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CONTENTS
Volume 2, Number 3, July 2015
 

Abstract
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Key Words
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Address
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Abstract
Frame structures have been traditionally represented as an assembling of components, these last described within the beam theory framework. In the case of frames involving complex components in which classical beam theory could fail, 3D descriptions seem the only valid route for performing accurate enough analyses. In this work we propose a framework for frame structure analyses that proceeds by assembling the condensed parametric rigidity matrices associated with the elementary beams composing the beams involved in the frame structure. This approach allows a macroscopic analysis in which only the condensed degrees of freedom at the elementary beams interfaces are considered, while fine 3D parametric descriptions are retained for local analyses.

Key Words
PGD; parametric solutions; model reduction; frame structures; shape optimization

Address
Felipe Bordeu, Chady Ghnatios, Adrien Leygue and Francisco Chinesta: GeM UMR CNRS-Centrale Nantes, 1 rue de la Noe, F-44300 Nantes, France
Daniel Boulze, Beatrice Carles, Damien Sireude: AEROLIA, 13 rue Marie-Louise Dissard, BP 73216, 31027 Toulouse, Cedex 3, France

Abstract
The mechanical characterization of composite materials is nowadays a major interest due to their increasing use in the aeronautic industry. The design of most of these materials is based on their stiffness, which is mainly obtained by means of tensile tests with strain gauge measurement. For thin laminated composites, this classical method requires adequate samples with specific orientation and does not provide all the independent elastic constants. Regarding ultrasonic characterization, especially immersion technique, only one specimen is needed and the entire determination of the stiffness tensor is possible. This paper presents a study of different methods to determine the mechanical properties of transversely isotropic carbon fibre composite materials (gauge and correlation strain measurement during tensile tests, ultrasonic immersion technique). Results are compared to ISO standards and manufacturer data to evaluate the accuracy of these techniques.

Key Words
carbon fibre composite; elastic constants; immersion ultrasonic characterization; tensile test; stiffness tensor

Address
Victor Munoz, Helene Welemane, Moussa Karama: Universite de Toulouse, INP-ENIT, LGP, 47 avenue d\'Azereix, 65016 Tarbes, France
Marianne Perrin, Marie-Laetitia Pastor, Arthur Cantarel: Universite de Toulouse, IUT, ICA, 1 rue Lautreamont, BP 1624, 65016 Tarbes, France

Abstract
Carbon nanotube strain sensors, or so called \"fuzzy fiber\" sensors have not yet been studied sufficiently. These sensors are composed of a bundle of fiberglass fibers coated with CNT through a thermal chemical vapor deposition process. The characteristics of these fuzzy fiber sensors differ from a conventional nanocomposite in that the CNTs are anchored to a substrate fiber and the CNTs have a preferential orientation due to this bonding to the substrate fiber. A numerical model was constructed to predict the strain response of a composite with embedded fuzzy fiber sensors in order to compare result with the experimental results obtained in an earlier study. A comparison of the numerical and experimental responses was conducted based on this work. The longitudinal sensor output from the model matches nearly perfectly with the experimental results. The transverse and off-axis tests follow the correct trends; however the magnitude of the output does not match well with the experimental data. An explanation of the disparity is proposed based on microstructural interactions between individual nanotubes within the sensor.

Key Words
carbon nanotubes; fuzzy fiber; strain sensing; Structural Health Monitoring (SHM); nanocomposite

Address
M. Boehle, P. Pianca, K. Lafdi: University of Dayton Research Institute, 300 College Park, Dayton, OH 45469, USA
F. Chinesta: Ecole Centrale of Nantes, 1 rue de la Noe, BP 92101, 44321 Nantes cedex 3, France

Abstract
Theoretical and numerical assessments of approximate evaluations and simplified analyses of piezoelectric structures transverse shear modal effective electromechanical coupling coefficient (EMCC) are presented. Therefore, the latter is first introduced theoretically and its approximate evaluations are reviewed; then, three-dimensional (3D) and simplified two-dimensional (2D) plane-strain (PStrain) and plane-stress (PStress) piezoelectric constitutive behaviors of electroded shear piezoceramic patches are derived and corresponding expected short-circuit (SC) and open-circuit (OC) frequencies and resulting EMCC are discussed; next, using a piezoceramic shear sandwich beam cantilever typical benchmark, a 3D finite element (FE) assessment of different evaluation techniques of the shear modal effective EMCC is conducted, including the equipotential (EP) constraints effect; finally, 2D PStrain and PStress FE modal analyses under SC and OC electric conditions, are conducted and corresponding results (SC/OC frequencies and resulting effective EMCC) are compared to 3D ones. It is found that: (i) physical EP constraints reduce drastically the shear modal effective EMCC; (ii) PStress and PStrain results depend strongly on the filling foam stiffness, rendering inadequate the use of popular equivalent single layer models for the transverse shear-mode sandwich configuration; (iii) in contrary to results of piezoelectric shunted damping and energy harvesting popular single-degree-of-freedom-based models, transverse shear modal effective EMCC values are very small in particular for the first mode which is the common target of these applications.

Key Words
piezoceramic materials; shear response; modal effective electromechanical coupling coefficient; approximate evaluation; plane-strain; plane-stress; short-circuit; open-circuit; free-vibration; finite element

Address
Ayech Benjeddou: Institut Supérieur de Mécanique de Paris, 3 rue Fernand Hainaut, 93400 Saint Ouen, France

Abstract
A design methodology is presented to develop the hingeless control surfaces for MAV using adhesively bonded Macro Fiber Composite (MFC) actuators. These actuators have got the capability to deflect the trailing edge surfaces of the wing to attain the required maneuverability, besides achieving the set aerodynamic trim condition. A scheme involving design, analysis, fabrication and testing procedure has been adopted to realize the trailing edge morphing mechanism. The stiffness distribution of the composite MAV wing is tailored such that the induced deflection by piezoelectric actuation is approximately optimized. Through ground testing, the proposed concept has been demonstrated on a typical MAV structure. Electromechanical analysis is performed to evaluate the actuator performance and subsequently aeroelastic and 2D CFD analyses are carried out to see the functional requirements of wing trailing edge surfaces to behave as elevons. Efforts have been made to obtain the performance comparison of conventional control surfaces (elevons) with morphing wing trailing edge surfaces. A significant improvement in lift to drag ratio is noticed with morphed wing configuration in comparison to conventional wing. Further, it has been shown that the morphed wing trailing edge surfaces can be deployed as elevons for aerodynamic trim applications.

Key Words
micro air vehicle (MAV); macro fiber composite (MFC); morphing; aeroelasticity; computational fluid dynamics (CFD)

Address
D. Dwarakanathan, R. Ramkumar, S. Raja and P. Siva Subba Rao: Dynamics and Adaptive Structures, Structural Technologies Division, CSIR-National Aerospace Laboratories, Bangalore, India

Abstract
This study aimed to observe the effect of a novel concept (referred to as the flap extension) implemented on the leading edge of the flap of a three element high lift device. The high lift device, consisting of a flap, main element and slat is designed around an Airbus research profile for sufficient take off and landing performance of a large commercial aircraft. The concept is realised on the profile and numerically optimised to achieve an optimum geometry. Two different optimisation approaches based on Genetic Algorithm optimisations are used: a zero order approach which makes simplifying assumptions to achieve an optimised solution: as well as a direct approach which employs an optimisation in ANSYS DesignXplorer using RANS calculations. Both methods converge to different optimised solutions due to simplifying assumptions. The solution to the zero order optimisation showed a decreased stall angle and decreased maximum lift coefficient against angle of attack due to early stall onset at the flap. The DesignXplorer optimised solution matched that of the baseline solution very closely. The concept was seen to increase lift locally at the flap for both optimisation methods.

Key Words
aerodynamic design; high lift; single slotted flap; optimization; aeroacoustics; CFD

Address
Jason D.M. Botha: School of Mechanical Industrial and Aeronautical Engineering, University of the Witwatersrand, Private Bag 3, Wits 2050, South Africa
Laurent Dala: CSIR, DPSS: Aeronautics Systems, PO Box 395, Pretoria 0001, South Africa
S. Schaber: Airbus Operations GmbH, AIRBUS-ALLEE 1, D-28199 Bremen, Germany

Abstract
This paper focuses on the design, fabrication, testing and analysis of a novel load-bearing element with energy dissipation capability. A single element comprises two von-Mises trusses (VMTs), which are sandwiched between two plates and connected to dashpots that stroke as the VMTs cycle between stable equilibrium states. The elements can be assembled in-plane to form a large plate-like structure or stacked with different properties in each layer for improved load-adaptability. Also introduced in the elements are pre-loaded springs (PLSs) that provide high initial stiffness and allow the element to carry a static load even when the VMTs cannot under harmonic disturbance input. Simulations of the system behavior using the Simscape environment show good overall correlation with test data. Good energy dissipation capability is observed over a frequency range from 0.1 Hz to 2 Hz. The test and simulation results show that a two layer prototype, having one soft VMT layer and one stiff VMT layer, can provide good energy dissipation over a decade of variation in harmonic load amplitude, while retaining the ability to carry static load due to the PLSs. The paper discusses how system design parameter changes affect the static load capability and the hysteresis behavior.

Key Words
load adaptability; damping; energy dissipation; von-Mises truss; snap-through

Address
Michael E. Pontecorvo, Silvestro Barbarino, Farhan S. Gandhi: Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
Scott Bland, Robert Snyder, Jay Kudva: NextGen Aeronautics Inc., Torrance, CA, 90505, USA
Edward V. White: The Boeing Company, Berkeley, MO, 63134, USA


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