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

Shape memory alloys (SMAs) have demonstrated the potential for various smart structure applications. SMAs undergo a reversible phase transformation from martensite to austenite as temperature increases. This transformation leads to shape recovery and associated recovery strains. If SMA actuators are embedded off the neutral surface and are oriented at arbitrary angles with respect to a beam axis, then the beam bends and twists due to the coupling effects of recovery strains activated. In this study, the shape changes by bending and twisting of a SMA/graphite/epoxy beam controlled by both electric resistive heating and passive elastic tailoring were investigated. Three-dimensional finite-element formulations were derived and validated to analyze the responses of the SMA/composite beam. Numerical results show that the shape of the SMA/graphite/epoxy composite beam can be controlled by judicious choices of control temperatures, SMA angles and elastic tailoring.