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International audience; This research paper presents the application of the microwave infrared thermography (MIRT) technique for the purpose of detecting and characterizing defects in the carbon-fiber-reinforced polymer (CFRP) composite reinforcement of concrete specimens. Initially, a numerical model was constructed, which consisted of a broadband pyramidal horn antenna and the specimen. The present study investigated the application of a 360 W power system that operated at a frequency of 2.4 GHz, specifically focusing on two different operational modes: continuous and modulated. The specimen being examined consisted of a solid concrete slab that was coated with an adhesive layer, which was then overlaid with a layer of CFRP. Within the adhesive layer, at the interface between the concrete and CFRP, there was a defect in the form of an air gap. The study examined three distinct scenarios: a sample without any defects, a sample with a defect positioned at the center, and a sample with a defect positioned outside the center. The subsequent stage of the investigation incorporated experimental verification of the numerical modeling results. The experiment involved the utilization of two concrete specimens reinforced using CFRP, one without any defects and the other with a defect. Numerical modeling was used in this study to analyze the phenomenon of microwave heating in complex structures. The objective was to evaluate the selected antenna geometry and determine the optimal experimental configuration. Subsequently, these findings were experimentally validated. The observations conducted during the heating phase were particularly noteworthy, as they differed from previous studies that only performed observation of the sample after the heating phase. The results show that MIRT has the potential to be utilized as a method for identifying defects in concrete structures that are reinforced with CFRP.

L’urgence climatique nous pousse à revoir nos modèles sociétaux, notamment en matière de développement et de consommation. Dans le secteur de la construction, qui est l’un des plus impactant, une solution pour lutter contre le réchauffement global pourrait être d’utiliser une mixité de matériaux naturels, bio-sourcés ou géo-sourcés produits localement pour bâtir des habitats confortables, sains et durables. Cette étude est consacrée à deux nobles représentants de la catégorie, que sont la pierre naturelle calcaire et la fibre de bois. Les résultats expérimentaux issus de l’instrumentation d’échantillons de parois seront confrontés à des simulations numériques afin d’analyser les transferts couplés de chaleur et d’humidité et la pertinence des modèles pour ce type de matériaux. Une seconde partie présentera l’analyse environnementale de plusieurs maçonneries en pierres naturelles dans le but de déterminer les principaux flux contributeurs de l’impact., Academic Journal of Civil Engineering, Vol 40 No 1 (2022): Special Issue - RUGC 2022

International audience; The climate emergency makes us review our societal models, particularly in development and consumption. In the construction sector, which is one of the most impacting, a solution to fight against global warming could be to use a mix of natural, bio-sourced, or geo-sourced materials produced locally to build comfortable, healthy, and sustainable buildings. This study is devoted to two noble representatives of the category: natural limestone and wood fiber. Experimental results obtained from the instrumentation of wall samples will be compared with numerical simulations to analyze the coupled heat and moisture transfers and the relevance of the models for this type of material. The second part will present the environmental analysis of several natural stone masonries to determine the main contributing flows of the impact.; L'urgence climatique nous pousse à revoir nos modèles sociétaux, notamment en matière de développement et de consommation. Dans le secteur de la construction, qui est l'un des plus impactant, une solution pour lutter contre le réchauffement global pourrait être d'utiliser une mixité de matériaux naturels, bio-sourcés ou géo-sourcés produits localement pour bâtir des habitats confortables, sains et durables. Cette étude est consacrée à deux nobles représentants de la catégorie, que sont la pierre naturelle calcaire et la fibre de bois. Les résultats expérimentaux issus de l'instrumentation d'échantillons de parois seront confrontés à des simulations numériques afin d'analyser les transferts couplés de chaleur et d'humidité et la pertinence des modèles pour ce type de matériaux. Une seconde partie présentera l'analyse environnementale de plusieurs maçonneries en pierres naturelles dans le but de déterminer les principaux flux contributeurs de l'impact.

International audience

International audience; Natural stone is a traditional building material that has been used for millennia. However, even if its mechanical properties are well known, the data relating to environmental impacts and thermo-hydric transfers deserve further study. Indeed, in the current context of the fight against global warming, French thermal regulations for buildings tend to evolve towards more environmentally friendly constructions. This work aims to deepen our knowledge of the hygrothermal characteristics of a panel of twelve limestone rocks from local quarries, in parallel with the environmental analysis of the masonry associated with them. A statistical study makes it possible to study the correlations between their physical properties and to classify them by families. Because of a moderate environmental impact, the use of these rocks improves thermal inertia and can help regulate indoor humidity in buildings.; La pierre naturelle est un matériau de construction traditionnel utilisé depuis des millénaires. Cependant, même si ses propriétés mécaniques sont bien connues, les données relatives aux impacts environnementaux et aux transferts thermo-hydriques méritent d’être approfondies. En effet, dans le contexte actuel de lutte contre le réchauffement climatique, la réglementation thermique française des bâtiments tend à évoluer vers des constructions plus respectueuses de l’environnement. Ce travail vise à approfondir la connaissance des caractéristiques hygrothermiques d’un panel de douze roches calcaires issues de carrières locales, en parallèle à l’analyse environnementale des maçonneries leur étant associé. Une étude statistique permet d’étudier les corrélations entre leurs propriétés physiques et de les classer par familles. Au regard d’un impact environnemental modéré, l’emploi de ces roches permet d’améliorer l’inertie thermique et peut contribuer à réguler l’humidité intérieure des bâtiments.

International audience

Carbon Fiber Reinforced Polymers (CFRPs) have been increasingly employed for structural strengthening, and are attached to structures using bonding adhesives. The aim of this work is to characterize defects in the bond between CFRP and concrete (after they are located by pulse infrared thermography), and assign the defects a “numerical value” (ranging from 0 for a complete air–gap to 1 for a fully glued bond). Quantitative characterization is performed by measuring the thermal impedance, and then identifying the thermophysical parameters of the system through fitting the measured impedance to a theoretical model. An inversion procedure is carried out to estimate the unknown parameters, without prior knowledge of sample properties. In particular, it is possible to estimate more accurately both the amount of glue within a defect and the thermal contact resistance.

National audience

CCBY; International audience; This paper presents two infrared thermography methods with CO2 Laser excitation and microwave excitation applied to defect detection in CFRP. The tests were conducted with two specimens, one with defect, and another one without defect. On two concrete plates 40 cm× 40 cm× 4.5 cmwere reinforced by CFRP; the defects were made by the absence of adhesive on an area10 cm× 10 cm. The specimens were heated by microwave, generated by a commercial magnetron of 2.45 GHz and guided by a pyramidal horn antenna, with a power of 360 W within 150 s. Another series of the tests was conducted with CO2 Laser, wavelength 10.6 μm, by heating the samples with a power of 300 W within 40 s. An infrared camera sensitive to medium waves in range of 3 - 5 μm, with a detector of 320 × 256 matrix detector in InSb (Indium Antimonide), was used to record the thermograms. As a result, the CO2 Laser excitation is better for the delamination detection in CFRP. This study opens interesting perspectives for inspecting other types of defects in materials sciences; the microwave excitation is suitable for the deep defects in the materials whereas the CO2 Laser excitation is better for the defects near the surface of the materials.

This paper presents a NDT by infrared thermography with excitation CO2 Laser, wavelength of 10.6 μm. This excitation is the controllable heating beam, confirmed by a preliminary test on a wooden plate 1.2 m x 0.9 m x 1 cm. As the first practice, this method is applied to detecting the defect in CFRP heated by the Laser 300 W during 40 s. Two samples 40 cm x 40 cm x 4.5 cm are prepared, one with defect, another one without defect. The laser beam passes through the lens of a deviation device, and heats the samples placed at a determinate position and area. As a result, the absence of adhesive can be detected. This method displays prominently its application as NDT with the composite materials. This work gives a good perspective to characterize the laser beam, which is very useful for the next detection campaigns., {"references":["Ch. Maierhofer, A. Brink, M. Röllig, H. Wiggenhauser, \"Transient thermography for structural investigation of concrete and composites in the near surface region,\" Infrared Physics & Technology, vol. 43, pp. 271-278, 2002.","Jeff R. Brown, H. R. Hamilton, \"Quantitative infrared thermography inspection for FRP applied to concrete using single pixel analysis,\" Construction and Building Materials, 2010.","Akbar Darabi, Xavier Maldague, \"Neural network based defect detection and depth estimation in TNDE,\" NDT & E International, vol. 35, pp. 165-175, 2002.","C. Ibarra-Castanedo, F. Galmiche, A. Darabi, M. Pilla, M. Klein, A. Ziadi, S. Vallerand, J.-F. Pelletier, X. Maldague, \"Thermographic nondestructive evaluation: overview of recent progress,\" in SPIESociety of Photo-Optical Instrumentation Engineers, Procedures Thermosense XXV, 2003.","Hernán D. Benítez, Humberto Loaiza,Eduardo Caicedo,Clemente Ibarra- Castanedo,AbdelHakim Bendada,Xavier Maldague, \"Defect characterization in infrared non-destructive testing with learning machines,\" NDT & E International, vol. 42, pp. 630-643, 2009.","M. R. Clark, D. M. McCann, M. C. Forde, \"Application of infrared thermography to the non-destructive testing of concrete and masonry bridges,\" NDT & E International, vol. 36, pp. 265-275, 2003.","XAVIER P.V. MALDAGUE, Theory and Practice of Infrared Technology for Nondestructive Testing. Canada, 2001.","Manyong Choi, Kisoo Kang, Jeonghak Park, Wontae Kim, Koungsuk Kim, \"Quantitative determination of a subsurface defect of reference specimen by lock-in infrared thermography,\" NDT & E International, vol. 41, pp. 119-124, 2008.","S. Vallerand, X. Maldague \"Defect characterization in pulsed thermography: a statistical method compared with Kohonen and Perceptron neural networks,\" NDT & E International, vol. 33, pp. 307- 315, 2000. [10] U. Galietti, D. Palumbo, G. Calia and F. Ancona, \"New data analysis to evaluate defects in composite materials using microwaves thermography,\" presented at the 11th International Conference on Quantitative InfraRed Thermography, University of Naples Federico II, Naples, Italy, 2012. [11] Hongjoon Kim, Kyungyoung Jhang, Minjea Shin, Jaeyeol Kim \"A noncontact NDE method using a laser generated focused-Lamb wave with enhanced defect-detection ability and spatial resolution,\" NDT & E International, vol. 39, pp. 312-319, 2006. [12] J. Schlichting, Ch. Maierhofer, M. Kreutzbruck, \"Crack sizing by laser excited thermography,\" NDT & E International, vol. 45, pp. 133-140, 2012. [13] S. E. Burrows, S. Dixon, S.G. Pickering, T. Li, D.P. Almond, \"Thermographic detection of surface breaking defects using a scanning laser source,\" NDT & E International, vol. 44, pp. 589-596, 2011. [14] Teng Li, Darryl P. Almond, D.Andrew S. Rees, \"Crack imaging by scanning pulsed laser spot thermography,\" NDT & E International, vol. 44, pp. 216-225, 2011. [15] L. De Lorenzis and J. G. Teng, \"Near-surface mounted FRP reinforcement: An emerging technique for strengthening structures,\" Composites Part B: Engineering, vol. 38, pp. 119-143, 2007. [16] M. J. Chajes, et al., \"Durability of concrete beams externally reinforced with composite fabrics,\" Construction and Building Materials, vol. 9, pp. 141-148, 1995"]}

Ce travail présente une méthode inverse pour déterminer la diffusivité thermique et l’épaisseur du béton d’enrobage de deux poutres expérimentales, l’une en béton et l’autre en mortier. L’armature métallique centrale est sollicitée à l’aide d’un chauffage par induction et l’évolution des températures de surface est mesurée à l’aide d’une caméra infrarouge. Une modélisation numérique mettant en oeuvre un schéma ADI permet de résoudre l’équation de transfert thermique. Il est intégré à une procédure d’identification qui conduit à la détermination des paramètres d’épaisseur et de diffusivité thermique. Une étude de sensibilité montre que ces paramètres peuvent être déterminés simultanément durant la phase de chauffage de la barre. 29ème rencontre de l’AUGC Tlemcen (29-31 Mai 2011).

International audience

International audience