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CONTENTS
Volume 9, Number 3, May 2022
 


Abstract
By the present paper, both experimental and analytical models have been proposed to study the vibration behavior of partially bio-sourced sandwich panel with orthogonally stiffened core. For a variable mass fraction of Alfa fibers from 5% to 15%, impregnated in a Medapoxy STR resin, this panel were manufactured by molding the orthogonally stiffened core then attached it with both skins. Using simply supported boundary conditions, a free vibration test was carried out using an impact hammer for predicting the natural frequencies, the mode shapes and the damping coefficient versus the fibers content. In addition, an analytical model based on the Higher order Shear Deformation Theory (HSDT) was developed to predict natural frequencies and the mode shapes according to Navier's solution. From the experimental test, we have found that the frequency increases with the increase in the mass fraction of the fibers until 10%. Beyond this fraction, the frequencies give relatively lower values. For the analytical model, variation of the natural frequencies increased considerably with side-to-thickness ratio (a/H) and equivalent thickness of the core to thickness of the face (hs/h). We concluded that, the vibration behavior was significantly influenced by geometrical and mechanical properties of the partially bio-sourced sandwich panel.

Key Words
equivalent stiffness; orthogonally stiffeners; sandwich panel; short Alfa fibers; vibration behavior

Address
Aicha Boussoufi, Lahouaria Errouane, Zouaoui Sereir: Laboratoire Structures des Composites et MatériauxInnovants, Department of Marine Engineering, University of Science and Technology of Oran, BP 1505 El M'naouer USTO, Oran, Algeria
José V. Antunes, Vincent Debut: Applied Dynamics Laboratory, Instituto Technològico e Nuclear, ITN/ADL, Estrada Nacional 10, 2686 Sacavem Codex, Portugal

Abstract
The increasing interest in CubeSat platforms ant their capability of enlarging the frontier of possible missions impose technology improvements. Miniaturized electrical propulsion (EP) systems enable new mission for multi-unit CubeSats (6U+). While electric propulsion systems have achieved important level of knowledge at equipment level, the investigation of the mutual impact between EP system and CubeSat technology at system level can provide a decisive improvement for both the technologies. The interaction between CubeSat and EP system should be assessed in terms of electromagnetic emissions (both radiated and conducted), thermal gradients, high electrical power management, surface chemical deposition, and quick and reliable data exchanges. This paper shows how a versatile CubeSat Test Platform (CTP), together with standardized procedures and specialized facilities enable the acquisition fundamental and unprecedented information. Measurements can be taken both by specific ground support equipment placed inside the vacuum facility and by dedicated sensors and subsystems installed on the CTP, providing a completely new set of data never obtained before. CTP is constituted of a 6U primary structure hosting the EP system, representative CubeSat avionics and batteries. For the first test campaign, CTP hosts the ambipolar plasma propulsion system, called Regulus and developed by T4I. After the integration and the functional test in laboratory environment, CTP + Regulus performed a Test campaign in relevant environment in the vacuum chamber at CISAS, University of Padua. This paper is focused on the test campaign description and the main results achieved at different power levels for different duration of the firings.

Key Words
CubeSat Test Platform; environmental tests campaign; miniaturized ambipolar plasma thruster; small satellites

Address
Fabrizio Stesina, Sabrina Corpino: Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, Torino, Italy
Eduard Bosch Borras, Josè Gonzalez Del Amo: European Space Agency (ESA), ESTEC, Kepleerlan 1, Noordwijk, The Netherlands
Daniele Pavarin: Technology for Innovation (T4I), Via Altinate 125, 35121 Padova (PD), Italy; Università di Padova (CISAS), Via Venezia 59/4. 35129 Padova (PD), Italy
Nicolas Bellomo, Fabio Trezzolani: Technology for Innovation (T4I), Via Altinate 125, 35121 Padova (PD), Italy

Abstract
This paper proposes a novel time-domain homogenization model combining the viscoelastic constitutive law with Eshelby's inclusion theory-based micromechanics model to predict the mechanical behavior of the particle reinforced composite material. The proposed model is intuitive and straightforward capable of predicting composites' viscoelastic behavior in the time domain. The isotropization technique for non-uniform stress-strain fields and incremental Mori-Tanaka schemes for high volume fraction are adopted in this study. Effects of the imperfectly bonded interphase layer on the viscoelastic behavior on the dynamic mechanical behavior are also investigated. The proposed model is verified by the direct numerical simulation and DMA (dynamic mechanical analysis) experimental results. The proposed model is useful for multiscale analysis of viscoelastic composite materials, and it can also be extended to predict the nonlinear viscoelastic response of composite materials.

Key Words
Eshelby inclusion theory; homogenization; micromechanics; particulate composite; viscoelastic material

Address
Hangil You, Hyoung Jun Lim: Department of Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul, 08826, South Korea
Gun Jin Yun: Department of Aerospace Engineering, Seoul National University, Gwanak-gu, Seoul, 08826, South Korea; Institute of Advanced Aerospace Technology, Seoul National University, 08826, Seoul, South Korea

Abstract
Broad writing on the examination of sandwich structures mirrors the significance of incorporating thermal loadings during their investigation stage. In the current work, an endeavor has been made to concentrate on sandwich FGM beams' bending behaving under thermal loadings utilizing shear deformation theory. Temperature-dependent material properties are used during the analysis. The formulation includes the transverse displacement field, which helps better predict the behavior of thick FGM beams. Three-different thermal profiles across the thickness of the beam are assumed during the analysis. The study has been carried out on both symmetric and unsymmetric sandwich FGM beams. It has been observed that the bending behavior of sandwich FGM beams is impacted by the temperature profile to which it is subjected. Power-law exponent and thickness of core also affect the behavior of the beam.

Key Words
exponential; finite element; sandwich FGM beam; sigmoidal; thermal bending

Address
Aman Garg: Department of Civil and Environmental Engineering, The NorthCap University, Gurugram, Haryana, 122017, India
Mohamed-Ouejdi Belarbi: Laboratoire de Génie Energétique et Matériaux, LGEM, Faculté de la Science et de lo Technologie, Université de Biskra, B.P. 145, R.P. 07000, Biskra, Algeria
Li Li: State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science
and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Abdelouahed Tounsi: YFL (Yonsei Frontier Lab), Yonsei University, Seoul, Korea; Department of Civil and Environmental Engineering, King Fahd University of Petroleum &Minerals, 31261 Dhahran, Eastern Province, Saudi Arabia;
Material and Hydrology Laboratory, Faculty of Technology, Civil Engineering Department, University of Sidi Bel Abbes, 22000 Sidi Bel Abbes, Algeria

Abstract
The time-varying structural reliability of an aeroelastic launch vehicle subjected to stochastic parameters is investigated. The launch vehicle structure is under the combined action of several stochastic loads that include aerodynamics, thrust as well as internal combustion pressure. The launch vehicle's main body structural flexibility is modeled via the normal mode shapes of a free-free Euler beam, where the aerodynamic loadings on the vehicle are due to force on each incremental section of the vehicle. The rigid and elastic coupled nonlinear equations of motion are derived following the Lagrangian approach that results in a complete aeroelastic simulation for the prediction of the instantaneous launch vehicle rigid-body motion as well as the body elastic deformations. Reliability analysis has been performed based on two distinct limit state functions, defined as the maximum launch vehicle tip elastic deformation and also the maximum allowable stress occurring along the launch vehicle total length. In this fashion, the timedependent reliability problem can be converted into an equivalent time-invariant reliability problem. Subsequently, the first-order reliability method, as well as the Monte Carlo simulation schemes, are employed to determine and verify the aeroelastic launch vehicle dynamic failure probability for a given flight time.

Key Words
dynamic modeling; extreme response; flexible; FORM; launch vehicle; reliability

Address
Seid H. Pourtakdoust and A.H. Khodabaksh: Center for Research and Development in Space Science and Technology, Sharif University of Technology, Tehran, 145888 9694, Iran


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