Offshore Wind Farm Technology | TU Delft Online
Offshore wind energy is a fast growing renewable energy technology that is built upon the expertise of several engineering disciplines. Engineers who work in wind farm design, operation and maintenance must understand the various disciplines involved in order to meet energy production and cost reductions goals. This is equally true of professionals who are new to this field.
31 août 2020
20 août 2020
Failure analysis of GFRP single lap joints tailored with a combination of tough epoxy and hyperelastic adhesives - ScienceDirect
Failure analysis of GFRP single lap joints tailored with a combination of tough epoxy and hyperelastic adhesives - ScienceDirect
Fibre reinforced polymeric composites bonded with epoxy adhesives often fail ungraciously, manifesting fibre-tear failure due to the edge peel stresses. This research work proposes phenol formaldehyde-based hyperelastic adhesive (AF32), as a compliant adhesive for tailoring the single lap joints consisting of GFRP adherends and well-toughened epoxy adhesive (AF3109 and EA9696) joints. The failure strength of the AF3109 and EA9696 adhesive joints is increased by 51.64% and 24.25%, respectively by having 20% volume of compliant adhesive in the bond line. Finite element simulations with Exponential Drucker-Prager (EDP) and Marlow strain energy models are carried out to simulate the experimental load-displacement response. Different failure mechanisms and the influence of adhesive intermingling are revealed by the failure analysis. Finally, a failure mode map for the tailored adhesive joints is proposed in terms of normalised strength ratio and the normalised volume of the compliant adhesive.
Fibre reinforced polymeric composites bonded with epoxy adhesives often fail ungraciously, manifesting fibre-tear failure due to the edge peel stresses. This research work proposes phenol formaldehyde-based hyperelastic adhesive (AF32), as a compliant adhesive for tailoring the single lap joints consisting of GFRP adherends and well-toughened epoxy adhesive (AF3109 and EA9696) joints. The failure strength of the AF3109 and EA9696 adhesive joints is increased by 51.64% and 24.25%, respectively by having 20% volume of compliant adhesive in the bond line. Finite element simulations with Exponential Drucker-Prager (EDP) and Marlow strain energy models are carried out to simulate the experimental load-displacement response. Different failure mechanisms and the influence of adhesive intermingling are revealed by the failure analysis. Finally, a failure mode map for the tailored adhesive joints is proposed in terms of normalised strength ratio and the normalised volume of the compliant adhesive.
19 août 2020
Pedestrianisation of Soho hailed a success as 90% of hospitality businesses reopen | London Evening Standard
Pedestrianisation of Soho hailed a success as 90% of hospitality businesses reopen | London Evening Standard
The pedestrianisation of Soho has been hailed a success, as 90 per cent of the area’s hospitality businesses have reportedly reopened.While at one point much of the area looked at risk of collapse, the campaign to allow restaurants to serve al fresco appears to have offered a lifeline to many.
The pedestrianisation of Soho has been hailed a success, as 90 per cent of the area’s hospitality businesses have reportedly reopened.While at one point much of the area looked at risk of collapse, the campaign to allow restaurants to serve al fresco appears to have offered a lifeline to many.
A review of 3D and 4D printing of natural fibre biocomposites - ScienceDirect
A review of 3D and 4D printing of natural fibre biocomposites - ScienceDirect
To date, the literature has focused on synthetic fibre-reinforced composites, but it has not adequately addressed the unique properties that differentiate natural from synthetic fibres, such as their natural variation in microstructure and composition across species. This review paper proposes a critical overview of the current state of 3D printing of natural fibre-reinforced composites or biocomposites for mechanical purposes, as well as an overview of their role in 4D printing for stimuli-responsive applications. The paper is structured as follows: after the first part recalling the specificities of natural fibres and their associated composites, the two main sections are each divided into two parts presenting an analysis of the available data to provide fundamental understandings and a discussion and outlook for the future.....
To date, the literature has focused on synthetic fibre-reinforced composites, but it has not adequately addressed the unique properties that differentiate natural from synthetic fibres, such as their natural variation in microstructure and composition across species. This review paper proposes a critical overview of the current state of 3D printing of natural fibre-reinforced composites or biocomposites for mechanical purposes, as well as an overview of their role in 4D printing for stimuli-responsive applications. The paper is structured as follows: after the first part recalling the specificities of natural fibres and their associated composites, the two main sections are each divided into two parts presenting an analysis of the available data to provide fundamental understandings and a discussion and outlook for the future.....
14 août 2020
Fibres naturelles de renfort pour matériaux composites : Dossier complet | Techniques de l’Ingénieur
Fibres naturelles de renfort pour matériaux composites : Dossier complet | Techniques de l’Ingénieur
Les industriels s’intéressent de plus en plus au renforcement des polymères par des fibres naturelles pour, généralement, réduire les impacts environnementaux. La sélection de ce type de renfort n’est pas simple, ce terme correspondant à des fibres d’origine végétale, animale ou minérale. Après un classement, cet article aborde les deux premières familles en présentant les ressources disponibles, leurs propriétés et spécificités puis leur usage comme renfort de matériaux composites.
Les industriels s’intéressent de plus en plus au renforcement des polymères par des fibres naturelles pour, généralement, réduire les impacts environnementaux. La sélection de ce type de renfort n’est pas simple, ce terme correspondant à des fibres d’origine végétale, animale ou minérale. Après un classement, cet article aborde les deux premières familles en présentant les ressources disponibles, leurs propriétés et spécificités puis leur usage comme renfort de matériaux composites.
13 août 2020
Effect of fibre waviness on the compressive fatigue behavior of woven carbon/epoxy laminates - ScienceDirect
Effect of fibre waviness on the compressive fatigue behavior of woven carbon/epoxy laminates - ScienceDirect
In the present work, two woven carbon/epoxy laminates with different aerial weight were tested under tension-compression (R = -1) and compression-compression (R = -∞) cyclic loadings. Their performance was evaluated in terms life to final separation and stiffness degradation during the fatigue life. In addition, microscopic observations were carried out at regular intervals during the tests to identify the damage evolution at the micro-scale. The bundle waviness was found to have a large influence on the damage mechanisms and the fatigue life of the laminates both for tension-compression and compression-compression loadings, while the stiffness loss remained small until final failure in all cases.
In the present work, two woven carbon/epoxy laminates with different aerial weight were tested under tension-compression (R = -1) and compression-compression (R = -∞) cyclic loadings. Their performance was evaluated in terms life to final separation and stiffness degradation during the fatigue life. In addition, microscopic observations were carried out at regular intervals during the tests to identify the damage evolution at the micro-scale. The bundle waviness was found to have a large influence on the damage mechanisms and the fatigue life of the laminates both for tension-compression and compression-compression loadings, while the stiffness loss remained small until final failure in all cases.
12 août 2020
Transdisciplinary top-down review of hemp fibre composites: from an advanced product design to crop variety selection – A critical review - ScienceDirect
Transdisciplinary top-down review of hemp fibre composites: from an advanced product design to crop variety selection – A critical review - ScienceDirect
Given the vast amount of available research in the area of natural fibre composites, a significant step forward in the development of next-generation plant fibre-based products would be to devise a framework for rational design. The authors use a top-down approach, starting with an example final product to define the product specifications for high-performance hemp fibre-reinforced composites. Thereafter, all process steps are critically analysed: from textile preform and reinforcement yarn production, to fibre extraction and the agricultural process chain, to the microbiology of field retting, to cultivation and selection of crop variety. The aim of the analysis is to determine how far the current state of knowledge and process technologies are in order to use hemp fibres in high-performance composites. Based on this critical evaluation of the state-of-the-art, it can be stated that hemp will be found in high-performance composites in the short-to-medium term......
Given the vast amount of available research in the area of natural fibre composites, a significant step forward in the development of next-generation plant fibre-based products would be to devise a framework for rational design. The authors use a top-down approach, starting with an example final product to define the product specifications for high-performance hemp fibre-reinforced composites. Thereafter, all process steps are critically analysed: from textile preform and reinforcement yarn production, to fibre extraction and the agricultural process chain, to the microbiology of field retting, to cultivation and selection of crop variety. The aim of the analysis is to determine how far the current state of knowledge and process technologies are in order to use hemp fibres in high-performance composites. Based on this critical evaluation of the state-of-the-art, it can be stated that hemp will be found in high-performance composites in the short-to-medium term......
MULTI SEGMENT WIND TURBINE BLADE JOINT BUSHING - Roller Bearing Company of America, Inc.
MULTI SEGMENT WIND TURBINE BLADE JOINT BUSHING - Roller Bearing Company of America, Inc.
A joint bushing that accommodates the dithering and sliding in multi segment wind turbines. The joint bushing includes a self-lubricating liner that is a composite system incorporating woven Polytetrafluoroethylene fibers intermixed with structural reinforcement fibers in a composite matrix. The composite system provides sufficient life without requiring re-lubrication.
A joint bushing that accommodates the dithering and sliding in multi segment wind turbines. The joint bushing includes a self-lubricating liner that is a composite system incorporating woven Polytetrafluoroethylene fibers intermixed with structural reinforcement fibers in a composite matrix. The composite system provides sufficient life without requiring re-lubrication.
A review of non-destructive testing on wind turbines blades - ScienceDirect
A review of non-destructive testing on wind turbines blades - ScienceDirect
Wind energy, with an exponential growth in the last years, is nowadays one of the most important renewable energy sources. Modern wind turbines are bigger and complex to produce more energy. This industry requires to reduce its operating and maintenance costs and to increase its reliability, safety, maintainability and availability. Condition monitoring systems are beginning to be employed for this purpose. They must be reliable and cost-effective to reduce the long periods of downtimes and high maintenance costs, and to avoid catastrophic scenarios caused by undetected failures. This paper presents a survey about the most important and updated condition monitoring techniques based on non-destructive testing and methods applied to wind turbine blades. In addition, it analyses the future trends and challenges of structural health monitoring systems in wind turbine blades.
Wind energy, with an exponential growth in the last years, is nowadays one of the most important renewable energy sources. Modern wind turbines are bigger and complex to produce more energy. This industry requires to reduce its operating and maintenance costs and to increase its reliability, safety, maintainability and availability. Condition monitoring systems are beginning to be employed for this purpose. They must be reliable and cost-effective to reduce the long periods of downtimes and high maintenance costs, and to avoid catastrophic scenarios caused by undetected failures. This paper presents a survey about the most important and updated condition monitoring techniques based on non-destructive testing and methods applied to wind turbine blades. In addition, it analyses the future trends and challenges of structural health monitoring systems in wind turbine blades.
Self-Healing Composite of Thermoset Polymer and Programmed Super Contraction Fibers - Board of Supervisors of Louisiana State University and Agricultural and Mechanical College
Self-Healing Composite of Thermoset Polymer and Programmed Super Contraction Fibers - Board of Supervisors of Louisiana State University and Agricultural and Mechanical College
A composition comprising thermoset polymer, shape memory polymer to facilitate macro scale damage closure, and a means for molecular scale healing is disclosed; the composition has the ability to resolve structural defects by a bio-mimetic close-then heal process. In use, the shape memory polymer serves to bring surfaces of a structural defect into approximation, whereafter use of the means for molecular scale healing allowed for movement of the healing means into the defect and thus obtain molecular scale healing. The means for molecular scale healing can be a thermoplastic such as fibers, particles or spheres which are used by heating to a level at or above the thermoplastic's melting point, then cooling of the composition below the melting temperature of the thermoplastic. Compositions of the invention have the ability to not only close macroscopic defects, but also to do so repeatedly even if another wound/damage occurs in a previously healed/repaired area.
A composition comprising thermoset polymer, shape memory polymer to facilitate macro scale damage closure, and a means for molecular scale healing is disclosed; the composition has the ability to resolve structural defects by a bio-mimetic close-then heal process. In use, the shape memory polymer serves to bring surfaces of a structural defect into approximation, whereafter use of the means for molecular scale healing allowed for movement of the healing means into the defect and thus obtain molecular scale healing. The means for molecular scale healing can be a thermoplastic such as fibers, particles or spheres which are used by heating to a level at or above the thermoplastic's melting point, then cooling of the composition below the melting temperature of the thermoplastic. Compositions of the invention have the ability to not only close macroscopic defects, but also to do so repeatedly even if another wound/damage occurs in a previously healed/repaired area.
Joining Behavior of Jute/Sisal Fibers Based Epoxy Laminates Using Different Joint Configurations: Journal of Natural Fibers: Vol 0, No 0
Joining Behavior of Jute/Sisal Fibers Based Epoxy Laminates Using Different Joint Configurations: Journal of Natural Fibers: Vol 0, No 0
The natural fiber-based polymeric composites are being used extensively in various engineering applications, especially in the non-structural parts and components. Although, a large number of primary processing techniques, such as hand-layup and compression molding are available for fabrication of parts, still the secondary processing in terms of joining and machining is inevitable. The joining of composite parts becomes necessary in case of complicated and intricate product designs. Adhesive joining is one of the most commonly used processes for polymer-based composite materials. It is a cheap, easy, and smooth bonding process and does not necessitate the drilling of holes for the purpose of mechanical fastening. In the present experimental investigation, the joint strength of woven fiber mat (sisal, jute, and hybrid) reinforced epoxy composites has been investigated using different joint configurations, namely, single lap, double-strap butt, and scarf joint. The effect of adhesives has also been explored by joining composites with two types of epoxy resins and corresponding hardener. It was observed that the hybrid composites recorded better joining performance for both types of adhesives. Moreover, the Field Emission Scanning Electron Microscopy (FE-SEM) has been used to understand the failure mechanisms during tensile testing of adhesively bonded natural fiber-reinforced composite laminates. The three-dimensional assembly models of adherend specimens were created using the SOLIDWORK V.16 modeling software. ANSYS-V.18.2 WORKBENCH was employed for the analysis of the joint performance. The maximum shear stress and the total deformation results were determined. The finite element analysis (FEA) results were compared with experimental findings and were found to be in good agreement.
The natural fiber-based polymeric composites are being used extensively in various engineering applications, especially in the non-structural parts and components. Although, a large number of primary processing techniques, such as hand-layup and compression molding are available for fabrication of parts, still the secondary processing in terms of joining and machining is inevitable. The joining of composite parts becomes necessary in case of complicated and intricate product designs. Adhesive joining is one of the most commonly used processes for polymer-based composite materials. It is a cheap, easy, and smooth bonding process and does not necessitate the drilling of holes for the purpose of mechanical fastening. In the present experimental investigation, the joint strength of woven fiber mat (sisal, jute, and hybrid) reinforced epoxy composites has been investigated using different joint configurations, namely, single lap, double-strap butt, and scarf joint. The effect of adhesives has also been explored by joining composites with two types of epoxy resins and corresponding hardener. It was observed that the hybrid composites recorded better joining performance for both types of adhesives. Moreover, the Field Emission Scanning Electron Microscopy (FE-SEM) has been used to understand the failure mechanisms during tensile testing of adhesively bonded natural fiber-reinforced composite laminates. The three-dimensional assembly models of adherend specimens were created using the SOLIDWORK V.16 modeling software. ANSYS-V.18.2 WORKBENCH was employed for the analysis of the joint performance. The maximum shear stress and the total deformation results were determined. The finite element analysis (FEA) results were compared with experimental findings and were found to be in good agreement.
Joining Behavior of Jute/Sisal Fibers Based Epoxy Laminates Using Different Joint Configurations: Journal of Natural Fibers: Vol 0, No 0
Joining Behavior of Jute/Sisal Fibers Based Epoxy Laminates Using Different Joint Configurations: Journal of Natural Fibers: Vol 0, No 0
The natural fiber-based polymeric composites are being used extensively in various engineering applications, especially in the non-structural parts and components. Although, a large number of primary processing techniques, such as hand-layup and compression molding are available for fabrication of parts, still the secondary processing in terms of joining and machining is inevitable. The joining of composite parts becomes necessary in case of complicated and intricate product designs. Adhesive joining is one of the most commonly used processes for polymer-based composite materials. It is a cheap, easy, and smooth bonding process and does not necessitate the drilling of holes for the purpose of mechanical fastening. In the present experimental investigation, the joint strength of woven fiber mat (sisal, jute, and hybrid) reinforced epoxy composites has been investigated using different joint configurations, namely, single lap, double-strap butt, and scarf joint. The effect of adhesives has also been explored by joining composites with two types of epoxy resins and corresponding hardener. It was observed that the hybrid composites recorded better joining performance for both types of adhesives. Moreover, the Field Emission Scanning Electron Microscopy (FE-SEM) has been used to understand the failure mechanisms during tensile testing of adhesively bonded natural fiber-reinforced composite laminates. The three-dimensional assembly models of adherend specimens were created using the SOLIDWORK V.16 modeling software. ANSYS-V.18.2 WORKBENCH was employed for the analysis of the joint performance. The maximum shear stress and the total deformation results were determined. The finite element analysis (FEA) results were compared with experimental findings and were found to be in good agreement.
The natural fiber-based polymeric composites are being used extensively in various engineering applications, especially in the non-structural parts and components. Although, a large number of primary processing techniques, such as hand-layup and compression molding are available for fabrication of parts, still the secondary processing in terms of joining and machining is inevitable. The joining of composite parts becomes necessary in case of complicated and intricate product designs. Adhesive joining is one of the most commonly used processes for polymer-based composite materials. It is a cheap, easy, and smooth bonding process and does not necessitate the drilling of holes for the purpose of mechanical fastening. In the present experimental investigation, the joint strength of woven fiber mat (sisal, jute, and hybrid) reinforced epoxy composites has been investigated using different joint configurations, namely, single lap, double-strap butt, and scarf joint. The effect of adhesives has also been explored by joining composites with two types of epoxy resins and corresponding hardener. It was observed that the hybrid composites recorded better joining performance for both types of adhesives. Moreover, the Field Emission Scanning Electron Microscopy (FE-SEM) has been used to understand the failure mechanisms during tensile testing of adhesively bonded natural fiber-reinforced composite laminates. The three-dimensional assembly models of adherend specimens were created using the SOLIDWORK V.16 modeling software. ANSYS-V.18.2 WORKBENCH was employed for the analysis of the joint performance. The maximum shear stress and the total deformation results were determined. The finite element analysis (FEA) results were compared with experimental findings and were found to be in good agreement.
Performance comparison of resin-infused thermoplastic and thermoset 3D fabric composites under impact loading - ScienceDirect
Performance comparison of resin-infused thermoplastic and thermoset 3D fabric composites under impact loading - ScienceDirect
In this paper, the impact performance of a novel resin-infused acrylic thermoplastic matrix-based 3D glass fabric composite (3D-FRC) has been evaluated and compared with thermoset based 3D-FRC under single as well as recurring strike low velocity impact (LVI) events. The single impact tests revealed that the thermoplastic-based 3D-FRC exhibits up to 45% reduced damage area and can have up to 20% higher impact load-bearing capacity (peak force). The damage mode characterization showed that damage transition energy required for micro to macro damage transition is 27% higher, and back face damage extension is up to 3 times less for thermoplastic-based 3D-FRC.
In this paper, the impact performance of a novel resin-infused acrylic thermoplastic matrix-based 3D glass fabric composite (3D-FRC) has been evaluated and compared with thermoset based 3D-FRC under single as well as recurring strike low velocity impact (LVI) events. The single impact tests revealed that the thermoplastic-based 3D-FRC exhibits up to 45% reduced damage area and can have up to 20% higher impact load-bearing capacity (peak force). The damage mode characterization showed that damage transition energy required for micro to macro damage transition is 27% higher, and back face damage extension is up to 3 times less for thermoplastic-based 3D-FRC.
11 août 2020
21 juillet 2020
On fatigue stress-cycle curves of carbon, glass and hybrid carbon/glass-reinforced fibre metal laminates - ScienceDirect
On fatigue stress-cycle curves of carbon, glass and hybrid carbon/glass-reinforced fibre metal laminates - ScienceDirect
In this paper, theoretical predictions of static and fatigue strength were performed and validated experimentally of conventional and carbon/glass fibres reinforced hybrid fibre metal laminates (FMLs). It was found, that the hybrid glass/carbon FMLs are featured by lower static but higher fatigue strength than glass reinforces laminates currently using in aircraft. The potential for fatigue resistance was proposed as a new comparable parameter describing global fatigue response of the laminates. It was theoretically predicted and experimentally confirmed that the fatigue degradation of laminates is governed by either composite failure or aluminium fatigue, depending on the loading magnitude.
In this paper, theoretical predictions of static and fatigue strength were performed and validated experimentally of conventional and carbon/glass fibres reinforced hybrid fibre metal laminates (FMLs). It was found, that the hybrid glass/carbon FMLs are featured by lower static but higher fatigue strength than glass reinforces laminates currently using in aircraft. The potential for fatigue resistance was proposed as a new comparable parameter describing global fatigue response of the laminates. It was theoretically predicted and experimentally confirmed that the fatigue degradation of laminates is governed by either composite failure or aluminium fatigue, depending on the loading magnitude.
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