30 juin 2020
Prediction of elastic moduli and ultimate strength of fiber/yarn-reinforced elastic–plastic matrix using Fourier series approach and cuboidal/wedge sub-volumes - ScienceDirect
Prediction of elastic moduli and ultimate strength of fiber/yarn-reinforced elastic–plastic matrix using Fourier series approach and cuboidal/wedge sub-volumes - ScienceDirect: Homogenization of mechanical properties of a heterogeneous material using analytical/semi-analytical micromechanics approaches is computationally less expensive than that through numerical techniques. However, analytical methods cannot be easily applied to a complex distribution of the microstructure in a unit cell (or a representative volume element). Here, we alleviate this by accommodating cuboidal and wedge sub-volumes in the Fourier series approach (FSA). This is akin to using penta-and hexa-hedral elements to discretize the geometry in 3-dimensional finite element analysis (FEA)......
26 juin 2020
Contrat doctoral 2020/2023 Formulaire de candidature
Contrat doctoral 2020/2023 Formulaire de candidature
Les énergies marines renouvelables dans leur ensemble (hydroliennes, éoliennes en mer, …) font partie des objectifs de spécialisation intelligente de plusieurs régions en France et dans le monde. Au premier rang de cet axe d’innovation, la région Sud PACA revendique une position de leader autour de la technologie plus ciblée de l’éolien off-shore flottant. Dans ce contexte, l’université de Toulon, à travers son pôle de recherche transverse, Mer Environnement Développement Durable, a initié des amorces de projets de recherche pour identifier les verrous à lever dans ce secteur technologique : EOLEMED. L’un d’eux concerne spécifiquement la durée de vie de ces machines prévue pour 20 à 30 ans de fonctionnement en environnement marin plus ou moins agressif (UV, humidité, etc,…). L’essentiel du vieillissement des matériaux qui reste à maîtriser sur cette échelle de temps [1,2], se concentre sur les pales des éoliennes en matériaux composites qui atteignent 80 m et surtout sur leurs revêtements de protection. En effet, la durabilité de ces revêtements barrières est primordiale pour protéger l’ensemble de la structure. On connait désormais assez bien les mécanismes (chimiques, physiques…) conduisant à la perte des propriétés. En revanche, le prolongement de leur durée de vie pour atteindre 30 années de fonctionnement (par l’utilisation de matériaux auto cicatrisants), et le développement de résines biosourcées offrant un meilleur compromis entre cout énergétique et propriétés d’usage, l’évaluation de leur endommagement in situ au sein même de la structure dans laquelle ils sont confinés restent des questions ouvertes.
Les énergies marines renouvelables dans leur ensemble (hydroliennes, éoliennes en mer, …) font partie des objectifs de spécialisation intelligente de plusieurs régions en France et dans le monde. Au premier rang de cet axe d’innovation, la région Sud PACA revendique une position de leader autour de la technologie plus ciblée de l’éolien off-shore flottant. Dans ce contexte, l’université de Toulon, à travers son pôle de recherche transverse, Mer Environnement Développement Durable, a initié des amorces de projets de recherche pour identifier les verrous à lever dans ce secteur technologique : EOLEMED. L’un d’eux concerne spécifiquement la durée de vie de ces machines prévue pour 20 à 30 ans de fonctionnement en environnement marin plus ou moins agressif (UV, humidité, etc,…). L’essentiel du vieillissement des matériaux qui reste à maîtriser sur cette échelle de temps [1,2], se concentre sur les pales des éoliennes en matériaux composites qui atteignent 80 m et surtout sur leurs revêtements de protection. En effet, la durabilité de ces revêtements barrières est primordiale pour protéger l’ensemble de la structure. On connait désormais assez bien les mécanismes (chimiques, physiques…) conduisant à la perte des propriétés. En revanche, le prolongement de leur durée de vie pour atteindre 30 années de fonctionnement (par l’utilisation de matériaux auto cicatrisants), et le développement de résines biosourcées offrant un meilleur compromis entre cout énergétique et propriétés d’usage, l’évaluation de leur endommagement in situ au sein même de la structure dans laquelle ils sont confinés restent des questions ouvertes.
US20200158664A1 - Dual scan method for detecting a fibre misalignment in an elongated structure - Google Patents
US20200158664A1 - Dual scan method for detecting a fibre misalignment in an elongated structure - Google Patents
The present disclosure relates to a method for detecting a fibre misalignment in an elongated structure, such as a wind turbine blade component. The elongated structure has a length along a longitudinal direction and comprises a plurality of stacked reinforcing fibre layers. The plurality of fibre layers comprises fibres having an orientation aligned, unidirectionally, substantially in the longitudinal direction. The method comprises scanning a surface of the elongated structure for identifying one or more surface irregularities, selecting one or more regions of interest comprising said one or more surface irregularities, examining said region of interest using penetrating radiation, and determining a position and/or size of the fibre misalignment based on said examining step.
The present disclosure relates to a method for detecting a fibre misalignment in an elongated structure, such as a wind turbine blade component. The elongated structure has a length along a longitudinal direction and comprises a plurality of stacked reinforcing fibre layers. The plurality of fibre layers comprises fibres having an orientation aligned, unidirectionally, substantially in the longitudinal direction. The method comprises scanning a surface of the elongated structure for identifying one or more surface irregularities, selecting one or more regions of interest comprising said one or more surface irregularities, examining said region of interest using penetrating radiation, and determining a position and/or size of the fibre misalignment based on said examining step.
18 juin 2020
Consultation : fabrication, commercialisation, maintenance de matériels innovants pour essais en laboratoire | Cerema
Consultation : fabrication, commercialisation, maintenance de matériels innovants pour essais en laboratoire | Cerema
Le Cerema et l’Université Gustave Eiffel lancent une première consultation pour la fabrication, la commercialisation et la maintenance de matériels co-développés vendus sous la marque mlpc®, destinés à réaliser des essais en laboratoire sur des matériaux utilisés pour la construction et la maintenance d’infrastructures. Une future consultation portera sur les matériels d'essais sur le terrain, afin de connaître les caractéristiques des sols supports ou des infrastructures réalisées.
Le Cerema et l’Université Gustave Eiffel lancent une première consultation pour la fabrication, la commercialisation et la maintenance de matériels co-développés vendus sous la marque mlpc®, destinés à réaliser des essais en laboratoire sur des matériaux utilisés pour la construction et la maintenance d’infrastructures. Une future consultation portera sur les matériels d'essais sur le terrain, afin de connaître les caractéristiques des sols supports ou des infrastructures réalisées.
17 juin 2020
METHODS FOR THERMAL WELDING OF WIND TURBINE BLADES - Alliance for Sustainable Energy, LLC
METHODS FOR THERMAL WELDING OF WIND TURBINE BLADES - Alliance for Sustainable Energy, LLC
Disclosed herein are methods, devices, and systems for manufacturing wind turbine blades which in some instances require using new blade joint designs. The blade joint designs described herein may allow for contact in places where welds will be made, which allows for existing manufacturing tolerances to be used while still enabling the use of thermal welding for wind turbine blades.
Disclosed herein are methods, devices, and systems for manufacturing wind turbine blades which in some instances require using new blade joint designs. The blade joint designs described herein may allow for contact in places where welds will be made, which allows for existing manufacturing tolerances to be used while still enabling the use of thermal welding for wind turbine blades.
12 juin 2020
Design and Integration of a Wireless Stretchable Multimodal Sensor Network in a Composite Wing
Design and Integration of a Wireless Stretchable Multimodal Sensor Network in a Composite Wing
This article presents the development of a stretchable sensor network with high signal-to-noise ratio and measurement accuracy for real-time distributed sensing and remote monitoring. The described sensor network was designed as an island-and-serpentine type network comprising a grid of sensor “islands” connected by interconnecting “serpentines.” A novel high-yield manufacturing process was developed to fabricate networks on recyclable 4-inch wafers at a low cost. The resulting stretched sensor network has 17 distributed and functionalized sensing nodes with low tolerance and high resolution. The sensor network includes Piezoelectric (PZT), Strain Gauge (SG), and Resistive Temperature Detector (RTD) sensors. The design and development of a flexible frame with signal conditioning, data acquisition, and wireless data transmission electronics for the stretchable sensor network are also presented.....
This article presents the development of a stretchable sensor network with high signal-to-noise ratio and measurement accuracy for real-time distributed sensing and remote monitoring. The described sensor network was designed as an island-and-serpentine type network comprising a grid of sensor “islands” connected by interconnecting “serpentines.” A novel high-yield manufacturing process was developed to fabricate networks on recyclable 4-inch wafers at a low cost. The resulting stretched sensor network has 17 distributed and functionalized sensing nodes with low tolerance and high resolution. The sensor network includes Piezoelectric (PZT), Strain Gauge (SG), and Resistive Temperature Detector (RTD) sensors. The design and development of a flexible frame with signal conditioning, data acquisition, and wireless data transmission electronics for the stretchable sensor network are also presented.....
5 juin 2020
Long-term durability of offshore wind turbine composite blades based on nonlinear load behavior due to pitch movement | SpringerLink
Long-term durability of offshore wind turbine composite blades based on nonlinear load behavior due to pitch movement | SpringerLink
This study proposes a fatigue life prediction method for offshore wind turbines consisting of a fatigue load calculation method that accounts for external environmental factors and system interaction, as well as a fatigue stress spectrum calculation method based on the control strategy. First, we conducted an integrated load analysis considering both external environmental factors and system design characteristics to obtain the ultimate load for flapwise, edgewise, and spanwise directions of the blade. We then applied the ultimate load to the blade finite element model to identify the fatigue critical locations (FCLs) of the blade. Subsequently, we calculated force/moment-local stress relationships considering the applied load magnitude and its change in location according to the control strategy. A 10-min wind speed history was applied to these stress relationships to obtain the unit fatigue stress spectrum at the FCLs. This was then combined with the fatigue resistance of the material to obtain the unit fatigue damage at the FCLs. Finally, we applied the statistical wind speed data at a specific site to the unit fatigue damage to calculate the fatigue damage and life. Based on these results, we evaluated the effect of the loads in each blade direction on the fatigue life of a composite blade.
This study proposes a fatigue life prediction method for offshore wind turbines consisting of a fatigue load calculation method that accounts for external environmental factors and system interaction, as well as a fatigue stress spectrum calculation method based on the control strategy. First, we conducted an integrated load analysis considering both external environmental factors and system design characteristics to obtain the ultimate load for flapwise, edgewise, and spanwise directions of the blade. We then applied the ultimate load to the blade finite element model to identify the fatigue critical locations (FCLs) of the blade. Subsequently, we calculated force/moment-local stress relationships considering the applied load magnitude and its change in location according to the control strategy. A 10-min wind speed history was applied to these stress relationships to obtain the unit fatigue stress spectrum at the FCLs. This was then combined with the fatigue resistance of the material to obtain the unit fatigue damage at the FCLs. Finally, we applied the statistical wind speed data at a specific site to the unit fatigue damage to calculate the fatigue damage and life. Based on these results, we evaluated the effect of the loads in each blade direction on the fatigue life of a composite blade.
4 juin 2020
Stiffening offshore composite wind-blades bonding joints by carbon nanotubes reinforced resin – a new concept: Journal of Structural Integrity and Maintenance: Vol 5, No 2
Stiffening offshore composite wind-blades bonding joints by carbon nanotubes reinforced resin – a new concept: Journal of Structural Integrity and Maintenance: Vol 5, No 2:
Offshore wind-blades with excessive lengths (>100 m) are critical parts because of monolithic bonding that is holding the two halves, which may lead to sudden separation of edges while wind-turbine is in service. Offshore wind generation maintenance teams are targeting zero-maintenance. As a matter of fact, in the event of initiating mechanical damage, top and bottom skins of a wind blade should hold together as long as possible to allow enough time for maintenance to take place......
Y. El Assami, M. Drissi Habti & V. Raman (2020) Stiffening offshore composite wind-blades bonding joints by carbon nanotubes reinforced resin – a new concept,Journal of Structural Integrity and Maintenance,5:2, 87-103, DOI: 10.1080/24705314.2020.1729519
Offshore wind-blades with excessive lengths (>100 m) are critical parts because of monolithic bonding that is holding the two halves, which may lead to sudden separation of edges while wind-turbine is in service. Offshore wind generation maintenance teams are targeting zero-maintenance. As a matter of fact, in the event of initiating mechanical damage, top and bottom skins of a wind blade should hold together as long as possible to allow enough time for maintenance to take place......
Y. El Assami, M. Drissi Habti & V. Raman (2020) Stiffening offshore composite wind-blades bonding joints by carbon nanotubes reinforced resin – a new concept,Journal of Structural Integrity and Maintenance,5:2, 87-103, DOI: 10.1080/24705314.2020.1729519
PERFORMANCE EVALUATION OF A 1kW VARIABLE PITCH-STRAIGHT BLADE VERTICAL AXIS WIND TURBINE | Journal of Energy Resources Technology | ASME Digital Collection
PERFORMANCE EVALUATION OF A 1kW VARIABLE PITCH-STRAIGHT BLADE VERTICAL AXIS WIND TURBINE | Journal of Energy Resources Technology | ASME Digital Collection
This research work represents a study of the design, analysis and experimental study of a 1kW Variable Pitch-Straight Blade Vertical Axis Wind Turbine using Natural Fiber Reinforced Composite. Wind turbine which is an emerging technology is of great interest for researchers nowadays. The Vertical Axis Wind Turbine (VAWT) was chosen for this study because of its numerous advantages over Horizontal Axis Wind Turbine (HAWT). A new concept of Variable Pitch was implemented by the introduction of a pitching mechanism associated to the turbine blades which helps the blade to maximize the generation of torque and power. For this purpose the straight blade H-Rotor design was chosen. The analytical calculations were performed for variable pitch and the fixed pitch blade followed by the CAD modelling of the rotor exhibiting the variable pitching mechanism. CFD analysis of the blade at the azimuth position of 0 to 360 degrees was performed and the CFD results were imported into static structural module of ANSYS for the FE analysis of the blade. The blade was 3D-printed at a reduced scale and tested in a wind tunnel for aerodynamic properties including lift, drag and aerodynamic forces. A comparison was done between the analytical, software and experimental values. Furthermore, basalt fiber which is a natural fiber was used as the material for the turbine blade and analysis was performed to obtain high strength to weight ratio of the composite material. The structure was analyzed under the damage tolerance study to determine, for how long the structure can bear damage. The experimental results showed a good agreement with the analytical and numerical values. The introduction of the variable pitching mechanism resulted in an increase in the cumulative torque as compared to the fixed pitching mechanism which in turn enhanced the resulting power.
This research work represents a study of the design, analysis and experimental study of a 1kW Variable Pitch-Straight Blade Vertical Axis Wind Turbine using Natural Fiber Reinforced Composite. Wind turbine which is an emerging technology is of great interest for researchers nowadays. The Vertical Axis Wind Turbine (VAWT) was chosen for this study because of its numerous advantages over Horizontal Axis Wind Turbine (HAWT). A new concept of Variable Pitch was implemented by the introduction of a pitching mechanism associated to the turbine blades which helps the blade to maximize the generation of torque and power. For this purpose the straight blade H-Rotor design was chosen. The analytical calculations were performed for variable pitch and the fixed pitch blade followed by the CAD modelling of the rotor exhibiting the variable pitching mechanism. CFD analysis of the blade at the azimuth position of 0 to 360 degrees was performed and the CFD results were imported into static structural module of ANSYS for the FE analysis of the blade. The blade was 3D-printed at a reduced scale and tested in a wind tunnel for aerodynamic properties including lift, drag and aerodynamic forces. A comparison was done between the analytical, software and experimental values. Furthermore, basalt fiber which is a natural fiber was used as the material for the turbine blade and analysis was performed to obtain high strength to weight ratio of the composite material. The structure was analyzed under the damage tolerance study to determine, for how long the structure can bear damage. The experimental results showed a good agreement with the analytical and numerical values. The introduction of the variable pitching mechanism resulted in an increase in the cumulative torque as compared to the fixed pitching mechanism which in turn enhanced the resulting power.
A particle swarm optimization–support vector machine hybrid system with acoustic emission on damage degree judgment of carbon fiber reinforced polymer cables - Jie Xu, Xuan Liu, Qinghua Han, Weixin Wang,
A particle swarm optimization–support vector machine hybrid system with acoustic emission on damage degree judgment of carbon fiber reinforced polymer cables - Jie Xu, Xuan Liu, Qinghua Han, Weixin Wang,
The feasibility of machine learning in damage degree judgment of carbon fiber reinforced polymer cables was first verified by the improved b-value method and wavelet packet spectrum analysis. Then, a hybrid system with support vector machine classification and particle swarm optimization algorithms was proposed to realize the prediction. The b-value calculated with all acoustic emission events has better performance when noise cannot be avoided. The 1/b-value has almost the same trend with acoustic emission signal cumulative energy, which can meet the preliminarily needs of health monitoring. The particle swarm optimization clustering algorithm works by using nine characteristic parameters of acoustic emission signals. It demonstrates that the characteristic parameters of acoustic emission signals are closely related to the failure mode of the carbon fiber reinforced polymer cable. This indicates their correspondence to the cable’s damage degree and their ability to work as training data for machine learning. With particle swarm optimization, the trained support vector machine can reach at least 77% accuracy of a single acoustic emission signal when predicting the corresponding current damage degree. In addition, using the voting mechanism can promote the performance of support vector machine. This demonstrates the practicability of applying acoustic emission combined with machine learning as a damage degree judgment method for carbon fiber reinforced polymer cables.
The feasibility of machine learning in damage degree judgment of carbon fiber reinforced polymer cables was first verified by the improved b-value method and wavelet packet spectrum analysis. Then, a hybrid system with support vector machine classification and particle swarm optimization algorithms was proposed to realize the prediction. The b-value calculated with all acoustic emission events has better performance when noise cannot be avoided. The 1/b-value has almost the same trend with acoustic emission signal cumulative energy, which can meet the preliminarily needs of health monitoring. The particle swarm optimization clustering algorithm works by using nine characteristic parameters of acoustic emission signals. It demonstrates that the characteristic parameters of acoustic emission signals are closely related to the failure mode of the carbon fiber reinforced polymer cable. This indicates their correspondence to the cable’s damage degree and their ability to work as training data for machine learning. With particle swarm optimization, the trained support vector machine can reach at least 77% accuracy of a single acoustic emission signal when predicting the corresponding current damage degree. In addition, using the voting mechanism can promote the performance of support vector machine. This demonstrates the practicability of applying acoustic emission combined with machine learning as a damage degree judgment method for carbon fiber reinforced polymer cables.
J. Compos. Sci. | Free Full-Text | Strain State Detection in Composite Structures: Review and New Challenges
J. Compos. Sci. | Free Full-Text | Strain State Detection in Composite Structures: Review and New Challenges
Developing an advanced monitoring system for strain measurements on structural components represents a significant task, both in relation to testing of in-service parameters and early identification of structural problems. This paper aims to provide a state-of-the-art review on strain detection techniques in composite structures. The review represented a good opportunity for direct comparison of different novel strain measurement techniques. Fibers Bragg grating (FBG) was discussed as well as non-contact techniques together with semiconductor strain gauges (SGs), specifically infrared (IR) thermography and the digital image correlation (DIC) applied in order to detect strain and failure growth during the tests. The challenges of the research community are finally discussed by opening the current scenario to new objectives and industrial applications.
Developing an advanced monitoring system for strain measurements on structural components represents a significant task, both in relation to testing of in-service parameters and early identification of structural problems. This paper aims to provide a state-of-the-art review on strain detection techniques in composite structures. The review represented a good opportunity for direct comparison of different novel strain measurement techniques. Fibers Bragg grating (FBG) was discussed as well as non-contact techniques together with semiconductor strain gauges (SGs), specifically infrared (IR) thermography and the digital image correlation (DIC) applied in order to detect strain and failure growth during the tests. The challenges of the research community are finally discussed by opening the current scenario to new objectives and industrial applications.
Investigation into features of fracture toughness of a transparent E-glass fiber reinforced polyester composites at extreme temperatures - ScienceDirect
Investigation into features of fracture toughness of a transparent E-glass fiber reinforced polyester composites at extreme temperatures - ScienceDirect
In recent years, several investigators have made efforts to satisfy industrial and transportation demands with respect to high mechanical properties. Moreover, the transparent composites are needed for automotive and aircraft applications. Thus, developing more efficient and advanced transparent composite techniques has recently got more attention but seldom studied in harsh conditions. The main goal of the present study is to investigate the impact of exposing a transparent polyester composite to different temperatures ranging from high to very low (60, room temperature, 0, -30, -60, and -80 °C) and 50% humidity. ...
In recent years, several investigators have made efforts to satisfy industrial and transportation demands with respect to high mechanical properties. Moreover, the transparent composites are needed for automotive and aircraft applications. Thus, developing more efficient and advanced transparent composite techniques has recently got more attention but seldom studied in harsh conditions. The main goal of the present study is to investigate the impact of exposing a transparent polyester composite to different temperatures ranging from high to very low (60, room temperature, 0, -30, -60, and -80 °C) and 50% humidity. ...
Probabilistic Design of Offshore Wind Turbine Support Structures: Applications of Reliability Methods in Design and Analysis - Danish National Research Database
Probabilistic Design of Offshore Wind Turbine Support Structures: Applications of Reliability Methods in Design and Analysis - Danish National Research Database
There is a growing interest in applications of probabilistic methods in design of offshore wind turbines. As opposed to the classical, deterministic design approach, the probabilistic design approach has the advantage of being able to account for site-specific information, experimental test results and availability of better models. This often leads to more cost-effective design solutions. This Ph.D. thesis explores the applications of probabilistic methods in design and analysis of offshore wind turbine support structures. Some fundamental aspects and considerations are presented, including global sensitivity analysis of numerical load models, structural reliability analysis under fatigue and extreme loads, and reliability-based calibration of fatigue partial safety factors. This work provides valuable insights to researchers and engineers specializing on the fields of support structure design, reliability analysis and risk assessment.
There is a growing interest in applications of probabilistic methods in design of offshore wind turbines. As opposed to the classical, deterministic design approach, the probabilistic design approach has the advantage of being able to account for site-specific information, experimental test results and availability of better models. This often leads to more cost-effective design solutions. This Ph.D. thesis explores the applications of probabilistic methods in design and analysis of offshore wind turbine support structures. Some fundamental aspects and considerations are presented, including global sensitivity analysis of numerical load models, structural reliability analysis under fatigue and extreme loads, and reliability-based calibration of fatigue partial safety factors. This work provides valuable insights to researchers and engineers specializing on the fields of support structure design, reliability analysis and risk assessment.
Spinning finite element analysis of longitudinally stiffened horizontal axis wind turbine blade for fatigue life enhancement - ScienceDirect
Spinning finite element analysis of longitudinally stiffened horizontal axis wind turbine blade for fatigue life enhancement - ScienceDirect
In this study, a proof-of-concept is presented for extending the fatigue life of modern multi-megawatt wind turbine blades. For this purpose, spinning finite element model of the blade is investigated which has longitudinal stiffener (i.e. a tendon along its length) made of shape memory alloy. The material behaviour of the tendon is characterized by Liang and Rogers constitutive model in combination with thermodynamic principles...
In this study, a proof-of-concept is presented for extending the fatigue life of modern multi-megawatt wind turbine blades. For this purpose, spinning finite element model of the blade is investigated which has longitudinal stiffener (i.e. a tendon along its length) made of shape memory alloy. The material behaviour of the tendon is characterized by Liang and Rogers constitutive model in combination with thermodynamic principles...
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