Silvain Michel | Swiss Federal Institute of Technology (ETH) (original) (raw)

Papers by Silvain Michel

Research paper thumbnail of Very high cycle fatigue tests of quenched and self-tempered steel reinforcement bars

Materials and Structures, 2015

Investigations on the fatigue strength of steel reinforcement bars (rebars) mainly involves fatig... more Investigations on the fatigue strength of steel reinforcement bars (rebars) mainly involves fatigue tests with hot rolled (HR) and cold worked (CW) steels. However, in the last few decades, HR and CW rebars were replaced by quenched and selftempered (QST) rebars with hardened surface layer. There still remains a lack of research on fatigue strength of QST rebars especially in the very high cycle domain i.e., number of stress cycles surpassing 5 million. This study is part of a further detailed investigation on the fatigue behaviour of HR, CW and QST rebars in the very high cycle domain. It aims to investigate the fatigue performance of QST rebars axially tested at number of stress cycles in the range of 10 6 -10 8 . A preliminary study of the gripping method is followed by fatigue test results including nondestructive inspection of the rebar surface and fractographic analyses. The rebar surface is examined with liquid penetrant to reveal fatigue crack location and size in specific frequency interval monitored during the tests. Fractured surface analyses are performed by scanning electron microscopy to detect the location from where fatigue cracks initiate. Cross sectional area reduction resulting from fatigue crack propagation is also determined. Fractographic investigations are compared with the fractured surfaces of HR, CW and QST rebars from the literature.

Research paper thumbnail of Enabling large scale capacitive sensing for dielectric elastomers

Electroactive Polymer Actuators and Devices (EAPAD) 2014, 2014

ABSTRACT Hand motion is one of our most expressive abilities. By measuring our interactions with ... more ABSTRACT Hand motion is one of our most expressive abilities. By measuring our interactions with everyday objects, we can create smarter artificial intelligence that can learn and adapt from our behaviours and patterns. One way to achieve this is to apply wearable dielectric elastomer strain sensors directly onto the hand. Applications such as this require fast, efficient and scalable sensing electronics. Most capacitive sensing methods use an analogue sensing signal and a backend processor to calculate capacitance. This not only reduces scalability and speed of feedback but also increases the complexity of the sensing circuitry. A capacitive sensing method that uses a DC sensing signal and continuous tracking of charge is presented. The method is simple and efficient, allowing large numbers of dielectric elastomer sensors to be measured simulatenously.

Research paper thumbnail of Characterization of dielectric elastomer actuators based on a hyperelastic film model

Sensors and Actuators A: Physical, 2007

The focus of this paper is on the energy characterization of dielectric elastomer (DE) actuators ... more The focus of this paper is on the energy characterization of dielectric elastomer (DE) actuators under quasi-static activation cycles. To this end, a simple model covering the basic mechanical effects of hyperelastic dielectric elastomer films was introduced and fitted to the experimental behavior of the widely used dielectric film VHB 4910 in a uniaxial tensile test. The film model was then applied to planar DE actuators by introducing the electromechanical coupling of the electrodes to the film. The evaluation of this system permitted the characterization of the inner force equilibrium states of planar DE actuators under activation with either constant charge or constant voltage. In a second step, a quasi-static activation cycle of an idealized DE strip actuator with uniaxial prestrain was simulated. The configuration was evaluated regarding the characteristics of the specific work output per cycle as well as the overall electromechanical efficiency for various activation voltage levels and different prestrain levels.

Research paper thumbnail of Non-intuitive fracture pattern of a failed crane-hanger: A fracture mechanics-based explanation

Engineering Failure Analysis, 2015

ABSTRACT

Research paper thumbnail of Propulsion Unit for Lighter-Than-Air Aircraft

Research paper thumbnail of <title>Large planar dielectric elastomer actuators for fish-like propulsion of an airship</title>

Electroactive Polymer Actuators and Devices (EAPAD) 2010, 2010

One of the great advantages of dielectric elastomers (DE) is their scalability. Large planar DE a... more One of the great advantages of dielectric elastomers (DE) is their scalability. Large planar DE are quite unique in the world of actuators. An interesting application of such actuators is the activation of inflatable structures. As research platform a model airship of 8 m in length was constructed that can move its body and tail fin in a fish-like manner. Unlike the propulsion with propellers, the fish-like movement is silent and the airflow around the airship is not disturbed. The bending actuation of the helium-filled hull is realized with planar two-layered DE of 1.6 m 2 on either side. The tail fin is moved by four-layer planar DE of 0.3 m 2 on either side. A design for actuators of such dimensions was developed and the actuators were characterized in terms of their performance.

Research paper thumbnail of Feasibility studies for a bionic propulsion system of a blimp based on Dielectric Elastomers

Proceedings of Spie the International Society For Optical Engineering, May 1, 2008

After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight contro... more After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight control, a novel biologically inspired propulsion system based on DE is envisaged. The basic idea is to mimic a fish body motion by deforming a) the envelope of the rear lifting body and b) flapping an aft-tail. In both cases, planar DEs are used, either fully integrated in the envelope (for a) and/or arranged as an active hinge (for b). In a theoretical study the specifications of a steady-state horizontal indoor flight of 1 m/s were defined. In an experimental work the concept of an active hull element, which consists of a balloon hull material and several layers of DE actuators was verified. The specific boundary conditions of a slightly pressurized elliptical membrane body were simulated in a biaxial test. It could be shown, that the necessary active strains to reach the specified body deformations were reached. In a second study an aero-elastic fin was designed. Based on fluid-dynamic similarity principles the size, shape and stiffness of the fin were determined and tested in preliminary flight test with a three meter long blimp. The main goal of 1 m/s flight velocity could be shown.

Research paper thumbnail of Scaling of planar dielectric elastomer actuators in an agonist-antagonist configuration

Sensors and Actuators A: Physical, 2010

One of the great advantages of dielectric elastomers (DE) is their scalability. This study invest... more One of the great advantages of dielectric elastomers (DE) is their scalability. This study investigates the influence of size on their performance and the applicability of theory and established models on large-scale actuators. The testing is based on an active hinge configuration made with planar dielectric elastomer actuators as described by Lochmatter in 2007 [16]. The actuators are scaled to

Research paper thumbnail of Standards for dielectric elastomer transducers

Smart Materials and Structures, 2015

ABSTRACT

Research paper thumbnail of Dielectric Elastomer Actuators for A Portable Force Feedback Device

This paper focuses on the development of novel actuators for a portable force feedback glove for,... more This paper focuses on the development of novel actuators for a portable force feedback glove for, but not limited to, the simulation of open surgeries. A conceptual design of a chain-like actuator based on electroactive polymers is introduced. One actuator element of this chain was built in order to explore and optimize the actuator manufacturing process. Actuators manufactured with this stable process were characterized through isometric and isotonic measurements. The results show that dielectric elastomer actuators are promising for a portable force feedback device.

Research paper thumbnail of <title>Electromechanical model for static and dynamic activation of elementary dielectric elastomer actuators</title>

Smart Structures and Materials 2006: Electroactive Polymer Actuators and Devices (EAPAD), 2006

In this work the electromechanical performance of planar, single-layered dielectric elastomer (DE... more In this work the electromechanical performance of planar, single-layered dielectric elastomer (DE) actuators was investigated. The mechanical power density and the overall electromechanical efficiency of DE stripe actuators under continuous activation cycles were examined. The viscoelastic behavior of the dielectric film was modeled with a threedimensionally coupled spring-damper framework. This film model was fitted to the mechanical behavior of the acrylic film VHB 4910 (3M) evaluated in a combination of a uniaxial loading test with holding time and subsequent unloading. In addition the quasielastic film model was derived in order to evaluate the quasistatic behavior of DE actuators under activation. For the simulation of DE actuators the boundary conditions of the film model were accordingly adapted. By embedding the actuator into an appropriate electrical circuit electrodynamic effects were incorporated as well. The quasielastic model of a planar DE actuator with free boundary conditions predicted a stable deformation state for activation with constant charge. For activation with constant electrical voltage, however, the model showed a stable and an instable equilibrium state. For activation voltages beyond a critical voltage the film collapses in thickness direction due to the electrostatic forces (Maxwell stresses). A biaxially prestrained stripe actuator was described with the viscoelastic film model. The stripe actuator was cyclically activated and cyclically elongated with a phase shift (displacement-controlled). A qualitative parameter study showed that the overall electromechanical efficiency as well as the specific power density of such DE actuators strongly depends on the electrical activation and the external mechanical loading.

Research paper thumbnail of Biomimetics in airship design

Many attempts have been made to mimic the movement of a fish in water in order to find novel solu... more Many attempts have been made to mimic the movement of a fish in water in order to find novel solutions in autonomous underwater vehicles (AUV) . Conventional airships are driven by propellers and steered by stabilizers with rudders or with thrust vector control. Such propulsion and steering systems are efficient only in a small range of operation. The goal of our project is to mimic the fish-like movement with an airship body in air. In a theoretical study we have shown that a 6m long airship in air is similar to the trout in water. Therefore we want to build a geometrically similar body which mimics the body motion of a trout in steady state swimming. The activation is realized using Dielectric Elastomers (DE), a promising class of Electroactive Polymers (EAP). The principles of biomimetics in structural design and propulsion are discussed in this paper. The similarity of the optimized solutions found by the evolution for animals living in water and an optimized design of an airship will be shown. In a next step, the design of an indoor-flying airship propelled by a fish-like motion is evaluated. Various development tests, including wind tunnel testing and flight trials were performed and the gained results will be presented. First computational fluiddynamic simulations performed have shown similar vortex flow fields. In addition, the average forces could be measured accurately in wind tunnel tests and will be used to dimensioning the activation of the fin appropriately. From these results a conclusion shall be drawn, how far biomimetics can be used successfully in the design of future airship. Fin Ray Effect®

Research paper thumbnail of Body segment of an active airship based on dielectric elastomers

Many attempts have been made to mimic the movement of a fish in water, for their propulsion is ve... more Many attempts have been made to mimic the movement of a fish in water, for their propulsion is very efficient and can be optimized for various parameters such as e.g. speed, acceleration or manoeuvrability. Conventional airships are driven by propellers, which is efficient, but only in a small range of application. The goal is therefore to copy the fish-like movement in air. Dielectric electro-active polymer actuators (EAP) are used to bend the airship body because of their light weight, because of the large deformations they can achieve and because a large-scale planar application is possible. The manufacturing and characterization of one bending airship body segment with planar dielectric elastomer actuators is described in this paper. In a conceptual study, several designs for the combination of EAP actuator with airship hull were evaluated qualitatively and quantitatively. From these results a conclusion shall be drawn, which design to use in the final biomimetic airship.

Research paper thumbnail of Sensing frequency design for capacitance feedback of dielectric elastomers

Sensors and Actuators A: Physical, 2015

ABSTRACT Dielectric elastomers, also known as artificial muscles have produced many biomimetic ro... more ABSTRACT Dielectric elastomers, also known as artificial muscles have produced many biomimetic robots. One advantage is their ability to provide feedback through capacitance. However when the sensing frequency is too high, the measured capacitance can underestimate the true value. In this paper, the measured capacitance of dielectric elastomer stacked and rolled configurations were shown to reduce with increasing sensing frequency. A transmission line electrical model linked this to the result of high interconnect and sheet resistances of the electrodes. A design methodology to help determine the working limits of sensing frequency is presented.

Research paper thumbnail of Feasability Studies for a Bionic Blimp with a Fish-Like Propulsion Systems

7th AIAA ATIO Conf, 2nd CEIAT Int'l Conf on Innov and Integr in Aero Sciences,17th LTA Systems Tech Conf; followed by 2nd TEOS Forum, 2007

Research paper thumbnail of <title>Electroactive polymers as a novel actuator technology for lighter-than-air vehicles</title>

Electroactive Polymer Actuators and Devices (EAPAD) 2007, 2007

In this paper the worldwide first EAP actuated blimp will be presented. It consists of a slightly... more In this paper the worldwide first EAP actuated blimp will be presented. It consists of a slightly pressurized Helium filled body of a biologically inspired form with Dielectric Elastomer (DE) actuators driving a classical cross tail with two vertical and horizontal rudders for flight control. Two versions of actuators will be discussed: The first version consisted of "spring-roll" type of cylindrical actuators placed together with the electrical supply and control unit in the pay load gondola. The second version consisted of a configuration, where the actuators are placed between the control surfaces and the rudders. This novel type of EAP actuator named "active hinge" was developed and characterized first in the laboratory and afterwards optimized for minimum weight and finally integrated in the blimp structure. In the design phase a numerical simulation tool for the prediction of the DE actuators was developed based on a material model calibrated with the test results from cylindrical actuators. The electrical supply and control system was developed and optimized for minimum of weight. Special attention was paid to the electromagnetic systems compatibility of the high voltage electrical supply system of the DE actuators and the radio flight control system. The design and production of this 3.5 meter long Lighter-than-Air vehicle was collaboration between Empa Duebendorf Switzerland and the Technical University of Berlin. The first version of this EAP blimp first flew at an RC airship regatta hold on 24 th of June 2006 in Dresden Germany, while the second version had his maiden flight on 8 th of January 2007 in Duebendorf Switzerland. In both cases satisfactory flight control performances were demonstrated.

Research paper thumbnail of Exposure assessment of a high energy tensile test with large carbon fiber reinforced polymer cables

Journal of occupational and environmental hygiene, Jan 19, 2015

This study investigated the particle and fiber release from two carbon fiber reinforced polymer c... more This study investigated the particle and fiber release from two carbon fiber reinforced polymer cables that underwent high energy tensile tests until rupture. The failing event was the source of a large amount of dust whereof a part was suspected to be containing possibly respirable fibers that could cause adverse health effects. The released fibers were suspected to migrate through small openings to the experiment control room and also to an adjacent machine hall where workers were active.To investigate the fiber release and exposure risk of the affected workers, the generated particles were measured with aerosol devices to obtain the particle size and the particle concentrations. Furthermore particles were collected on filter samples to investigate the particle shape and the fiber concentration.Three situations were monitored for the control room and the machine hall: the background concentrations, the impact of the cable failure, and the venting of the exposed rooms afterward. Th...

Research paper thumbnail of <title>Feasibility studies for a bionic propulsion system of a blimp based on dielectric elastomers</title>

Electroactive Polymer Actuators and Devices (EAPAD) 2008, 2008

After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight contro... more After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight control, a novel biologically inspired propulsion system based on DE is envisaged. The basic idea is to mimic a fish body motion by deforming a) the envelope of the rear lifting body and b) flapping an aft-tail. In both cases, planar DEs are used, either fully integrated in the envelope (for a) and/or arranged as an active hinge (for b). In a theoretical study the specifications of a steady-state horizontal indoor flight of 1 m/s were defined. In an experimental work the concept of an active hull element, which consists of a balloon hull material and several layers of DE actuators was verified. The specific boundary conditions of a slightly pressurized elliptical membrane body were simulated in a biaxial test. It could be shown, that the necessary active strains to reach the specified body deformations were reached. In a second study an aero-elastic fin was designed. Based on fluid-dynamic similarity principles the size, shape and stiffness of the fin were determined and tested in preliminary flight test with a three meter long blimp. The main goal of 1 m/s flight velocity could be shown.

Research paper thumbnail of <title>Study on core free rolled actuator based on soft dielectric EAP</title>

Electroactive Polymer Actuators and Devices (EAPAD) 2008, 2008

The rolled actuator represents a design where the pre-stretched EAP film is wrapped many times ar... more The rolled actuator represents a design where the pre-stretched EAP film is wrapped many times around a spring core in order to form a multilayer actuator system with unidirectional actuation. The freestanding rolled configuration enables the use of the DE film for muscle like linear actuators with a broad application potential. The stress state of the prestrained acrylic film in the rolled configuration and the required stiff core can cause several serious problems concerning lifetime, size and efficiency of the actuator.

Research paper thumbnail of Performance evaluation of cutting-edge dielectric elastomers for large-scale actuator applications

Smart Materials and Structures, 2011

Page 1. Performance evaluation of cutting-edge dielectric elastomers for large-scale actuator app... more Page 1. Performance evaluation of cutting-edge dielectric elastomers for large-scale actuator applications This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2011 Smart Mater. Struct. 20 075003 ...

Research paper thumbnail of Very high cycle fatigue tests of quenched and self-tempered steel reinforcement bars

Materials and Structures, 2015

Investigations on the fatigue strength of steel reinforcement bars (rebars) mainly involves fatig... more Investigations on the fatigue strength of steel reinforcement bars (rebars) mainly involves fatigue tests with hot rolled (HR) and cold worked (CW) steels. However, in the last few decades, HR and CW rebars were replaced by quenched and selftempered (QST) rebars with hardened surface layer. There still remains a lack of research on fatigue strength of QST rebars especially in the very high cycle domain i.e., number of stress cycles surpassing 5 million. This study is part of a further detailed investigation on the fatigue behaviour of HR, CW and QST rebars in the very high cycle domain. It aims to investigate the fatigue performance of QST rebars axially tested at number of stress cycles in the range of 10 6 -10 8 . A preliminary study of the gripping method is followed by fatigue test results including nondestructive inspection of the rebar surface and fractographic analyses. The rebar surface is examined with liquid penetrant to reveal fatigue crack location and size in specific frequency interval monitored during the tests. Fractured surface analyses are performed by scanning electron microscopy to detect the location from where fatigue cracks initiate. Cross sectional area reduction resulting from fatigue crack propagation is also determined. Fractographic investigations are compared with the fractured surfaces of HR, CW and QST rebars from the literature.

Research paper thumbnail of Enabling large scale capacitive sensing for dielectric elastomers

Electroactive Polymer Actuators and Devices (EAPAD) 2014, 2014

ABSTRACT Hand motion is one of our most expressive abilities. By measuring our interactions with ... more ABSTRACT Hand motion is one of our most expressive abilities. By measuring our interactions with everyday objects, we can create smarter artificial intelligence that can learn and adapt from our behaviours and patterns. One way to achieve this is to apply wearable dielectric elastomer strain sensors directly onto the hand. Applications such as this require fast, efficient and scalable sensing electronics. Most capacitive sensing methods use an analogue sensing signal and a backend processor to calculate capacitance. This not only reduces scalability and speed of feedback but also increases the complexity of the sensing circuitry. A capacitive sensing method that uses a DC sensing signal and continuous tracking of charge is presented. The method is simple and efficient, allowing large numbers of dielectric elastomer sensors to be measured simulatenously.

Research paper thumbnail of Characterization of dielectric elastomer actuators based on a hyperelastic film model

Sensors and Actuators A: Physical, 2007

The focus of this paper is on the energy characterization of dielectric elastomer (DE) actuators ... more The focus of this paper is on the energy characterization of dielectric elastomer (DE) actuators under quasi-static activation cycles. To this end, a simple model covering the basic mechanical effects of hyperelastic dielectric elastomer films was introduced and fitted to the experimental behavior of the widely used dielectric film VHB 4910 in a uniaxial tensile test. The film model was then applied to planar DE actuators by introducing the electromechanical coupling of the electrodes to the film. The evaluation of this system permitted the characterization of the inner force equilibrium states of planar DE actuators under activation with either constant charge or constant voltage. In a second step, a quasi-static activation cycle of an idealized DE strip actuator with uniaxial prestrain was simulated. The configuration was evaluated regarding the characteristics of the specific work output per cycle as well as the overall electromechanical efficiency for various activation voltage levels and different prestrain levels.

Research paper thumbnail of Non-intuitive fracture pattern of a failed crane-hanger: A fracture mechanics-based explanation

Engineering Failure Analysis, 2015

ABSTRACT

Research paper thumbnail of Propulsion Unit for Lighter-Than-Air Aircraft

Research paper thumbnail of <title>Large planar dielectric elastomer actuators for fish-like propulsion of an airship</title>

Electroactive Polymer Actuators and Devices (EAPAD) 2010, 2010

One of the great advantages of dielectric elastomers (DE) is their scalability. Large planar DE a... more One of the great advantages of dielectric elastomers (DE) is their scalability. Large planar DE are quite unique in the world of actuators. An interesting application of such actuators is the activation of inflatable structures. As research platform a model airship of 8 m in length was constructed that can move its body and tail fin in a fish-like manner. Unlike the propulsion with propellers, the fish-like movement is silent and the airflow around the airship is not disturbed. The bending actuation of the helium-filled hull is realized with planar two-layered DE of 1.6 m 2 on either side. The tail fin is moved by four-layer planar DE of 0.3 m 2 on either side. A design for actuators of such dimensions was developed and the actuators were characterized in terms of their performance.

Research paper thumbnail of Feasibility studies for a bionic propulsion system of a blimp based on Dielectric Elastomers

Proceedings of Spie the International Society For Optical Engineering, May 1, 2008

After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight contro... more After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight control, a novel biologically inspired propulsion system based on DE is envisaged. The basic idea is to mimic a fish body motion by deforming a) the envelope of the rear lifting body and b) flapping an aft-tail. In both cases, planar DEs are used, either fully integrated in the envelope (for a) and/or arranged as an active hinge (for b). In a theoretical study the specifications of a steady-state horizontal indoor flight of 1 m/s were defined. In an experimental work the concept of an active hull element, which consists of a balloon hull material and several layers of DE actuators was verified. The specific boundary conditions of a slightly pressurized elliptical membrane body were simulated in a biaxial test. It could be shown, that the necessary active strains to reach the specified body deformations were reached. In a second study an aero-elastic fin was designed. Based on fluid-dynamic similarity principles the size, shape and stiffness of the fin were determined and tested in preliminary flight test with a three meter long blimp. The main goal of 1 m/s flight velocity could be shown.

Research paper thumbnail of Scaling of planar dielectric elastomer actuators in an agonist-antagonist configuration

Sensors and Actuators A: Physical, 2010

One of the great advantages of dielectric elastomers (DE) is their scalability. This study invest... more One of the great advantages of dielectric elastomers (DE) is their scalability. This study investigates the influence of size on their performance and the applicability of theory and established models on large-scale actuators. The testing is based on an active hinge configuration made with planar dielectric elastomer actuators as described by Lochmatter in 2007 [16]. The actuators are scaled to

Research paper thumbnail of Standards for dielectric elastomer transducers

Smart Materials and Structures, 2015

ABSTRACT

Research paper thumbnail of Dielectric Elastomer Actuators for A Portable Force Feedback Device

This paper focuses on the development of novel actuators for a portable force feedback glove for,... more This paper focuses on the development of novel actuators for a portable force feedback glove for, but not limited to, the simulation of open surgeries. A conceptual design of a chain-like actuator based on electroactive polymers is introduced. One actuator element of this chain was built in order to explore and optimize the actuator manufacturing process. Actuators manufactured with this stable process were characterized through isometric and isotonic measurements. The results show that dielectric elastomer actuators are promising for a portable force feedback device.

Research paper thumbnail of <title>Electromechanical model for static and dynamic activation of elementary dielectric elastomer actuators</title>

Smart Structures and Materials 2006: Electroactive Polymer Actuators and Devices (EAPAD), 2006

In this work the electromechanical performance of planar, single-layered dielectric elastomer (DE... more In this work the electromechanical performance of planar, single-layered dielectric elastomer (DE) actuators was investigated. The mechanical power density and the overall electromechanical efficiency of DE stripe actuators under continuous activation cycles were examined. The viscoelastic behavior of the dielectric film was modeled with a threedimensionally coupled spring-damper framework. This film model was fitted to the mechanical behavior of the acrylic film VHB 4910 (3M) evaluated in a combination of a uniaxial loading test with holding time and subsequent unloading. In addition the quasielastic film model was derived in order to evaluate the quasistatic behavior of DE actuators under activation. For the simulation of DE actuators the boundary conditions of the film model were accordingly adapted. By embedding the actuator into an appropriate electrical circuit electrodynamic effects were incorporated as well. The quasielastic model of a planar DE actuator with free boundary conditions predicted a stable deformation state for activation with constant charge. For activation with constant electrical voltage, however, the model showed a stable and an instable equilibrium state. For activation voltages beyond a critical voltage the film collapses in thickness direction due to the electrostatic forces (Maxwell stresses). A biaxially prestrained stripe actuator was described with the viscoelastic film model. The stripe actuator was cyclically activated and cyclically elongated with a phase shift (displacement-controlled). A qualitative parameter study showed that the overall electromechanical efficiency as well as the specific power density of such DE actuators strongly depends on the electrical activation and the external mechanical loading.

Research paper thumbnail of Biomimetics in airship design

Many attempts have been made to mimic the movement of a fish in water in order to find novel solu... more Many attempts have been made to mimic the movement of a fish in water in order to find novel solutions in autonomous underwater vehicles (AUV) . Conventional airships are driven by propellers and steered by stabilizers with rudders or with thrust vector control. Such propulsion and steering systems are efficient only in a small range of operation. The goal of our project is to mimic the fish-like movement with an airship body in air. In a theoretical study we have shown that a 6m long airship in air is similar to the trout in water. Therefore we want to build a geometrically similar body which mimics the body motion of a trout in steady state swimming. The activation is realized using Dielectric Elastomers (DE), a promising class of Electroactive Polymers (EAP). The principles of biomimetics in structural design and propulsion are discussed in this paper. The similarity of the optimized solutions found by the evolution for animals living in water and an optimized design of an airship will be shown. In a next step, the design of an indoor-flying airship propelled by a fish-like motion is evaluated. Various development tests, including wind tunnel testing and flight trials were performed and the gained results will be presented. First computational fluiddynamic simulations performed have shown similar vortex flow fields. In addition, the average forces could be measured accurately in wind tunnel tests and will be used to dimensioning the activation of the fin appropriately. From these results a conclusion shall be drawn, how far biomimetics can be used successfully in the design of future airship. Fin Ray Effect®

Research paper thumbnail of Body segment of an active airship based on dielectric elastomers

Many attempts have been made to mimic the movement of a fish in water, for their propulsion is ve... more Many attempts have been made to mimic the movement of a fish in water, for their propulsion is very efficient and can be optimized for various parameters such as e.g. speed, acceleration or manoeuvrability. Conventional airships are driven by propellers, which is efficient, but only in a small range of application. The goal is therefore to copy the fish-like movement in air. Dielectric electro-active polymer actuators (EAP) are used to bend the airship body because of their light weight, because of the large deformations they can achieve and because a large-scale planar application is possible. The manufacturing and characterization of one bending airship body segment with planar dielectric elastomer actuators is described in this paper. In a conceptual study, several designs for the combination of EAP actuator with airship hull were evaluated qualitatively and quantitatively. From these results a conclusion shall be drawn, which design to use in the final biomimetic airship.

Research paper thumbnail of Sensing frequency design for capacitance feedback of dielectric elastomers

Sensors and Actuators A: Physical, 2015

ABSTRACT Dielectric elastomers, also known as artificial muscles have produced many biomimetic ro... more ABSTRACT Dielectric elastomers, also known as artificial muscles have produced many biomimetic robots. One advantage is their ability to provide feedback through capacitance. However when the sensing frequency is too high, the measured capacitance can underestimate the true value. In this paper, the measured capacitance of dielectric elastomer stacked and rolled configurations were shown to reduce with increasing sensing frequency. A transmission line electrical model linked this to the result of high interconnect and sheet resistances of the electrodes. A design methodology to help determine the working limits of sensing frequency is presented.

Research paper thumbnail of Feasability Studies for a Bionic Blimp with a Fish-Like Propulsion Systems

7th AIAA ATIO Conf, 2nd CEIAT Int'l Conf on Innov and Integr in Aero Sciences,17th LTA Systems Tech Conf; followed by 2nd TEOS Forum, 2007

Research paper thumbnail of <title>Electroactive polymers as a novel actuator technology for lighter-than-air vehicles</title>

Electroactive Polymer Actuators and Devices (EAPAD) 2007, 2007

In this paper the worldwide first EAP actuated blimp will be presented. It consists of a slightly... more In this paper the worldwide first EAP actuated blimp will be presented. It consists of a slightly pressurized Helium filled body of a biologically inspired form with Dielectric Elastomer (DE) actuators driving a classical cross tail with two vertical and horizontal rudders for flight control. Two versions of actuators will be discussed: The first version consisted of "spring-roll" type of cylindrical actuators placed together with the electrical supply and control unit in the pay load gondola. The second version consisted of a configuration, where the actuators are placed between the control surfaces and the rudders. This novel type of EAP actuator named "active hinge" was developed and characterized first in the laboratory and afterwards optimized for minimum weight and finally integrated in the blimp structure. In the design phase a numerical simulation tool for the prediction of the DE actuators was developed based on a material model calibrated with the test results from cylindrical actuators. The electrical supply and control system was developed and optimized for minimum of weight. Special attention was paid to the electromagnetic systems compatibility of the high voltage electrical supply system of the DE actuators and the radio flight control system. The design and production of this 3.5 meter long Lighter-than-Air vehicle was collaboration between Empa Duebendorf Switzerland and the Technical University of Berlin. The first version of this EAP blimp first flew at an RC airship regatta hold on 24 th of June 2006 in Dresden Germany, while the second version had his maiden flight on 8 th of January 2007 in Duebendorf Switzerland. In both cases satisfactory flight control performances were demonstrated.

Research paper thumbnail of Exposure assessment of a high energy tensile test with large carbon fiber reinforced polymer cables

Journal of occupational and environmental hygiene, Jan 19, 2015

This study investigated the particle and fiber release from two carbon fiber reinforced polymer c... more This study investigated the particle and fiber release from two carbon fiber reinforced polymer cables that underwent high energy tensile tests until rupture. The failing event was the source of a large amount of dust whereof a part was suspected to be containing possibly respirable fibers that could cause adverse health effects. The released fibers were suspected to migrate through small openings to the experiment control room and also to an adjacent machine hall where workers were active.To investigate the fiber release and exposure risk of the affected workers, the generated particles were measured with aerosol devices to obtain the particle size and the particle concentrations. Furthermore particles were collected on filter samples to investigate the particle shape and the fiber concentration.Three situations were monitored for the control room and the machine hall: the background concentrations, the impact of the cable failure, and the venting of the exposed rooms afterward. Th...

Research paper thumbnail of <title>Feasibility studies for a bionic propulsion system of a blimp based on dielectric elastomers</title>

Electroactive Polymer Actuators and Devices (EAPAD) 2008, 2008

After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight contro... more After having successfully integrated Dielectric Elastomers (DE) in a cross tail for flight control, a novel biologically inspired propulsion system based on DE is envisaged. The basic idea is to mimic a fish body motion by deforming a) the envelope of the rear lifting body and b) flapping an aft-tail. In both cases, planar DEs are used, either fully integrated in the envelope (for a) and/or arranged as an active hinge (for b). In a theoretical study the specifications of a steady-state horizontal indoor flight of 1 m/s were defined. In an experimental work the concept of an active hull element, which consists of a balloon hull material and several layers of DE actuators was verified. The specific boundary conditions of a slightly pressurized elliptical membrane body were simulated in a biaxial test. It could be shown, that the necessary active strains to reach the specified body deformations were reached. In a second study an aero-elastic fin was designed. Based on fluid-dynamic similarity principles the size, shape and stiffness of the fin were determined and tested in preliminary flight test with a three meter long blimp. The main goal of 1 m/s flight velocity could be shown.

Research paper thumbnail of <title>Study on core free rolled actuator based on soft dielectric EAP</title>

Electroactive Polymer Actuators and Devices (EAPAD) 2008, 2008

The rolled actuator represents a design where the pre-stretched EAP film is wrapped many times ar... more The rolled actuator represents a design where the pre-stretched EAP film is wrapped many times around a spring core in order to form a multilayer actuator system with unidirectional actuation. The freestanding rolled configuration enables the use of the DE film for muscle like linear actuators with a broad application potential. The stress state of the prestrained acrylic film in the rolled configuration and the required stiff core can cause several serious problems concerning lifetime, size and efficiency of the actuator.

Research paper thumbnail of Performance evaluation of cutting-edge dielectric elastomers for large-scale actuator applications

Smart Materials and Structures, 2011

Page 1. Performance evaluation of cutting-edge dielectric elastomers for large-scale actuator app... more Page 1. Performance evaluation of cutting-edge dielectric elastomers for large-scale actuator applications This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2011 Smart Mater. Struct. 20 075003 ...