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Sfarra, Stefano

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Sfarra

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Stefano

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Université Laval. Département de génie électrique et de génie informatique

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ncf11899554

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Résultats de recherche

Voici les éléments 1 - 10 sur 13
  • PublicationRestreint
    Analysis of damage in hybrid composites subjected to ballistic impacts : an integrated non-destructive approach
    (Wiley, 2017-02-28) Maldague, Xavier; López, Fernando; Ibarra Castanedo, Clemente; Sarasini, Fabrizio; Sfarra, Stefano; Tirillò, Jacopo; Ferrante, Lucas; Perilli, Stefano; Paoletti, Domenica; Lampani; Barbero, Ever J.; Sánchez-Sáez
    In this chapter infrared (IR) vision has been used as non-destructive testing (NDT) method for the detection of damage occurred in hybrid composites subjected to high velocity impacts. In particular, carbon and basalt fibers have been used in the fabrication of the laminates with an intercalated and a sandwich-like structure. Near-infrared reflectography (NIRR) and infrared thermography (IRT) techniques have shown interesting complementarities, as well as the integrated image processing by using advanced algorithms, such as Partial-Least Square Thermography (PLST) and Principal Component Thermography (PCT). The laminates have been subjected to a long square pulse in order to make possible the acquisition of both the heating and the cooling phases, while the prediction of the damage due to the impacts has been evaluated by finite element (FE) analysis. Preliminary results inherent to the numerical simulation approach are reported. Finally, the damage state has been compared with a detailed fractographic analysis of the laminates’ cross-sections, and qualitatively estimated by segmentation algorithms, thus confirming the potential of the proposed integrated approach.
  • PublicationRestreint
    The use of flax fiber reinforced polymer (FFRP) composites in the externally reinforced structures for seismic retrofitting monitored by transient thermography and optical techniques
    (Wiley, 2017-03-01) Maldague, Xavier; Ibarra Castanedo, Clemente; Paoletti, Domenica; Bendada, Abdelhakim; Sfarra, Stefano
    Natural fibers constitute an interesting alternative to synthetic fibers for the production of composites due to their environmental and economic advantages. Even though their strength is on average lower compared to their synthetic counterparts, natural fibers such as flax, among other bast fibers (jute, kenaf, ramie, and hemp), are serious candidates for seismic retrofitting applications given that their mechanical properties are more suitable for dynamic loads. Strengthening of structures is performed by impregnating flax fiber reinforced polymers (FFRP) fabrics with epoxy resin and applying them to the component of interest, increasing in this way the load and deformation capabilities of the building, while preserving its stiffness and dynamic properties. The reinforced areas are however prompt to debonding if the fabrics are not properly mounted. Nondestructive testing is therefore required to verify that the fabric is installed uniformly and that there are no air gaps or foreign materials that could instigate debonding. In this Chapter, the use of active infrared thermography was investigated for the assessment of a laboratory specimen with artificial defects, an actual FFRP retrofitted beam, and a part of an external masonry wall. Results coming from the academic specimen were compared to digital speckle photography and holographic interferometry images
  • PublicationAccès libre
    Monitoring of jute/hemp fiber hybrid laminates by nondestructive testing techniques
    (De Gruyter, 2014-11-28) Maldague, Xavier; Ibarra Castanedo, Clemente; Santulli, Carlo; Sfarra, Stefano; Paoletti, Domenica
    Damage following static indentation of jute/hemp (50 wt.% total fiber content) hybrid laminates was detected by a number of nondestructive testing (NDT) techniques, in particular, near (NIR) and short-wave (SWIR) infrared reflectography and transmittography, infrared thermography (IRT), digital speckle photography (DSP), and holographic interferometry (HI), to discover and evaluate real defects in a laminate with a complex structure. A comparative study between thermographic data acquired in the mid- (MWIR) and long-wave infrared (LWIR) spectrum bands, by pulsed (PT) and square pulse (SPT) thermography, is reported and analyzed. A thermal simulation by COMSOL® Multiphysics (COMSOL Inc., Burlington, MA, USA) to validate the heating provided is also added. The robust SOBI (SOBI-RO) algorithm, available into the ICALAB Toolbox (BSI RIKEN ABSP Lab, Hirosawa, Japan) and operating in the MATLAB® (The MathWorks, Inc., Natick, MA, USA) environment, was applied on SPT data with results comparable to the ones acquired by several thermographic techniques. Finally, segmentation operators were applied both to the NIR/SWIR transmittography images and to a characteristic principal component thermography (PCT) image (EOFs) to visualize damage in the area surrounding indentation.
  • PublicationAccès libre
    Santa Maria di Collemaggio Church (L’Aquila, Italy) : historical reconstruction by non-destructive testing techniques
    (Taylor and Francis, 2014-02-28) Maldague, Xavier; Ibarra Castanedo, Clemente; Bendada, Abdelhakim; Ambrosini, Dario; Sfarra, Stefano; Paoletti, Domenica
    The main goal of this work was the non-destructive testing (NDT) of an ancient fresco (15th century) preserved in the Santa Maria di Collemaggio Church (L’Aquila, Italy) and damaged after the 2009 earthquake. Active infrared thermography (IRT), near-infrared (NIR) reflectography and ultraviolet imaging (UV) were used. In addition, the state of the fresco prior to the earthquake was analyzed by electronic speckle pattern interferometry (ESPI), digital speckle correlation (DSC), raking light, tap, and chemical NDT techniques. The use of these techniques was important for the monitoring of new damages and for a comparison between the results over the years. Square heating thermography (SHT) data were processed using principal component thermography (PCT) and pulsed phase thermography (PPT) algorithms, in order to improve the defects’ signature and to reduce the impact of non-uniform heating and emissivity variations due to the painting’s pigments. A multi-analysis approach, segmentation operators and a specific data correlation method emphasize the overall study of the fresco. Furthermore, the facade and the high altar area were inspected by passive thermography and ground-penetrating radar (GPR), respectively. In the present case, the combined use of NDT techniques was useful to fill in the gaps in the construction history of the building.
  • PublicationAccès libre
    Evaluation of defects in panel paintings using infrared, optical and ultrasonic techniques
    (British Institute of Non-Destructive Testing, 2012-01-01) Avdelidis, Nicolas P.; Theodorakeas, Panagiotis; Maldague, Xavier; Ibarra Castanedo, Clemente; Bendada, Abdelhakim; Paoletti, Alfonso; Sfarra, Stefano; Paoletti, Domenica; Hrissagis, Kostas; Koui, Maria
    The increasing deterioration of panel paintings can be due to physical processes that take place during exhibition or transit, or as a result of temperature and humidity fluctuations within a building, church or museum. In response to environmental alterations, a panel painting can expand or contract and a new equilibrium state is eventually reached. These adjustments though, are usually accompanied by a change in shape in order to accommodate to the new conditions. In this work, a holographic method for detecting detached regions and micro-cracks is described. Some of these defects are confirmed by Thermographic Signal Reconstruction (TSR) technique. In addition, Pulsed Phase Thermography (PPT) and Principal Component Thermography (PCT) allow to identify with greater contrast two artificial defects in Mylar which are crucial to understand the topic of interest: the discrimination between defect materials. Finally, traditional contact ultrasounds applications, are widely applied for the evaluation of the wood quality in several characterization procedures. Inspecting the specimen from the front side, the natural and artificial defects of the specimen are confirmed. Experimental results derived by the application of the integrated methods on an Italian panel painting reproduction, called The Angel specimen, are presented. The main advantages that these techniques can offer to the conservation and restoration of artworks are emphasized.
  • PublicationAccès libre
    Surface and subsurface defects detection in impacted composite materials made by natural fibers, using nondestructive testing methods
    (Scientific & Academic Publishing, 2014-01-01) Avdelidis, Nicolas P.; Maldague, Xavier; Ibarra Castanedo, Clemente; Santulli, Carlo; Bendada, Abdelhakim; Theodorakeas, Panagiotis; Sfarra, Stefano; Paoletti, Domenica; Koui, Maria
    In the present study, infrared vision and optical nondestructive testing (NDT) techniques were applied for the evaluation of emerging defects after artificially impacting composite materials reinforced with natural fibers. The samples were manufactured using wool felts and jute fibers inserted in an epoxy matrix. Infrared vision was applied by means of pulsed thermography (PT) and square pulsed thermography (SPT), evaluating two different thermal stimulation procedures; while the algorithms referred to as principal component thermography (PCT) and pulsed phase thermography (PPT) were used in order to enhance the information retrieval from the respective thermographic inspections. For comparison purposes, near-infrared reflectography (NIRR) and transmittography (NIRT), as well as laser speckle imaging techniques were also included. Additionally, ultraviolet (UV) imaging technique was used on the laminates both as complementary approach and as reference for future inspections. Two particular zones highlighted by the latter technique were characterized using an XRF spectrophotometer revealing a reverse concentration of the Al, Si and Cl elements. The results produced from the above comparative study confirmed the synergy of the applied techniques and further indicated that the methodology followed in the present research work can be considered as an innovative approach for the characterization of eco-friendly laminates after an impact loading.
  • PublicationAccès libre
    How to reveal subsurface defects in Kevlar® composite materials after an impact loading using infrared vision and optical NDT techniques?
    (Elsevier, 2013-03-07) Talmy, Étienne; Maldague, Xavier; Ibarra Castanedo, Clemente; Paoletti, Domenica; Bendada, Abdelhakim; Genest, Marc; Rott, Sébastien; Sfarra, Stefano
    An integrated system between infrared vision and optical non-destructive testing techniques can be considered a viable, robust and reliable approach for both aerospace manufacturing and in-service inspections. In this paper, infrared vision is applied in different spectral bands on two impacted panels made of aramid–phenolic composite by applying two different methods, respectively: (1) near and short-wave infrared reflectography and transmittography, and (2) mid-wave active infrared thermography. Furthermore, optical methods, namely digital speckle photography and holographic interferometry, are used as well to highlight the damages due to the impacts on the samples. Some techniques provide more straightforward detection capabilities than others for different defect types.
  • PublicationAccès libre
    Holographic interferometry (HI), infrared Vision and X-Ray fluorescence (XRF) spectroscopy for the assessment of painted wooden statues : a new integrated approach
    (Springer, 2013-09-03) Maldague, Xavier; Ibarra Castanedo, Clemente; Ridolfi, Stefano; Sfarra, Stefano; Cerichelli, Giorgio; Ambrosini, Dario; Paoletti, Domenica
    Wood has been routinely employed in decorative arts, as well as in sculptures and paintings (support) during the Middle Ages, because of its unique aesthetic virtues. It may safely be assumed that wood, as a material for monumental sculpture, was much more commonly employed in the mediaeval period than existing examples would seem to indicate (Bulletin of the metropolitan Museum of Art, 2013). Wood is easily obtainable; it could be carved and put in place with less difficulty than stone, it is chemically stable when dry, and its surface offers a compatible substrate for paint application. However, the use of wood is not without pitfalls, and requires an understanding of its anisotropic and hygroscopic nature. It is also dimensionally unstable and subject to deterioration by fungi and insects. Moisture-related dimensional changes are certainly among the most challenging problems in painting conservation. With the purpose of preventing important damages, the use of non-or microdestructive testing (NDT) techniques is undoubtedly of paramount interest for painted wooden statues of great value. This work has a threefold purpose: (1) to validate the effectiveness of an integrated approach using near-infrared (NIR) reflectography, square pulse thermography (SPT), and holographic interferometry (HI) techniques for discovering old repairs and/or inclusions of foreign materials in a wooden structure, (2) to confirm and approximately date the restoration carried out by x-ray fluorescence (XRF) spectroscopy and energy-dispersive x-ray spectroscopy (EDS) (that is assembled with a scanning electron microscopy—SEM) techniques, and (3) to combine into a multidisciplinary approach two quantitative NDT results coming from optical and thermographic methods. The subject of the present study was a statue named “Virgin with her Child” (XIV century), whose origins are mysterious and not properly documented.
  • PublicationAccès libre
    Non-destructive testing techniques to help the restoration of frescoes
    (King Fahd University of Petroleum and Minerals, 2014-03-06) Maldague, Xavier; Ibarra Castanedo, Clemente; Ambrosini, Dario; Bendada, Abdelhakim; Paoletti, Domenica; Sfarra, Stefano
    Among the several issues to be considered during fresco’s restoration, the understanding of the effectiveness of the intervention, the identification of the main chemical elements used in previous restorations and the attention to weak areas of the building structure, adjacent to frescoes, are of paramount importance. This work describes an integrated, non-destructive testing approach focusing on these three main issues. In particular, two frescoes of Giacomo Farelli are analyzed herein. These artworks were affected by a strong earthquake in 2009, which had a heavy impact on several cultural heritage objects in L’Aquila (Italy), including on the Santa Maria della Croce di Roio Church (1625), where these two frescoes are located. One of the frescoes, which underwent a restoring before the quake, was previously tested by electronic speckle pattern interferometry (ESPI) before and after the restoration. These previous results are compared with new measurements carried out after the 2009 earthquake using infrared thermography (IRT). The combined approach, ESPI-IRT, clearly highlighted that the structure of the frescoes was significantly affected by the earthquake, since the old subsurface cracks, restored before 2009, were once again evident after the earthquake. In addition, the presence of a subsurface niche containing an ancient statue, also detected by means of IRT, might contribute to increase the severity of the damages. Finally, the joint examination of these frescoes using near-infrared reflectography and X-ray diffractometry was crucial to confirm the presence of a radioactive chemical element in the wall painting.
  • PublicationAccès libre
    Integrated approach between pulsed thermography, near-infrared reflectography and sandwich holography for wooden panel paintings advanced monitoring
    (Pleiades Publishing : Nauka/Interperiodica, 2011-06-28) Maldague, Xavier; Ibarra Castanedo, Clemente; Ambrosini, Dario; Bendada, Abdelhakim; Paoletti, Domenica; Sfarra, Stefano
    The durability of an exterior finish is affected by the characteristics of the wood. Satisfactory finish life is usually more difficult to achieve on woods of higher density. All wood shrinks as it loses moisture and swells as it absorbs moisture, but some species are more stable than others. Species that shrink and swell the most cause more stress on paint films than woods that are more stable [1]. To this end, let us recall that a painting on wood can be considered as a layered structure: The wood support is coated with a number of superposed priming layers made from mixtures of gesso and glue. A frequent fault resulting from such a system is the formation of detached regions inside the layered structure caused by the shrinkage process of the wood support [2]. Obviously, wood deteriorates more rapidly in warm, humid regions with respect to cool or dry places [3]. The influence of wood conditions on surface coatings is a critical point that should be monitored and that depends on environmental parameters such as microclimate. To prevent and control the effects, keeping costs down, a non-destructive monitoring of wood support behavior under thermal stress is needed. In this work, an integrated approach based on traditional and innovative (HI, PT and NIR) techniques was conducted on a primed support of poplar wood with a complex-shape surface containing areas of artificial defects at several depths due to the influence of the support on the various layers. The obtained results could be arranged, if integrated into a multidisciplinary approach, in order to define and design the conservation of the wooden artifacts.