Wang Z.-X.,Shanghai JiaoTong University |
Wang Z.-X.,Beijing Aeronautical Science and Technology Research Institute |
Xu J.,Beijing Aeronautical Science and Technology Research Institute |
Qiao P.,Shanghai JiaoTong University |
Qiao P.,Washington State University
Composite Structures | Year: 2014
A nonlinear analysis is presented for impact response of carbon nanotube-reinforced composite (CNTRC) structures under thermal conditions. Two plate configurations (i.e., single-layer and sandwich plates) are considered, and the nanotube reinforcement is either uniformly-distributed or functionally-graded in the plate thickness direction. The material properties of nanotube reinforced composites are estimated using micromechanical models. The equations of motion are based on a higher-order shear deformation theory with a von Kármán-type of kinematic nonlinearity, and the thermal effects are included by considering the nanotube reinforced composites as temperature-dependent. The equations of motion are solved with a two-step perturbation technique, and the initial stresses caused by either the thermal or in-plane edge loads as in-plane boundary conditions are introduced. The influences of material property gradient, volume fraction distribution, temperature change, initial stress, initial velocity of the impactor, and core-to-face sheet thickness ratio on impact response of plate structures are discussed. The analysis presented can help better understand the nonlinear impact response of functionally-graded materials and facilitate design and optimization of nanocomposite structures against impact and under thermal and other environments. © 2013 Elsevier Ltd.
Shen H.-S.,Shanghai JiaoTong University |
Wang Z.-X.,Beijing Aeronautical Science and Technology Research Institute
International Journal of Mechanical Sciences | Year: 2014
This paper deals with the large amplitude vibration, nonlinear bending and thermal postbuckling of functionally graded material (FGM) beams resting on an elastic foundation in thermal environments. Two kinds of micromechanics models, namely, Voigt model and Mori-Tanaka model, are considered. The motion equations are based on a higher order shear deformation beam theory that includes beam-foundation interaction. The thermal effects are also included and the material properties of FGMs are assumed to be temperature-dependent. The numerical illustrations concern the nonlinear vibration, nonlinear bending and thermal postbuckling of FGM beams resting on Pasternak elastic foundations under different thermal environmental conditions. It is found that the FGM beam with intermediate material properties does not necessarily have intermediate nonlinear frequencies. The thermal postbuckling path of simply supported FGM beams is no longer of the bifurcation type for both uniform and non-uniform temperature fields. © 2014 Elsevier Ltd.
Zhang J.,Beihang University |
Peng L.,Beihang University |
Peng L.,Beijing Aeronautical Science and Technology Research Institute |
Zhao L.,Beihang University |
Fei B.,Beihang University
International Journal of Fatigue | Year: 2012
The effect of delamination resistance on fatigue crack growth behavior of composite laminates is studied. The strain energy release rate normalized to fatigue delamination resistance (G cf) is proposed as a controlling parameter to evaluate the fatigue crack growth rates and thresholds. Compared to previously developed G cf determination method, the compliance approach presented in this paper shows obvious advantages, such as no interruption to the fatigue crack growth and independence on the specimen dimensions. Based on this approach, the fatigue delamination growth rates and thresholds of carbon/bismaleimide composite laminates under mixed I/II mode loadings are determined experimentally. © 2012 Elsevier Ltd. All rights reserved.
Tao R.,Beijing Institute of Technology |
Gao Z.,Beijing Aeronautical Science and Technology Research Institute |
Wang Y.,Beijing Institute of Technology
IEEE Transactions on Aerospace and Electronic Systems | Year: 2012
Based on the analysis of the side peaks in passive radar using digital video broadcasting-terrestrial (DVB-T) signal, two methods for the side peaks interference suppression are presented: the side peaks identification (SPI) method and the side peaks elimination-intersection (SPE-I) method. The SPI method identifies the side peaks by their positions and amplitudes relative to the main peaks. The SPE-I method eliminates the intra-symbol side peaks and the inter-symbol side peaks by preprocessing the reference signal respectively, and obtains the main peaks from the intersection of the peak positions in the two cross-ambiguity function (CAF) diagrams. The SPI method can identify the side peaks without the power loss and may lose the main peaks masked by the side peaks. The SPE-I method can eliminate the side peaks and detect the main peaks masked by the side peaks at the expense of the power loss. Combination of the SPI method and the SPE-I method can overcome their disadvantages. The proposed methods can avoid the false alarms of the side peaks and improve the target detection performance. © 1965-2011 IEEE.
Zhou Y.,Dublin Institute of Technology |
Jerrams S.,Dublin Institute of Technology |
Chen L.,Beijing Aeronautical Science and Technology Research Institute
Materials and Design | Year: 2013
For materials in modern machines, fatigue strength is probably the most critical physical property that needs to be understood. In particular, the high dynamic loading experienced by machine parts necessitates understanding fatigue properties in life limiting components. However, rubber fatigue is imperfectly understood and even less is known about fatigue resistance in adaptive or smart elastomers. Preliminary research into the equi-biaxial fatigue behaviour of magnetorheological elastomers (MREs) is described here. Test samples were fabricated by incorporating carbonyl iron particles, typically of 6-7μm in diameter, in room temperature vulcanised (RTV) silicone rubber. Physical testing was conducted using a bubble inflation testing system and test samples were fatigued at stress amplitudes between 0.75MPa and 1.4MPa under engineering stress control. S-N (Wöhler) curves of stress amplitude (σa=S) versus cycles to failure (N) are presented. Stress-strain behaviour throughout the fatigue process is also described. For a stress amplitude of 0.75MPa and zero minimum stress, stress softening was observed for the entire test, though it was particularly pronounced in the first 100 cycles of testing. A limiting value of complex modulus (E*), observed previously in dynamic testing of conventional elastomers, was determined in these tests. © 2013 Elsevier Ltd.
Wang C.H.,RMIT University |
Venugopal V.,RMIT University |
Peng L.,Beijing Aeronautical Science and Technology Research Institute
Journal of Adhesion | Year: 2015
The drive towards greater use of fiber-reinforced composites in primary structures, such as aircraft structures and wind turbines that are increasingly unitized, calls for advanced repair techniques that can restore the structural integrity and geometry. Two such repair techniques are stepped repairs and scarf repairs. Under certain conditions, stepped repairs are easier to perform than scarf repairs, but the step corners may cause high level of stress concentrations negatively affecting the strength of the repair. This paper presents an investigation of the effect of step corners on the fracture behavior of stepped joints under compressive loading, particularly after subjecting it impact damage. Joints featuring different corner radii were tested under compressive loading, and results showed that the impact damage reduced the compressive strength, to marginally below the compression-after-impact strength of composite laminates. The findings reveal that stepped repairs can be designed to rival the performance of scarf repairs, due to the similarity in the inherent stress concentrations at ply terminations in both repair configurations. © 2015 Taylor & Francis Group, LLC.
Li J.,Yu Da University |
Wang D.,Beijing Aeronautical Science and Technology Research Institute |
Peterson G.P.,Georgia Institute of Technology
Applied Thermal Engineering | Year: 2010
A thorough experimental investigation was carried out on a copper-water compact loop heat pipe (LHP) with a unique flat, square evaporator with dimension of 30 mm (L)×30 mm (W)×15 mm (H) and a connecting tube having an inner diameter of 5 mm. Using a carefully designed experimental system, the startup process of the LHP when subjected to different heat loads was studied and the possible mechanisms behind the observed phenomena were explored. Two main modes, boiling trigger startup and evaporation trigger startup, were proposed to explain the varying startup behavior for different heat loads. In addition, an expression was developed to describe the radius of the receding meniscus inside the wick, to balance the increased pressure drop along the LHP with increasing heat loads. Finally, insight into how the compact LHP can transfer heat loads of more than 600 W (with a heat flux in excess of 100 W/cm2) with no occurrence of evaporator dry-out was provided. © 2009 Elsevier Ltd. All rights reserved.
Wang J.,Beijing Aeronautical Science and Technology Research Institute
Multibody System Dynamics | Year: 2015
The paper develops a new type of geometrically exact beam element featuring large displacements and rotations together with small warping. The dimension reduction approach based on variational asymptotic method has been explored, and a linear two-dimensional finite element procedure has been implemented to predict the cross-sectional stiffness and recover the cross-sectional strain fields of the beam. The total and incremental variables mixed formula of governing equations of motion is presented, in which the Wiener–Milenković parameters are selected to vectorize the finite rotation. The dynamic problem of geometrically exact beam has been solved by the implicit Radau IIA algorithms, the time histories of large translations and rotations with small three-dimensional warping have been integrated. Numerical simulations have been performed and the results have been compared to those of commercial software LS-DYNA. It can be concluded that the current modeling approach features high accuracy and that the new geometrically exact beam with warping is robust enough to predict large deformations with small strain. © 2015 Springer Science+Business Media Dordrecht
Yang B.,Beijing Aeronautical Science and Technology Research Institute
Chinese Journal of Aeronautics | Year: 2013
The potential hazard resulting from uncontained turbine engine rotor blade failure has always been the long-term concern of each aero engine manufacturer, and to fully contain the failed blades under critical operating conditions is also one of the most important considerations to meet the rotor integrity requirements. Usually, there are many factors involving the engine containment capability which need to be reviewed during the engine design phases, such as case thickness, rotor support structure, blade weight and shape, etc. However, the premier method to demonstrate the engine containment capability is the fan blade-off test and margin of safety (MS) analysis. Based on a concrete engine model, this paper aims to explain the key points of aero engine containment requirements in FAR Part 33, and introduces the implementation of MS analysis and fan blade-off test in the engine airworthiness certification. Through the introduction, it would be greatly helpful to the industrial community to evaluate the engine containment capability and prepare the final test demonstration in engine certification procedure. © 2013 CSAA & BUAA. Production and hosting by Elsevier Ltd. All rights reserved.
Qi G.J.,Beijing Aeronautical Science and Technology Research Institute
Journal of Composite Materials | Year: 2011
Three-dimensional quartz fiber-reinforced silicon nitride composites were prepared by perhydropolysilazane (PHPS) infiltration and pyrolysis method, and the microstructures and interfacial reaction mechanisms were investigated by Fourier transform infrared spectrometer, solid-state 29Si MAS NMR spectrometer, field emission scanning electron microscope, and high-resolution transmission electron microscope (HRTEM). Strong interfacial adhesion was observed for the composites due to the formation of silicon oxynitrides in the fiber/matrix interfaces. HRTEM images of the composites after thermal treatment at 1873K showed a-cristobalite, α-Si3N4, and amorphous silicon oxynitrides, corresponding to crystallized quartz fibers, crystallized silicon nitride matrix, and noncrystalline interfacial phases. The interfacial reactions resulted from the silicon hydroxyl groups on the surfaces of quartz fibers and the active radicals in PHPS during infiltration and high-temperature pyrolysis. © The Author(s) 2010.