Shape Memory Alloy Volume Fraction Research Articles

Pseudo-elastic hysteresis damping characteristics of SMA hybrid composite lamina

The longitudinal mechanical behavior of shape memory alloy (SMA) composite lamina subjected to longitudinally strain or stress controlled cyclic loading is investigated. The SMA is under pseudo- elastic condition and the fibers are embedded (bonded) to the host material. The influences of temperature, volume fraction of SMA and longitudinal modulus of the host material on the stress-strain relation and energy dissipation of the SMA hybrid composite lamina are discussed. The results indicate that the stress-strain curve of the lamina per cycle shows a hysteresis loop. The hysteresis damping decreases with increasing temperature and with decreasing volume fractions of SMA. In addition, the hysteresis damping is nearly independent of the longitudinal modulus of the host material under strain controlled loading. However, it depends dramatically on the longitudinal modulus of the host material under stress controlled loading, which shows the SMA composite lamina has high pseudo-elastic hysteresis damping when the longitudinal modulus of the host material is low.

Low-velocity impact response of active thin-walled hybrid composite structures embedded with SMA wires

Effect of some important parameters on low-velocity impact response of the active thin-walled hybrid composite plates embedded with the shape memory alloy (SMA) wires is investigated in this paper. The interaction between the impactor and the composite plate is considered in the impact analysis. The SMA wires are embedded within the layers of the composite laminate. The effect of the SMA wires on contact force history, deflection, in-plane strains and stresses of the structure was studied. The first-order shear deformation theory as well as the Fourier series method is utilized to solve the governing equations of the composite plate analytically. The interaction between the impactor and the plate is modeled with the help of two degrees-of-freedom system, consisting of springs-masses. The Choi's linearized Hertzian contact model is used in the impact analysis of the laminated hybrid composite plate. The results indicate that some of the important geometrical and physical parameters like the SMA volume fraction, orientation of composite medium fibers, impactor mass, impactor velocity, and length-to-thickness ratio of the plate ( a/h ratio) are important factors affecting the impact process and the design of structures.

RANDOM RESPONSE OF SHAPE MEMORY ALLOY HYBRID COMPOSITE PLATES SUBJECT TO WHITE-GAUSSIAN NOISE AND THERMAL ENVIRONMENT

The random response and thermal buckling of a traditional composite plate impregnated with pre-strained shape memory alloy (SMA) fibers subjected to combined thermal and acoustic loads are investigated using a finite element model based on the first order shear deformable plate theory and von Karman strain-displacement relations to account for moderately large deflection. The thermal load is assumed to be steady state constant temperature distribution, and the acoustic excitation is considered to be a stationary Gaussian pressure with zero mean and uniform magnitude over the plate surface. The governing nonlinear equations are obtained using the principal of virtual work adopting an approach based on the thermal strain being an integral quantity of the thermal expansion coefficient with respect to temperature to account for temperature dependent material properties. The static nonlinear equations are solved by Newton-Raphson numerical technique to get the thermal post-buckling deflection. The dynamic nonlinear equations of motion are transferred to modal coordinates to reduce the computational efforts. The Newmark implicit integration scheme is employed to solve the second order ordinary differential equations of motion. Finally, the buckling temperature, post-buckling deflection and the random response of a SMA hybrid composite plate panel are presented, illustrating the effect of SMA volume fraction, pre-strain, sound pressure level and temperature rise on the panel response.

Natural frequencies of a multilayer SMA laminated composite cantilever plate

This paper presents a finite-element model for the free vibration analysis of a shapememory alloy (SMA) surface laminated composite cantilever plate. The proposed device isconsidered to undergo small displacements and small strains. The governing equations aredeveloped utilizing the first-order shear deformation theory, energy balance equations andtwo-dimensional model of the SMA layer. The finite element is modelled using first-ordershear deformation theory and equivalent single-layer assumptions. The plate isconsidered with clamped-free boundary conditions, and the SMA layer is at thetop of the composite plate. Parametric studies are conducted to study the effecton free vibration of varying the SMA volume fraction, the temperature of theSMA, and the thickness, width and stiffness of the composite cantilever plate.

Vibration characteristics of laminated composite plates with embedded shape memory alloys

Shape memory alloy (SMA) is commercially available for a variety of actuator and damping materials. Recently, SMA wires have also become commercially available for the design of smart composite structures because SMA wires with a small diameter can be easily produced. In this work, two types of SMA-based composites are presented for investigating the vibration characteristics. First, laminated composite plates containing unidirectional fine SMA wires are fabricated. By measuring the vibration mode of a clamped cantilever, the influence of both SMA arrangement and temperature on the vibration characteristics is made clear. Next, laminated composite plates with embedded woven SMA layer are fabricated. The stiffness tuning capability is evaluated by impact vibration tests with different temperatures. It is found that the stiffness tuning capability may be improved by increasing the volume fraction of SMAs and by controlling accurately the internal stress according to the phase transformation temperature of SMAs from martensite to austenite. The theoretical prediction on the natural frequency considering the SMAs behavior and laminated structures is proposed and their results agree reasonably with experimental ones.

Thermal Buckling Suppression of Supersonic Vehicle Surface Panels Using Shape Memory Alloy

An efficient finite element method for the prediction of critical temperature, postbuckling deflection, and vibration characteristics is presented for traditional composite plates embedded with prestrained shape memory alloy (SMA) wires. The temperature-dependent material properties of SMA and composites and the large deflections are considered in the formulation. An iterative eigensolution is presented to determine the critical temperature, the Newton-Raphson method is employed to obtain postbuckling large deflection, and the eigensolver is used to predict free vibration frequencies about the thermally buckled equilibrium positions. Results show that the critical buckling temperature can be raised high enough and that the postbuckling deflection can be completely suppressed for surface panels of supersonic vehicle applications by the proper selection of SMA volume fraction, prestrain, and alloy composition. Weight savings based on critical temperature in the use of SMA as compared with the traditional composite and titanium plates are demonstrated.

Micromechanical Modelling of Shape Memory Alloy Composites

AbstractAn isothermal finite element method (FEM) model has been applied to study the behavior of two kinds of shape memory alloy (SMA) composites. For SMA‐fiber reinforced normal metal composites, the FEM analysis shows that the mechanical behavior of the composites depends on the SMA volume fraction. For normal metal‐fiber reinforced SMA matrix composites, the SMA phase transformation is affected by the increasing Young’s modulus of the metal fiber. The phase transformation was also treated using a simple numerical analysis, which assumes that there are uniform stresses and strains distributions in the fiber and the matrix respectively. It is found that there is an obvious difference between the FEM analysis and the simple numerical assessment. Only FEM can provide reasonable predictions of phase transformations in SMA/normal metal composites.

Role of Microstructure in the Thermomechanical Behavior of SMA Composites

A numerical study on the role of microstructure in the thermomechanical behavior of shape memory alloy (SMA) composites under uniaxial tension is performed. The simulation is based on the micromechanics model established recently by the authors. The influence of the shape and volume fraction of SMA on the overall behavior of the composite as well as on the internal stress and strain evolution is investigated. The strengthening effect of SMA on ductile matrix is illustrated. The obtained results demonstrate several interesting features of the new composite and may serve as a quantitative basis for the microstructure design of this composite in the future.

Material Damping Analysis of Smart Hybrid Composite Laminated Plate Structures

Material damping analysis of a generally laminated smart hybrid composite plate has been presented in this paper. The present analytical formulation is an integrated micro-macromechanical method. Analytical equations derived at the lamina level together with a classical laminated thin plate theory predict the equivalent material specific damping capacity (SDC) of a general smart hybrid composite laminated plate structure. The micro-niechanical equations based on the mechanics of material have been used for the calculation of the elastic stiffness and SDC ot an intraply hybrid composite lamina. Present objective is mainly to get a first hand information on the basic material damping behavior of hybrid composite laminate. Therefore, numerical studies have been carried out for a typical shape memory alloy (SMA) smart composite laminated plate model. The effects of the laminate fiber orientaton and the SMA volume fraction on the SDC and natural frequencies of the laminate were evaluated.