The Experts below are selected from a list of 4161 Experts worldwide ranked by ideXlab platform
Xiaoyan Liu - One of the best experts on this subject based on the ideXlab platform.
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numerical optimizing and experimental evaluation of stepwise rapid high pressure microwave curing carbon fiber epoxy composite Repair patch
Composite Structures, 2019Co-Authors: Xiaoyan Liu, Dacheng QiuAbstract:Abstract Numerical models of multi-layer composite laminates with various fiber orientations and fiber layers were investigated under adhesively Bonded Repair condition by ABAQUS. Stress intensity factors (SIF) of Bonded structure systems were calculated by J integral method. Results indicated that composite laminate with [90/90/90] fiber orientation and three fiber layers exhibited the lowest numerical SIF value. The laminates reinforced by carbon fiber with corresponding orientation were experimentally prepared in a two-step high-pressure microwave curing and traditional thermal curing methods on the basis of simulated results, respectively. Mechanical and curing properties of laminates prepared by two curing methods were characterized and compared by means of tensile tests and differential scanning calorimetry (DSC). In comparison to the thermal curing method, the laminate can be prepared more effectively by means of microwave curing method, and the laminate with [90/90/90] fiber orientation and three fiber layers showed the optimal static mechanical performance and the highest curing degree due to the synergistic effect of dipolar induced effect and heating effect generated by microwave, which was in well agreement with the results of numerical simulation.
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Bonded Repair optimization of cracked aluminum alloy plate by microwave cured carbon aramid fiber epoxy sandwich composite patch
Materials, 2019Co-Authors: Xiaoyan LiuAbstract:Fiber-reinforced epoxy sandwich composites, which were designed as the Bonded Repair patches to better recover the mechanical performance of a central cracked aluminum alloy plate, were layered by carbon and aramid fiber layers jointly and cured by microwave method in this study. The static tensile and bending properties of both carbon-aramid fiber/epoxy sandwich composite patches and the cracked aluminum alloy plates after Bonded Repair were systematically investigated. By comparing the mechanical performance with traditional single carbon-fiber-reinforced composite patches, it can be found that the bending performance of carbon-aramid fiber sandwich composite patches was effectively improved after incorporation of flexible aramid fiber layers into the carbon fiber layers, but the tensile strength of sandwich composite patches was weakened to some extent. Especially, the sandwich patches with 3 fiber layers exhibited better tensile and bending performance in comparison to patches of 5 and 7 fiber layers. The optimized 3-layer carbon-aramid fiber sandwich patch Repaired plate recovered 86% and 190% of the tensile and bending performance in comparison to the uncracked ones, respectively, showing a considerable Repair majorization effect for the cracked aluminum alloy plate.
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Bonded Repair Optimization of Cracked Aluminum Alloy Plate by Microwave Cured Carbon-Aramid Fiber/Epoxy Sandwich Composite Patch
MDPI AG, 2019Co-Authors: Xiaoyan LiuAbstract:Fiber-reinforced epoxy sandwich composites, which were designed as the Bonded Repair patches to better recover the mechanical performance of a central cracked aluminum alloy plate, were layered by carbon and aramid fiber layers jointly and cured by microwave method in this study. The static tensile and bending properties of both carbon-aramid fiber/epoxy sandwich composite patches and the cracked aluminum alloy plates after Bonded Repair were systematically investigated. By comparing the mechanical performance with traditional single carbon-fiber-reinforced composite patches, it can be found that the bending performance of carbon-aramid fiber sandwich composite patches was effectively improved after incorporation of flexible aramid fiber layers into the carbon fiber layers, but the tensile strength of sandwich composite patches was weakened to some extent. Especially, the sandwich patches with 3 fiber layers exhibited better tensile and bending performance in comparison to patches of 5 and 7 fiber layers. The optimized 3-layer carbon-aramid fiber sandwich patch Repaired plate recovered 86% and 190% of the tensile and bending performance in comparison to the uncracked ones, respectively, showing a considerable Repair majorization effect for the cracked aluminum alloy plate
Sp G Pantelakis - One of the best experts on this subject based on the ideXlab platform.
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the effects of manufacturing induced and in service related bonding quality reduction on the mode i fracture toughness of composite Bonded joints for aeronautical use
Composites Part B-engineering, 2013Co-Authors: D N Markatos, K I Tserpes, E Rau, S Markus, B Ehrhart, Sp G PantelakisAbstract:Abstract The scope of the present work is to investigate the possible effects of manufacturing and in-service induced reduction of bonding quality on the mechanical performance of composite Bonded joints appearing in aeronautical applications, due to defects that cannot be detected sufficiently by means of conventional NDT. To this end, an experimental program has been conducted to measure mode-I interlaminar fracture toughness of adhesively Bonded CFRP laminates. Five different representative scenarios have been considered; namely, poor curing of the adhesive, release agent contamination and moisture uptake by the composite substrates, which may occur during manufacturing of the joints, as well as Skydrol contamination and thermal degradation of the composite substrates, which are related to in-service life and could affect an adhesively Bonded Repair. Eight specimens for each scenario were tested. To assess the effects of each scenario, the experimental results have been compared with relative measurements taken from a set of reference specimens. Prior to mechanical testing, and the conventional NDT techniques, ultrasound C-scan and X-ray tests have been conducted to assess the quality of the bondline. All scenarios considered in the present study have been found to have an effect on the mode-I fracture toughness of the composite Bonded joints. It was also shown that conventional NDT, such as ultrasonic and X-ray inspection, are not capable to sufficiently detect the defects resulting from the specific scenarios considered and being responsible for the reduction of joint’s performance.
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the effects of manufacturing induced and in service related bonding quality reduction on the mode i fracture toughness of composite Bonded joints for aeronautical use
Composites Part B-engineering, 2013Co-Authors: D N Markatos, K I Tserpes, S Markus, B Ehrhart, Sp G PantelakisAbstract:Abstract The scope of the present work is to investigate the possible effects of manufacturing and in-service induced reduction of bonding quality on the mechanical performance of composite Bonded joints appearing in aeronautical applications, due to defects that cannot be detected sufficiently by means of conventional NDT. To this end, an experimental program has been conducted to measure mode-I interlaminar fracture toughness of adhesively Bonded CFRP laminates. Five different representative scenarios have been considered; namely, poor curing of the adhesive, release agent contamination and moisture uptake by the composite substrates, which may occur during manufacturing of the joints, as well as Skydrol contamination and thermal degradation of the composite substrates, which are related to in-service life and could affect an adhesively Bonded Repair. Eight specimens for each scenario were tested. To assess the effects of each scenario, the experimental results have been compared with relative measurements taken from a set of reference specimens. Prior to mechanical testing, and the conventional NDT techniques, ultrasound C-scan and X-ray tests have been conducted to assess the quality of the bondline. All scenarios considered in the present study have been found to have an effect on the mode-I fracture toughness of the composite Bonded joints. It was also shown that conventional NDT, such as ultrasonic and X-ray inspection, are not capable to sufficiently detect the defects resulting from the specific scenarios considered and being responsible for the reduction of joint’s performance.
D N Markatos - One of the best experts on this subject based on the ideXlab platform.
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the effects of manufacturing induced and in service related bonding quality reduction on the mode i fracture toughness of composite Bonded joints for aeronautical use
Composites Part B-engineering, 2013Co-Authors: D N Markatos, K I Tserpes, E Rau, S Markus, B Ehrhart, Sp G PantelakisAbstract:Abstract The scope of the present work is to investigate the possible effects of manufacturing and in-service induced reduction of bonding quality on the mechanical performance of composite Bonded joints appearing in aeronautical applications, due to defects that cannot be detected sufficiently by means of conventional NDT. To this end, an experimental program has been conducted to measure mode-I interlaminar fracture toughness of adhesively Bonded CFRP laminates. Five different representative scenarios have been considered; namely, poor curing of the adhesive, release agent contamination and moisture uptake by the composite substrates, which may occur during manufacturing of the joints, as well as Skydrol contamination and thermal degradation of the composite substrates, which are related to in-service life and could affect an adhesively Bonded Repair. Eight specimens for each scenario were tested. To assess the effects of each scenario, the experimental results have been compared with relative measurements taken from a set of reference specimens. Prior to mechanical testing, and the conventional NDT techniques, ultrasound C-scan and X-ray tests have been conducted to assess the quality of the bondline. All scenarios considered in the present study have been found to have an effect on the mode-I fracture toughness of the composite Bonded joints. It was also shown that conventional NDT, such as ultrasonic and X-ray inspection, are not capable to sufficiently detect the defects resulting from the specific scenarios considered and being responsible for the reduction of joint’s performance.
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the effects of manufacturing induced and in service related bonding quality reduction on the mode i fracture toughness of composite Bonded joints for aeronautical use
Composites Part B-engineering, 2013Co-Authors: D N Markatos, K I Tserpes, S Markus, B Ehrhart, Sp G PantelakisAbstract:Abstract The scope of the present work is to investigate the possible effects of manufacturing and in-service induced reduction of bonding quality on the mechanical performance of composite Bonded joints appearing in aeronautical applications, due to defects that cannot be detected sufficiently by means of conventional NDT. To this end, an experimental program has been conducted to measure mode-I interlaminar fracture toughness of adhesively Bonded CFRP laminates. Five different representative scenarios have been considered; namely, poor curing of the adhesive, release agent contamination and moisture uptake by the composite substrates, which may occur during manufacturing of the joints, as well as Skydrol contamination and thermal degradation of the composite substrates, which are related to in-service life and could affect an adhesively Bonded Repair. Eight specimens for each scenario were tested. To assess the effects of each scenario, the experimental results have been compared with relative measurements taken from a set of reference specimens. Prior to mechanical testing, and the conventional NDT techniques, ultrasound C-scan and X-ray tests have been conducted to assess the quality of the bondline. All scenarios considered in the present study have been found to have an effect on the mode-I fracture toughness of the composite Bonded joints. It was also shown that conventional NDT, such as ultrasonic and X-ray inspection, are not capable to sufficiently detect the defects resulting from the specific scenarios considered and being responsible for the reduction of joint’s performance.
Barus Matthias - One of the best experts on this subject based on the ideXlab platform.
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Signatures thermiques d’interfaces collées pour la réparation des structures primaires en matériaux composites
2016Co-Authors: Barus MatthiasAbstract:This PhD work intends to contribute to the characterization of structural Bonded Repair quality of primary composite structures using InfraRed Thermography (IRT). Generally, in this case, the parent structure and the Repair patch are both made of carbon-epoxy and are linked together by an epoxy adhesive. Such Repair configuration then leads to a weak property contrast between the parts of the Repaired assembly. Therefore, the non-destructive analysis of the bonding quality remains dificult and represents the very challenging issue of this study. In this way, a new specific Non Destructive Testing (NDT) procedure has been firstly developed that allows physically consistent numerical model of the thermal problem and a good correlation with experimental data. Additionally, it is proposed to use relevant additives that modify the thermal properties of the glue joint in order to improve the detection of bond defects
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Signatures thermiques d'interfaces collées pour la réparation des structures primaires en matériaux composites
2016Co-Authors: Barus MatthiasAbstract:L'ambition de cette thèse est de contribuer à la caractérisation de la qualité des réparations des structures composites primaires en carbone par collage structural en s'appuyant pour cela sur la technique de la Thermographie InfraRouge (TIR). Le caractère ténu de la différence de comportement entre les parties constitutives de l'assemblage réparé (parent et patch en carbone-époxyde, adhésif époxyde) et donc la difficulté de capter la réponse thermique du joint collé constituent les enjeux principaux de ce travail. A cette fin, une procédure expérimentale de Contrôle Non Destructif (CND) a tout d'abord été spécifiquement mise au point pour cette étude, permettant une modélisation numérique physiquement cohérente du problème thermique ainsi qu'une bonne concordance avec les champs de température mesurés. Le travail propose par ailleurs une piste complémentaire visant à modifier les propriétés thermiques intrinsèques du joint à l'aide d'additifs dont la signature infrarouge permet d'identifier plus nettement des défauts de collage.This PhD work intends to contribute to the characterization of structural Bonded Repair quality of primary composite structures using InfraRed Thermography (IRT). Generally, in this case, the parent structure and the Repair patch are both made of carbon-epoxy and are linked together by an epoxy adhesive. Such Repair configuration then leads to a weak property contrast between the parts of the Repaired assembly. Therefore, the non-destructive analysis of the bonding quality remains difficult and represents the very challenging issue of this study. In this way, a new specific Non Destructive Testing (NDT) procedure has been firstly developed that allows physically consistent numerical model of the thermal problem and a good correlation with experimental data. Additionally, it is proposed to use relevant additives that modify the thermal properties of the glue joint in order to improve the detection of bond defects
Xinlin Qing - One of the best experts on this subject based on the ideXlab platform.
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A Real-time Electromechanical Impedance-based Active Monitoring for Composite Patch Bonded Repair Structure
Composite Structures, 2019Co-Authors: Yishou Wang, Xinlin QingAbstract:Abstract With the increase of serving time, the metallic primary structures are extremely likely to risk structural failures due to aging and external loads. Composite patch Bonded Repair offers an effective technique for recovering the ultimate load-bearing capability of the structure. Disbond between the composite patch and the substrate is a typical failure mode that severely reduces the structural stiffness and strength of Repair region. In this paper, a combining active monitoring scheme is proposed based on electromechanical impedance (EMI) and coupling constitutive equations. Two statistical damage indices (DIs), root mean square deviation (RMSD) and mean absolute percentage deviation (MAPD), are adopted for locating the disbond and evaluating its severity based on extracted signatures. Experiments on the Repair structure with a 3 × 3 sensors array are performed to monitor the disbond between Repair patch and substrate. The experimental results show that both disbond locations and severities on the bondline can be monitored efficaciously with the proposed active monitoring scheme.
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a real time active smart patch system for monitoring the integrity of Bonded Repair on an aircraft structure
Smart Materials and Structures, 2006Co-Authors: Xinlin Qing, Shawn J Beard, Amrita Kumar, Robert HannumAbstract:There currently exists a need to develop a cost-effective, in-service structural health monitoring (SHM) system for determining the initial quality of a Bonded Repair and assessing the long-term durability of the Bonded Repair on an aircraft structure. In this paper, a real-time active smart patch system (SPS) based on SMART layer technology is introduced for monitoring the integrity of Bonded Repairs. First, an overview of the SPS is given for typical metal and composite Repairs. To illustrate the capability of the SPS, three applications are presented: (1) monitoring of the cure progress of the Bonded Repair adhesive, (2) detection of the initial artificial disbond between the composite patch and the metal structure, and (3) monitoring of damage in and around a Bonded Repair during fatigue cycling. The results show that, through the use of a real-time active SPS approach of using sensors placed in, on or around the Repair, the initial quality and long-term durability of the Repair can be evaluated and monitored.
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in situ monitoring of the integrity of Bonded Repair patches on aircraft and civil infrastructures
Advanced sensor technologies for nondestructive evaluation and structural health monitoring. Conference, 2006Co-Authors: Amrita Kumar, Xinlin Qing, Shawn J Beard, Dennis P Roach, Robert HannumAbstract:Monitoring the continued health of aircraft subsystems and identifying problems before they affect airworthiness has been a long-term goal of the aviation industry. Because in-service conditions and failure modes experienced by structures are generally complex and unknown, conservative calendar-based or usage-based scheduled maintenance practices are overly time-consuming, labor-intensive and expensive. Metal structures such as helicopters and other transportation systems are likely to develop fatigue cracks under cyclic loads and corrosive service environments. Early detection of cracks is a key element to prevent catastrophic failure and prolong structural life. Furthermore, as structures age, maintenance service frequency and costs increase while performance and availability decrease. Current non-destructive inspection (NDI) techniques that can potentially be used for this purpose typically involve complex, time-intensive procedures, which are labor-intensive and expensive. Most techniques require access to the damaged area on at least one side, and sometimes on both sides. This can be very difficult for monitoring of certain inaccessible regions. In those cases, inspection may require removal of access panels or even structural disassembly. Once access has been obtained, automated inspection techniques likely will not be practical due to the bulk of the required equipment. Results obtained from these techniques may also be sensitive to the sweep speed, tool orientation, and downward pressure. This can be especially problematic for hand-held inspection tools where none of these parameters is mechanically controlled. As a result, data can vary drastically from one inspection to the next, from one technician to the next, and even from one sweep to the next. Structural health monitoring (SHM) offers the promise of a paradigm shift from schedule-driven maintenance to condition-based maintenance (CBM) of assets. Sensors embedded permanently in aircraft safety critical structures that can monitor damage can provide for improved reliability and streamlining of aircraft maintenance. Early detection of damage such as fatigue crack initiation can improve personnel safety and prolong service life. This paper presents the testing of an acousto-ultrasonic piezoelectric sensor based structural health monitoring system for real-time monitoring of fatigue cracks and disbonds in Bonded Repairs. The system utilizes a network of distributed miniature piezoelectric sensors/actuators embedded on a thin dielectric carrier film, to query, monitor and evaluate the condition of a structure. The sensor layers are extremely flexible and can be integrated with any type of metal or composite structure. Diagnostic signals obtained from a structure during structural monitoring are processed by a portable diagnostic unit. With appropriate diagnostic software, the signals can be analyzed to ascertain the integrity of the structure being monitored. Details on the system, its integration and examples of detection of fatigue crack and disbond growth and quantification for Bonded Repairs will be presented here.