Thermography as a tool for damage assessment (original) (raw)
Related papers
2012
Nowadays the use of technologically advanced materials such as composites is gaining an increasing interest due to their high strength to weight ratio and the possibilities to design optimum materials for specific applications that they offer. However, the utilization of these new advanced materials involves the requirements of application of also new quality control methods. A new generation of NDT techniques is being developed together with the composite materials. One of these new inspection techniques which has demonstrated good capabilities to measure the integrity of the composite materials is the Infrared Thermography (IRT). Although thermographic NDT techniques present many interesting advantages the main limitation appears in the detection of in-depth defects, due to the low penetration of the introduced heat inside the materials under test. IRT is applicable for surface and sub-surface defects detection. To overcome this limitation of the infrared technology, scientific re...
APPLICATION OF DIGITAL INFRARED THERMOGRAPHY FOR NONDESTRUCTIVE EVALUATION OF COMPOSITE BRIDGE COMPONENTS ARCHANA VASUDEVAN The objective of this research is to evaluate the applicability of digital infrared thermographic system to detect subsurface defects such as debonds and delaminations in Fiber Reinforced Polymer (FRP) bridge decks and other composite bridge components such as beams and columns wrapped with steel or FRP jacket. Infrared thermography is one of the nondestructive evaluation (NDE) techniques that are being used for testing field bridges and ensuring continued structural integrity of bridge components. The infrared technique allows rapid data collection and interpretation in the field. Also, recent advances in digital infrared imaging has opened the door for using more advanced image enhancement techniques, which can lead to better sensitivity and reliability in the detection of subsurface defects. This thesis investigates the use of digital infrared thermography on FRP bridge decks both under laboratory and field conditions. Air-filled and water-filled debonds were inserted between the wearing surface and the underlying FRP deck. Also, simulated subsurface delaminations (of various sizes and thickness) were created at the flange-to-flange junction between two FRP deck modules. The infrared technique was used to detect these embedded subsurface defects. Also, the use of various heating and cooling methods was explored. The effect of distance on the detectability of debonds and delaminations were considered. Surface temperature-time curves were established for different sizes of delaminations and debonds. As a part of this research two infrared field tests were conducted. One of the field trips was conducted to locate debonds in an FRP bridge deck. The other field trip involved inspecting and locating debonds in FRP wrapped timber railroad bridge components. Other types of bridge components considered in the laboratory studies included steel-concrete composite columns with embedded debonds and FRP wrapped wooden members for debonds or cracks. The results show that infrared thermography is a useful tool for defect detection in composite decks. Therefore, the technique can be used for several applications such as quality control during pultrusion of new decks (in factories), during field construction, and field inspection of in-service decks. The technique was also successful in detecting subsurface defects in various other composite components considered in this study.
Geometrical Limitations to Detection of Defects in Composites by Means of Infrared Thermography
Journal of Nondestructive Evaluation, 2004
The aim of the present experimental study is to gain information about limits in detection of defects in composites by infrared thermography. Specimens are manufactured of either carbon/epoxy, or glass/epoxy, and with inclusions of foreign materials to simulate defects of different size and positioned at different depths. Tests are carried out by using both pulse and lockin techniques. Results are presented in terms of difference of temperature (pulse), or difference of phase angle (lockin), between damaged zones and sound material. It seems that, apart from diameter and depth, the thickness is very crucial for defects visibility.
2007 Joint 32nd International Conference on Infrared and Millimeter Waves and the 15th International Conference on Terahertz Electronics, 2007
Multi-layered composites are frequently used in many military applications as constructional materials and light armours protecting personnel and armament against fragments and bullets. Material layers can be very different by their physical properties. Therefore, such materials represent a difficult inspection task for many traditional techniques of non-destructive testing (NDT). Typical defects of composite materials are delaminations, a lack of adhesives, condensations and crumpling. IR thermographic NDT is considered as a candidate technique to detect such defects. In order to determine the potential usefulness of the thermal methods, specialized software has been developed for computing 3D (threedimensional) dynamic temperature distributions in anisotropic six-layer solid bodies with subsurface defects. In this paper, both modeling and experimental results which illustrate advantages and limitations of IR thermography in inspecting composite materials will be presented.
Plastics, Rubber and Composites, 2011
The present study is concerned with the reliability and effectiveness of innovative non-destructive techniques for damage characterisation and evaluation of aerospace materials and structures. Infrared thermography (IrT) was used with the aim of assessing the integrity of bonded repair on aluminium substrates. For this purpose, artificial damage of various dimensions was introduced in composite laminates. These defects were successfully monitored with IrT using different imaging techniques. IrT was also employed for the online monitoring of the loaded structure. The real time evolution of progressive debonding owing to fatigue loading was monitored. No external thermal stimulation was necessary as the cyclic loading provided thermal excitation on the system. The experimental results provided evidence that the innovative technique was capable of qualitatively and quantitatively assessing the integrity of patched repairs. In other words, this technique can be efficiently employed for damage identification and quantification.
Measure of fracture toughness in composite structures using Infrared Thermography
HAL (Le Centre pour la Communication Scientifique Directe), 2014
Fracture toughness is one of the most important properties of any material for a lot of design applications involving damage and crack growth. Unfortunately its value can be difficult to evaluate with standard methods such as "compliance" method. In this work, two special cases have been studied and infrared thermography has been used to overcome the limitations of conventional methods. Damage of compressive fiber failure in unidirectional composite laminate has been chosen due to its difficulty to evaluate toughness. The infrared thermography has been used to follow compressive failure mode developing during an indentation test and a compression after impact test, and to evaluate the fracture toughness of compressive fiber failure.
IR Thermography Nondestructive Testing Methods of Composite Materials Used in Aerospace Applications
Proceedings of the 2015 Asia International Conference on Quantitative InfraRed Thermography, 2015
In case of composite materials we have to deal with the presence of both high mechanical resistance parameters and low specific gravity. Hence in recent years their use rapidly grows in structures for which these characteristics are of paramount importance. There are mainly aerospace structures. Typical defects of composite materials are: delaminating, lack of adhesion, cracks, concentrations and deformations. These defects can come into being both in manufacturing processes and during exploitation. With the development of technology for producing composite materials the requirements are growing for assessment of their quality. For this purpose nondestructive testing (NDT) is used. NDT procedures using IR thermography can be divided into passive and active. For the diagnosis of defects in composite materials of aerospace applications the active IR thermography methods are used in many cases. The paper presents examples of selected results of defects detection and description of used methods.
A review of thermographic techniques for damage investigation in composites.PDF
The aim of this work is a review of scientific results in the literature, related to the application of thermographic techniques to composite materials. Thermography is the analysis of the surface temperature of a body by infrared rays detection via a thermal-camera. The use of this technique is mainly based on the modification of the surface temperature of a material, when it is stimulated by means of a thermal or mechanical external source. The presence of defects, in fact, induces a localized variation in its temperature distribution and, then, the measured values of the surface temperature can be used to localize and evaluate the dimensions and the evolution of defects. In the past, many applications of thermography were proposed on homogeneous materials, but only recently this technique has also been extended to composites. In this work several applications of thermography to fibres reinforced plastics are presented. Thermographic measurements are performed on the surface of the specimens, while undergoing static and dynamic tensile loading. The joint analysis of thermal and mechanical data allows one to assess the damage evolution and to study the damage phenomenon from both mechanical and energetic viewpoints. In particular, one of the main issues is to obtain information about the fatigue behaviour of composite materials, by following an approach successfully applied to homogenous materials. This approach is based on the application of infrared thermography on specimens subjected to static or stepwise dynamic loadings and on the definition of a damage stress, D , that is correlated to the fatigue strength of the material. A wide series of experimental fatigue tests has been carried out to verify if the value of the damage stress, D , is correlated with the fatigue strength of the material. The agreement between the different values is good, showing the reliability of the presented thermographic techniques, to the study of composite damage and their fatigue behaviour.
A review of thermographic techniques for damage investigation in composites
Frattura ed Integrità Strutturale
The aim of this work is a review of scientific results in the literature, related to the application of thermographic techniques to composite materials. Thermography is the analysis of the surface temperature of a body by infrared rays detection via a thermal-camera. The use of this technique is mainly based on the modification of the surface temperature of a material, when it is stimulated by means of a thermal or mechanical external source. The presence of defects, in fact, induces a localized variation in its temperature distribution and, then, the measured values of the surface temperature can be used to localize and evaluate the dimensions and the evolution of defects. In the past, many applications of thermography were proposed on homogeneous materials, but only recently this technique has also been extended to composites. In this work several applications of thermography to fibres reinforced plastics are presented. Thermographic measurements are performed on the surface of the specimens, while undergoing static and dynamic tensile loading. The joint analysis of thermal and mechanical data allows one to assess the damage evolution and to study the damage phenomenon from both mechanical and energetic viewpoints. In particular, one of the main issues is to obtain information about the fatigue behaviour of composite materials, by following an approach successfully applied to homogenous materials. This approach is based on the application of infrared thermography on specimens subjected to static or stepwise dynamic loadings and on the definition of a damage stress, D , that is correlated to the fatigue strength of the material. A wide series of experimental fatigue tests has been carried out to verify if the value of the damage stress, D , is correlated with the fatigue strength of the material. The agreement between the different values is good, showing the reliability of the presented thermographic techniques, to the study of composite damage and their fatigue behaviour.
Proceedings of the 2012 International Conference on Quantitative InfraRed Thermography, 2012
Fiber reinforced polymers (FRP) composites are an efficient method in the strengthening of civil structures. FRP systems are usually applied by means of a wet lay-up method. National guidelines recognize that Infrared Thermography (IRT) is a possible non-destructive evaluation (NDE) technique for the detection of bonding defects, voids and damages and the characterization of the surface layers without a direct contact between the device and the observed area. Conversely, in the guidelines no clear indications are given about the inspection procedure.