Active Stiffening of Composite Materials by Embedded Shape-Memory-Alloy Fibres

1996 ◽  
Vol 459 ◽  
Author(s):  
J.-E. Bidaux ◽  
J.-A. E. Månson ◽  
R. Gotthardt
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Vibration Frequency ◽  
Composite Beam ◽  
Natural Vibration ◽  
Transformation Strain ◽  
Natural Vibration Frequency ◽  
The Matrix ◽  
Clamping Device ◽  
Composite Response

ABSTRACTThe use of shape-memory-alloy (SMA) fibres to actively changethe stiffness of a composite beam is investigated on a model system composed of an epoxy matrix with a series of embedded pre-strained NiTi fibres. Stiffness changes are detected through shifts in the natural vibration frequency of the beam. When electrically heated, the pre-strained NiTi fibres undergo a phase transformation. Since the shape recovery associated with the transformation is restrained by the constraints of both the matrix and the clamping device, a force is generated. This force leads to an increase in the natural vibration frequency of the composite beam. Depending on the degree of fibre pre-strain, either ordinary martensite, R-phase or a mixture of the two can be stress-induced. It is found that the R-phase gives rise to the largest change in vibration frequency for a given temperature increase and the most reversible behaviour. Its low transformation strain is also more favourable for fibre-matrix adhesion. The effect of stress relaxation in the polymer matrix on the composite response is discussed.

Conceptual design and numerical studies of active flow control aerofoil based on shape-memory alloy and macro fibre composites

2021 ◽  
Vol 125 (1287) ◽  
pp. 830-846
Author(s):  
W. Zhang ◽  
X.T. Nie ◽  
X.Y. Gao ◽  
W.H. Chen
Keyword(s):  
Shape Memory Alloy ◽  
Flow Control ◽  
Shape Memory ◽  
Vibration Frequency ◽  
Active Flow Control ◽  
Flow Characteristics ◽  
Hybrid Design ◽  
Numerical Studies ◽  
Fibre Composites ◽  
Active Flow

ABSTRACTActive flow control for aerofoils has been proven to be an effective way to improve the aerodynamic performance of aircraft. A conceptual hybrid design with surfaces embedded with Shape-Memory Alloy (SMA) and trailing Macro Fibre Composites (MFC) is proposed to implement active flow control for aerofoils. A Computational Fluid Dynamics (CFD) model has been built to explore the feasibility and potential performance of the proposed conceptual hybrid design. Accordingly, numerical analysis is carried out to investigate the unsteady flow characteristics by dynamic morphing rather than using classical static simulations and complicated coupling. The results show that camber growth by SMA action could cause an evident rise of Cl and Cd in the take-off/landing phases when the Angle-of-Attack (AoA) is less than 10°. The transient tail vibration behaviour in the cruise period when using MFC actuators is studied over wide ranges of frequency, AoA and vibration amplitude. The buffet frequency is locked in by the vibration frequency, and a decrease of 1.66–2.32% in Cd can be achieved by using a proper vibration frequency and amplitude.

Study on the Influence of Reactor Core Structure on Reactor Natural Vibration Frequency

2021 ◽  
Author(s):  
Yuan Zhou ◽  
Tian Tian ◽  
Xiongfei Yu ◽  
Ran Ren ◽  
Liangcai Zhou ◽  
...  
Keyword(s):  
Vibration Frequency ◽  
Natural Vibration ◽  
Reactor Core ◽  
Core Structure ◽  
Natural Vibration Frequency

scholarly journals Analysis of the natural oscillation frequency of the long-span trusses with flanged connections

2021 ◽  
pp. 76-85
Author(s):  
Татьяна Георгиевна Рытова ◽  
Людмила Анатольевна Максимова ◽  
Анастасия Георгиевна Николаева ◽  
Татьяна Михайловна Макарова ◽  
Надежда Георгиевна Пфаненштиль
Keyword(s):  
Dynamic Characteristics ◽  
Vibration Frequency ◽  
Natural Vibration ◽  
Natural Oscillation ◽  
Natural Vibration Frequency ◽  
Building Structures ◽  
Long Span ◽  
Local Areas ◽  
Calculation Results ◽  
Natural Oscillation Frequency

Приводится анализ частоты собственных колебаний большепролетной фермы с фланцевыми соединениями. Выполнен расчет фланцевого соединения с различными случаями исключения болтов из работы соединения. Анализ результата расчета показал, что возникновение повреждений и дефектов конструкций здания в локальных зонах, величина которых несущественно снижает общую жесткость каркаса, практически не влияет на динамические характеристики каркаса. The analysis of the natural vibration frequency of a large-span truss with flanged connections is given. The calculation of the flange connection with various cases of exclusion of bolts from the connection operation is performed. Analysis of the calculation results showed that the occurrence of damage and defects in the building structures in local areas, the value of which significantly reduces the overall rigidity of the frame, practically does not affect the dynamic characteristics of the frame.

Shear Load Transfer in Shape Memory Alloy Fiber Reinforced Composites During Elastic Axisymmetric Deformations

2000 ◽  
Author(s):  
Hungyu Tsai ◽  
Xinjian Fan
Keyword(s):  
Phase Transformation ◽  
Stress Concentration ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Transition Layer ◽  
Load Transfer ◽  
Fiber Reinforced Composites ◽  
Shear Load ◽  
Reinforced Composites ◽  
The Matrix

Abstract The axisymmetric elastic deformations in shape memory alloy (SMA) fiber reinforced composites are studied. We analyze the stress concentration near the interface between the fiber and the matrix as a result of a pre-described phase transformation in the active fiber. A typical model involving a single infinite fiber embedded in an infinite elastic matrix is studied. A portion of the fiber is allowed to undergo phase transformation along the axial direction so that its length is changed by the corresponding transformation strain (typically a few percentages), while the matrix is assumed to be linearly elastic and isotropic. Under certain bonding conditions, the deformation of fiber forces the matrix to deform in the elastic regime in order to accommodate the transformation strains. The problem is formulated as axisymmetric deformations coupled with a finite transformation region in the fiber. In order to avoid infinite stresses found under perfect bonding conditions, we adopt a “spring” model which accounts for the elasticity of a transition layer at the interface. This model allows for relative displacements between the fiber and the matrix. A linear relation between this relative displacement and the shear stress is used. The exact elasticity solution (in integral form) to this problem is found using Love’s stress function and Fourier transform. Numerical integration is performed to produce the stress distributions. In particular, the shear load transfer profiles along the interface are calculated for various spring stiffness. It is found that the singularity is eliminated and the stress concentration factor depends on the stiffness of the transition layer.

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