Embedded Shape Memory Alloy Fibers Research Articles

Micro-mechanics of composite with SMA fibers embedded in metallic/polymeric matrix under off-axial loadings

Abstract In this article, micro-thermo-mechanical response of composites with shape memory alloy (SMA) fibers surrounded by the metallic/polymeric matrix under multi-axial proportional/non-proportional loadings is investigated. A three-dimensional constitutive model with capability of the simulation of martensite transformation, reorientation of martensite variants, pseudo-elasticity and shape memory effects of SMA fibers is implemented. Elastic and elastic–plastic constitute equations are also utilized to characterize the mechanical behavior of polymer and metal matrices. The solution domain includes a representative volume element (RVE) consists of an SMA fiber surrounded by corresponding matrix in a square array arrangement. Finite element modeling of the prescribed RVE is developed based on the virtual work in the state of the generalized plane strain. Governing equations are solved by means of an incremental and iterative procedure with satisfying periodic boundary conditions. The effects of fiber volume fraction, off-axis angle, matrix material and pre-strain on the micro-thermo-mechanical behavior of composites with embedded SMA fibers subjected to various multi-axial proportional/non-proportional loadings are examined and discussed in detail. The results are reported for the first time and can be served as benchmark for future studies dealing with the analysis of macro composite structures consist of SMA fibers.

Vibration Analysis of Composite Plate Embedded with SMA Fibers

Shape Memory Alloy(SMA)has advantages of great recovery stress and elastic modulus varied with the temperature, so it can be embedded in composite structure to active control structure deformation and vibration. In this paper, we have deducted the recovery stress at different temperature by modifying the phase-change coefficient Ω of Liang Constitutive Model[1], then base on = /E equation, the recovery stress is translated into recovery strain. By using finite element software ANSYS, the natural frequency of composite plate at influence of recovery stress can be obtained under both ends of fixed conditions at three configurations. The steady-state vibration response of the composite plate embedded SMA fibers is also simulated. The results show that recovery stress of SMA can increase the natural frequency and can suppress vibration effectively.

Micromechanical prediction of the two-way shape memory effect in shape memory alloy composites

The two-way shape memory effect in monolithic shape memory alloys has been widely investigated both theoretically and experimentally. In the present study, this effect is analyzed for shape memory alloy composites by employing a micromechanical model. To this end, the responses of polymeric matrix and metal matrix unidirectional composites with embedded shape memory alloy fibers are determined. For the polymeric matrix composite, the effect of axial, transverse and shear loadings as well as the fiber volume fraction on the resulting two-way shape memory behavior are studied. The local distributions of stresses among the shape memory alloy fiber and epoxy matrix in the low- and high-temperature shapes of the composite are also investigated. Two training procedures that generate the two-way shape memory effect in the metal matrix composite are offered. The present analysis shows that the two-way shape memory effect in the chosen type of metal matrix composite is not as useful as in the polymeric matrix one. Finally, for a polymeric matrix composite that is subjected to a transverse normal loading, the effect of imperfect bonding between the shape memory alloy fibers and the neighboring matrix is investigated.

Nonlinear Bending of Composite Circular Plates with Embedded Shape Memory Alloy Fibers

Based on Brinson’s one-dimensional thermo-mechanical constitutive relations of shape memory alloys and the theory of thin plates in the von Kármán sense, the response of bending of a uniform heated circular plate embedded with SMA fibers in the radial directions and subjected to a uniform distributed mechanical load is studied. The characteristic curves of the central deflection versus temperature rise of the circular plate with both clamped and simply supported boundary conditions are obtained. The numerical results show that, the recovery forces of the pre-strained SMA caused by the phase transformation from martensite to austenite can modify the bending deformation significantly. So, it can be concluded that the bending deformation can be adjusted effectively and actively by embedment of the SMA fibers into the circular plates

Shape Memory Alloy Hybrid Composite Plates for Shape and Stiffness Control

Shape memory alloy hybrid composite plates are `intelligent' structures whose shape or stiffness is actively modified by embedded shape memory alloy fibers. In this work, the behavior of such structures is investigated numerically and experimentally. A finite element model which separately represents the host structure and the fibers in a two-dimensional setting is proposed as a simple tool to predict the structural behavior in stiffness and shape control. The shape control configuration is used to validate the model experimentally since it is the most sensitive to the choice of the geometrical and mechanical model parameters.

A Study of Interaction between Embedded SMA Fibers and Host Material

In this paper, a novel mechanics interaction model between embedded SMA (Shape Memory Alloy) wire and the host structure is presented. Integral equations for the displacement distribution along the interface of SMA wire and host structure are derived, and solutions are developed using the Kelvin elastic solution and the distribution of shear and normal stresses along the interface of SMA wire and host structure. The phase transformation of SMA material is divided into five consecutive phases and detailed description of the behavior of the embedded SMA wire in every phase is presented. Validity of this model is investigated by comparing the results from the present model with those obtained by the finite element analysis.

Development of Fe-Mn-Si-Cr Shape Memory Alloy Fiber Reinforced Plaster-Based Smart Composites

In previous studies, it has been found that the shape memory effect of the embedded straight and wavy shape memory alloy (SMA) fibers enhance the strength and energy absorption prior to fracture of the composite, where the embedded SMA fibers shrink due to their shape memory effect. In the case of wavy fiber reinforced composites, the SMA fibers were subjected to pre-tensile strain using fiber holder with rotatable rollers to maintain the constant periodicity and amplitude of wavy fibers. In this study, on the other hand, the wavy SMA fibers were subjected to pre-tensile strain without using fiber holder, and therefore, periodicity and amplitude of wavy fibers were varied during the deformation. Then the wavy SMA fiber reinforced smart composite is fabricated. For the mechanical property characterization, three-point bending test is performed for the specimens.

Vibration Characteristics and Optimization of Symmetric CFRP Laminates Containing Embedded Shape Memory Alloy Fibers.

In the present paper is examined the vibration characteristics and optimization of rectangular symmetric CFRP laminates containing embedded shape memory alloy (SMA) fibers. The recovery stress due to the shape memory effect of the SMA fibers and the concurrent mechanical property change are taken into consideration in the vibration analysis of the laminates when the embedded SMA fibers are activated. With the use of two in-plane and four out-of-plane lamination parameters, the fundamental frequencies of the activated laminates are discussed for the case that the laminates are simply supported at four edges, while the fundamental frequencies of the inactivated laminates are discussed with the use of four out-of-plane lamination parameters. Finally, the vibrational optimization problems of the CFRP laminates with embedded SMA fibers are examined by using a mathematical programming method in which the lamination parameters are used as design variables. The laminate configurations to realize the determined six lamination parameters are also discussed.

Damping Property of Epoxy Matrix Composite Beams with Embedded Shape Memory Alloy Fibers

In this present paper, an epoxy matrix composite beam with embedded SMA fibers of TiNi alloy are applied to improve the damping capacity of a beam in free vibration. In particular, an experimental method to measure the damping capacity of a beam structure using current control is proposed here. In addition, an analytical model of frequency vibration of a composite beam based on thermo-metallo-mechanical behavior due to electric heating in the SMA fiber is also proposed. The analytical results are compared with obtained experimental frequency data. Calculated and measured results illustrate the effects of current on the damping and frequency values.

The response of shape memory alloy composites

A microstructural model that couples the local and global effects is employed to analyse the behavior of composite materials with shape memory alloy fibers. Both metallic matrices and resin matrix composites with embedded shape memory alloy fibers are considered. Since shape memory alloys form fibers with large diameter, this model is particularly suitable for the analysis of this type of smart composite material where the coupling between the microstructural details and the macrostructure of the composite must be incorporated. Results are given that exhibit the response of composites with embedded shape memory alloy fibers in various circumstances.

Active flexible rods with embedded SMA fibers

Embedding of shape memory alloy (SMA) fibers in slender flexible bodies results in shape changes of the host medium, whenever shape recovery of the SMA fibers takes place. The shape change of a cylindrical rod with a single off-axis embedded SMA fiber is modeled. The distributed axial compressive force and bending moment due to phase transformation in the SMA fiber is evaluated using an approximate analytical model and the deformed shape of the flexible rod is found by solving the equations of equilibrium of the rod. The stability analysis for the linearized theory is carried out and the critical value of the phase transformation induced strain for buckling is evaluated.

Structural modification of simply-supported laminated plates using embedded shape memory alloy fibers

Shape memory alloy (SMA) fibers, and in particular Nitinol fibers, have been embedded in advanced composite materials to demonstrate numerous structural control/modification concepts. A large number of control concepts have been postulated, formulated and demonstrated by using the unique control parameters available from Nitinol fiber actuators. Several new paradigms for structural design and control have resulted from the unusual behavior and mechanical properties of SMA. A brief introduction to SMA, laminated composite plates with embedded SMA fibers and a description of some of the available control parameters is presented. A linear analysis for a simply-supported symmetrically laminated composite plate embedded with SMA fibers using the Rayleigh-Ritz method is presented. Results of deflection, free vibration, buckling, and structural acoustic control are discussed. Two novel structural control techniques, active strain energy tuning (ASET) and active property tuning (APT), are highlighted and the authority of each technique demonstrated.