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Recently, temperature-sensitive hydrogels have been employed widely in various applications such as switches and actuators. Considering the discontinuity in the stresses and deformation fields of multilayers, in this article, we developed a new analytical method to study the swelling-induced finite bending of temperature-sensitive functionally graded hydrogels under plane-strain condition. The cross-linked density distribution along strip thickness varies linearly or exponentially which causes the switch to bend in response to temperature variation. To clarify the actuation mechanism and probe the various effects of parameters on switches’ thermomechanical response, a semi-analytical approach is developed. Finite element method is employed to validate the deformation of functionally graded temperature-sensitive hydrogel layer results. The stresses and deformation fields, bending curvature, and semi-angle are investigated using semi-analytical and numerical methods for several cases in one-directional and bidirectional bending switches. The continuous stresses and deformation fields and multiple neutral axes are illustrated which have crucial role in designing switches.

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In this paper, coupled axial and torsional large deformation of an incompressible isotropic functionally graded nonlinearly elastic solid cylinder is investigated. Utilizing stretch-based constitutive models, where the deformation tensor is non-diagonal is complex. Hence, an analytical approach is presented for combined extension and torsion of functionally graded hyperelastic cylinder. Also, finite element analysis is carried out to verify the proposed analytical solutions. The Ogden model is employed to predict the mechanical behavior of hyperelastic materials whose material parameters are function of radius in an exponential fashion. Both finite element and analytical results are in good agreement and reveal that for positive values of exponential power in material variation function, stress decreases and the rate of stress variation intensifies near the outer surface. A transition point for the hoop stress is identified, where the distribution plots regardless of the value of stretch or twist, intersect and the hoop stress alters from compressive to tensile. For the Ogden model, the torsion induced force is always compressive which means the total axial force starts from being tensile and then eventually becomes compressive i.e., the cylinder always tends to elongate on twisting.

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