Thermomechanical Response of SMA Composite Beams with Embedded Nitinol Wires in an Epoxy Matrix

Abstract

Nitinol shape memory wires were embedded in epoxy beams to study their thermomechanical behavior in the embedded state. Beams were made with ten wires placed below the geometric mid-plane. A room temperature cure epoxy was used to minimize residual stresses acting on the wires. The beams were placed in an oven and heated from room temperature to a temperature well above the austenitic finish temperature of the wires. The beams were photographed through a window in the oven door at periodic intervals during the experiment. The photographs were analyzed to measure beam deflections during the experiment resulting from thermal and shape memory transformational strains. A beam model was developed and predictions of beam curvature were compared to the experimental data. The results show that agreement between the model and the experimental data is dependent, and extremely sensitive to, an accurate knowledge of the thermomechanical properties of both the nitinol and epoxy phases. Large deflections of the beams were obtained and some evidence of a transformation front propagation from the edges to the center of the beam is shown.

Two-way Antagonistic Shape Actuation Based on the One-way Shape Memory Effect

“…Many reversible, SMA-actuated structures based on this principle have been designed and tested. One approach has embedded one-way SMA wires or ribbons in polymers whose elastic deflection provides the restoring force (Pfaeffle et al, 1993;White and Berman, 1998;Baz et al, 2000). A second approach has one-way SMA elements directly attached to shape changing structures containing elastic members (e.g., springs) for shape restoration (Beauchamp et al, 1992;Kudva et al, 1996;Van der Wijst et al, 1997, Strelec andLagoudas, 2002).…”

Shape changes by coupled bending and twisting of shape-memory-alloy-embedded composite beams

“…In figure 3, the numerical results from the present model are compared with the experimental results of White and Berman [15] to validate the method and computer code developed in this study. For realistic comparison, all conditions such as beam materials and dimensions and wire locations were set to be the same as in [15].…”

“…However, efforts to control the shapes of SMA-embedded composite structures are quite rare. Even though some do exist, the hosting materials were not structural [5,6]. Some works were only concerned with the dynamic responses of composite structures with embedded SMA wires.…”

Review and perspectives: shape memory alloy composite systems

“…Shape memory alloy reinforced composites were also considered as promising candidates for morphing structures. Composite actuators in the form of beams and rods were first analyzed by Chaudhry and Rogers [83] and Lagoudas and Tadjbakhsh [241,242], respectively, and subsequent efforts focused on characterizing the actuation response of SMA composites soon followed [449,33,60] (including SMA-piezoelectric systems [235,236]). Over the years, actuators comprised of SMA composites have been extended from simple engineering configurations (e.g., rods and beams) to complex structures.…”