Finite element modeling of dielectric elastomer actuators for space applications

A special actuator device with passive sensing capability based on dielectric elastomer was studied and specialized to be used in space applications. The work illustrates the research project modeling procedure adopted to simulate the mechanical behavior of this material based on a finite element theory approach. The Mooney-Rivlin’s hyperelastic and Maxwell’s electrostatic models provide the theoretical basis to describe its electro-mechanic behavior. The validation of the procedure is performed through a numerical-experimental correlation between the response of a prototype of actuator developed by the Risø Danish research center and the 3D finite element model simulations. An investigation concerning a possible application in the space environment of dielectric elastomer actuators (DEA) is also presented

Detection of low-velocity impact-induced delaminations in composite laminates using Auto-Regressive models

In this paper, the detection of delaminations in carbon-fiber-reinforced-plastic (CFRP) laminate plates induced by low-velocity impacts (LVI) is investigated by means of Auto-Regressive (AR) models obtained from the time histories of the acquired responses of the composite specimens. A couple of piezoelectric patches for actuation and sensing purposes are employed. The proposed structural health monitoring (SHM) routine begins with the selection of the suitable locations of the piezoelectric transducers via the numerical analysis of the curvature mode shapes of the CFRP plates. The normalized data recorded for the undamaged plate configuration are then analyzed to obtain the most suitable AR model using five techniques based on the Akaike Information Criterion (AIC), the Akaike Final Prediction Error (FPE), the Partial Autocorrelation Function (PAF), the Root Mean Squared (RMS) of the AR residuals for different order p, and the Singular Value Decomposition (SVD). Linear Discriminant Analysis (LDA) is then applied on the AR model parameters to enhance the performance of the proposed delamination identification routine. Results show the effectiveness of the developed procedure when a reduced number of sensors is available

Thermomechanical Buckling Analysis of the E&P-FGM Beams Integrated by Nanocomposite Supports Immersed in a Hygrothermal Environment

none4siDue to the widespread use of sandwich structures in many industries and the importance of understanding their mechanical behavior, this paper studies the thermomechanical buckling behavior of sandwich beams with a functionally graded material (FGM) middle layer and two composite external layers. Both composite skins are made of Poly(methyl methacrylate) (PMMA) reinforced by carbon-nano-tubes (CNTs). The properties of the FGM core are predicted through an exponential-law and power-law theory (E&P), whereas an Eshelby-Mori-Tanaka (EMT) formulation is applied to capture the mechanical properties of the external layers. Moreover, different high-order displacement fields are combined with a virtual displacement approach to derive the governing equations of the problem, here solved analytically based on a Navier-type approximation. A parametric study is performed to check for the impact of different core materials and CNT concentrations inside the PMMA on the overall response of beams resting on a Pasternak substrate and subjected to a hygrothermal loading. This means that the sensitivity analysis accounts for different displacement fields, hygrothermal environments, and FGM theories, as a novel aspect of the present work. Our results could be replicated in a computational sense, and could be useful for design purposes in aerospace industries to increase the tolerance of target productions, such as aircraft bodies.Khorasani, Mohammad; Lampani, Luca; Dimitri, Rossana; Tornabene, FrancescoKhorasani, Mohammad; Lampani, Luca; Dimitri, Rossana; Tornabene, Francesc

Finite Element Modeling of Dielectric Elastomer Actuators for Space Applications

A special actuator device with passive sensing capability based on dielectric elastomer was studied and specialized to be used in space applications. The work illustrates the research project modeling procedure adopted to simulate the mechanical behavior of this material based on a finite element theory approach. The Mooney-Rivlin’s hyperelastic and Maxwell’s electrostatic models provide the theoretical basis to describe its electro-mechanic behavior. The validation of the procedure is performed through a numerical-experimental correlation between the response of a prototype of actuator developed by the Risø Danish research center and the 3D finite element model simulations. An investigation concerning a possible application in the space environment of dielectric elastomer actuators (DEA) is also presented.European Space Agenc

Finite element analysis of delamination of a composite component with the cohesive zone model technique

Purpose - The purpose of this paper is to assess a numerical tool to simulate and predict the onset and the propagation of the delaminations in a composite structure. Design/methodology/approach - The approach to the work is done through the cohesive zone model technique applied to the finite element method. Findings - Double cantilever beam, end notched flexure and mixed mode bending tests have been performed and correlated to benchmark cases, in order to validate the procedure. Numerical test campaign on specimens of the skirts with delaminations has been performed to analyze the behaviour under compressive load and the buckling. Originality/value - This tool is applied to the study of the behaviour of some components in carbon/epoxy composite of a space structure in which one or more delaminations are eventually present following impact damage or manufacturing process. The components in particular are the booster's skirts of a small class launcher, subjected to a compressive load

3D Finite Element Analyses of Multilayer Dielectric Elastomer Actuators with Metallic Compliant Electrodes for Space Applications

A special actuator device with passive sensing capability based on dielectric elastomer was studied and specialized to be used in space applications. The work illustrates the research project modeling procedure adopted to simulate the mechanical behavior of this material based on a finite-element theory approach. The Mooney-Rivlin's hyperelastic and Maxwell's electrostatic models provide the theoretical basis to describe its electromechanic behavior. The validation of the procedure is performed through a numerical-experimental correlation between the response of a prototype of actuator developed by the Riso Danish research center and the 3D finite-element model simulations. An investigation concerning a possible application in the space environment of dielectric elastomer actuators is also presented

Elemento strutturale in materiale composito laminato configurato per il monitoraggio del suo stato strutturale

Un componente strutturale, realizzato in materiale composito laminato, è fornito di un dispositivo per il monitoraggio in remoto del suo comportamento strutturale all’interno della sequenza di laminazione. Lo scopo dell’invenzione è quello di sopportare i carichi agenti su di essa come una struttura normale, e di percepire lo stato di sollecitazione e/o deformazione e/o vibrazione e/o temperatura cui è soggetta trasmettendo tale stato ad una stazione di monitoraggio in remoto. Tale capacità è ottenuta attraverso una rete di senso/attuatori piezoelettrici cablati ad una unità di processamento dati. Tale unità è collegata ad una stazione in remoto tramite trasmissione radio per l’invio dei dati acquisiti. Il dispositivo elettronico è alimentato attraverso un circuito di energy harvesting che trasforma le vibrazioni meccaniche in potenza elettrica, permettendo al dispositivo stesso di funzionare senza una sorgente esterna di alimentazione o batterie.A structural component, manufactured in laminated composite material is provided of an embedded sensor device to monitor his structural behaviour and transmit it via wireless radio connection. “ The aim of the invention is both to supporting loads, as a common structure, and to sense the state of stress and/or deformation and/or the dynamic mechanical loading and/or the temperature to which it is subjected “. This capability is achieved by mean of a network of flat sensors, wired to a processing unit. Such unit is linked to a remote control station via wireless radio connection to transmit the acquired data. The electronic equipment is powered by an embedded energy harvesting circuit that transduce the mechanical vibrations in electric power, allowing the device to work without an external power source or a battery

Numerical Simulation of the Behaviour of Inflatable Structures for Space

Lightweight, efficient packaging and large operational size in space are the ideal requirements in gossamer structures and membrane materials. Several kinds of these structures were built over the years as demonstrators of spacecraft subsystems. The difficulty to foresee the response of these components during the deployment and/or inflation phase in space or microgravity environments has increased the efforts to simulate their behaviour. The aim of this work is to presents a collection of analyses performed by finite element approaches on some benchmark cases set up by the European Space Agency. These cases have the purpose of both assessing reliable numerical methods and software packages and providing solutions for some basic engineering problems in this field. The considered cases are listed below and include different phenomena: pressurization and bending deflection of a structure in space in the presence of microgravity environment, deployment analysis of inflated structures, prediction of the wrinkling pattern and the wrinkles amplitude of thin membrane subjected to shear loading along the edges