This paper reports an energy-based method for the dynamic pull-in instability analysis of a spherical dielectric elastomer (DE) balloon subjected to a quasi-statically applied inflation pressure and a Heaviside step voltage across the balloon wall. The proposed technique relies on establishing the energy balance at the point of maximum stretch in an oscillation cycle, followed by the imposition of an instability condition for extracting the threshold parameters. The material models of the Ogden family are employed for describing the hyperelasticity of the balloon. The accuracy of the critical dynamic pull-in parameters is established by examining the saddle-node bifurcation in the transient response of the balloon obtained by integrating numerically the equation of motion, derived using the Euler–Lagrange equation. The parametric study brings out the effect of inflation pressure on the onset of the pull-in instability in the DE balloon. A quantitative comparison between the static and dynamic pull-in parameters at four different levels of the inflation pressure is presented. The results indicate that the dynamic pull-in instability gets triggered at electric fields that are lower than those corresponding to the static instability. The results of the present investigation can find potential use in the design and development of the balloon actuators subjected to transient loading. The method developed is versatile and can be used in the dynamic instability analysis of other conservative systems of interest.

Polymer-based three-dimensional (3D) printing—such as the UV-assisted layer-by-layer polymerization technique—enables fabrication of deformable microstructured materials with pre-designed properties. However, the properties of such materials require careful characterization. Thus, for example, in the polymerization process, a new interphase zone is formed at the boundary between two constituents. This article presents a study of the interphasial transition zone effect on the elastic instability phenomenon in hyperelastic layered composites. In this study, three different types of the shear modulus distribution through the thickness of the interphasial layer were considered. Numerical Bloch-Floquet analysis was employed, superimposed on finite deformations to detect the onset of instabilities and the associated critical wavelength. Significant changes in the buckling behavior of the composites were observed because of the existence of the interphasial inhomogeneous layers. Interphase properties influence the onset of instabilities and the buckling patterns. Numerical simulations showed that interlayer inhomogeneity may result in higher stability of composites with respect to classical layup constructions of identical shear stiffness. Moreover, we found that the critical wavelength of the buckling mode can be regulated by the inhomogeneous interphase properties. Finally, a qualitative illustration of the effect is presented for 3D-printed deformable composites with varying thickness of the stiff phase.