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CONTENTS
Volume 7, Number 6, November 2020
 

Abstract
This paper is focused on the characterization of the thermomechanical properties of semicrystalline poly-ether-ether-ketone (PEKK) and of carbon fiber reinforced thermoplastic based laminated composites (C/PEKK) below and above the glass transition temperature (T_g). Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and tensile tests are carried out on both pure PEKK polymer and [(±45)2, +45]s C/PEKK composite samples, showing a significant similarity in behavior. The employment of a simple micromechanical model confirms that the mechanical and physical behavior of the polymer and that of the matrix in the composite are similar.

Key Words
PEKK; carbon fiber reinforced thermoplastic matrix

Address
Giuseppe Pedoto, Olga Smerdova, Jean-Claude Grandidier and Marco Gigliotti: Department of Physics and Mechanics of Materials, PPRIME Institute, CNRS, ISAE-ENSMA, University of Poitiers, France

Alain Vinet: Airbus S.A.S. 2, Building D42 18 Marius Terce 31025 Toulouse France


Abstract
Nonlinear state estimation is a desirable and required technique for many situations in engineering (e.g., aircraft/spacecraft tracking, space situational awareness, collision warning, radar tracking, etc.). Due to high standards on performance in these applications, in the last few decades, there was an increasing demand for methods that are able to provide more accurate results. However, because of the mathematical complexity introduced by the nonlinearities of the models, the nonlinear state estimation uses techniques that, in practice, are not so well-established which, leads to sub-optimal results. It is important to take into account that each method will have advantages and limitations when facing specific environments. The main objective of this paper is to provide a comprehensive overview and interpretation of the most well-known methods for nonlinear state estimation with Gaussian priors. In particular, the Kalman filtering methods: EKF (Extended Kalman Filter), UKF (Unscented Kalman Filter), CKF (Cubature Kalman Filter) and EnKF (Ensemble Kalman Filter) with an aerospace perspective.

Key Words
Kalman filter; nonlinear state estimation; Gaussian priors; aircraft/spacecraft tracking

Address
Milca F. Coelho, Kouamana Bousson and Kawser Ahmed:LAETA/UBI - AeroG, Laboratory of Avionics and Control, Department of Aerospace Sciences, University of Beira Interior, Covilha, Portugal

Abstract
The present study investigates axial vibration of a FG nanobeam using nonlocal elasticity theory under clamped-clamped and clamped-free boundary conditions. Power law, exponential law and sigmoid law are applied as grading laws to examine the effect of the material distribution on axial vibration of the FG nanobeam. A parametric study was done to examine the effect of length scale on the dynamic behavior of the structure and the results are presented. It was observed that consideration of the nonlocal length scale is essential when analyzing the free vibration of a FG nanobeam. The results of the present study can be used as benchmarks in future studies of FG nanostructures.

Key Words
nanobeam; functionally graded materials; axial vibration; nonlocal elasticity

Address
S. A. H. Hosseini: Department of Industrial, Mechanical and Aerospace Engineering, Buein Zahra Technical University, Buein Zahra, Qazvin, Iran

M. H. Noroozi Moghaddam and O. Rahmani: Smart Structures and New Advanced Materials Laboratory, Department of Mechanical Engineering, University of Zanjan, Zanjan, Iran

Abstract
Investigation of leading edge impingement cooling for first stage rotor blades in an aero-engine turbine, its effect on rotor temperature and trailing edge wake loss have been undertaken in this study. The rotor is modeled with the nozzle for attaining a more accurate simulation. The rotor blade is hollowed in order for the coolant to move inside. Also, plenum with the 15 jet nozzles are placed in it. The plenum is fed by compressed fresh air at the rotor hub. Engine operational and real condition is exerted as boundary condition. Rotor is inspected in two states: in existence of cooling technique and non-cooling state. Three-dimensional compressible and steady solutions of RANS equations with SST K-

Key Words
rotor blade; turbine cooling; jet impingement; heat transfer; CFD simulation; numerical

Address
Amin Peiravi, Mohsen Agha Seyyed Mirza Bozorg and Alireza Mostofizadeh: Department of Mechanical & Aerospace Engineering, Malek-Ashtar University of Technology, Isfahan, Iran

Abstract
To address the problems caused by the strong coupling of an airbreathing hypersonic vehicle's airframe and propulsion to the integrated control system design, an integrated airframe–propulsion model is established, and the coupling characteristics between the aircraft and engine are analyzed. First, the airframe–propulsion integration model is established based on the typical nonlinear longitudinal dynamical model of an air-breathing hypersonic vehicle and the one-dimensional dual-mode scramjet model. Thrust, moment, angle of attack, altitude, and velocity are used as transfer variables between the aircraft model and the engine model. The one-dimensional scramjet model can accurately reflect the working state of the engine and provide data to support the coupling analysis. Second, owing to the static instability of the aircraft model, the linear quadratic regulator (LQR) controller of the aircraft is designed to ensure attitude stability and height tracking. Finally, the coupling relationship between the aircraft and the engine is revealed through simulation examples. The interaction between vehicle attitude and engine working condition is analyzed, and the influence of vehicle attitude on engine safety is considered. When the engine is in a critical working state, the attitude change of the aircraft will not affect the engine safety without considering coupling, whereas when coupling is considered, the attitude change of the aircraft may cause the engine unstart, which demonstrates the significance of considering coupling characteristics.

Key Words
airframe-propulsion integration model; linear quadratic regulator; airframe-propulsion coupling characteristics; interaction between vehicle attitude and engine working condition

Address
Chengkun Lv, Juntao Chang, Yilei Dong and Jicheng Ma: Harbin Institute of Technology, 150001 Heilongjiang, People's Republic of China

Cheng Xu: Science and Technology on Complex System Control and Intelligent Agent Cooperation Laboratory, 100074 Beijing, People's Republic of China


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