. Hrissagis** *City University of London, London, United Kingdom (Tel: (+30)672863096 ; e-mail: serafeim.moustakidis.1@city.ac.uk) . **IRETETH Institute for Research and Technology Thessaly, CERTH Centre for Research & Technology Hellas, Thessaloniki, Greece (Tel: (+30)6947072707 ; e-mail: anagn@mail.ireteth.certh.gr)