Deformations of flexible and foldable electro-active composite structures

Abstract

This paper presents numerical analyses of elastic and viscoelastic smart flexible and foldable composite structures under electric field actuation. The studied composites comprise of multiple distributed piezoelectric patches bonded to the surfaces of inactive thin planar structures (substrates). Upon applications of electric field input, the planar structures can undergo three-dimensional large rotational deformations while their strains and stretches remain relatively small. A nonlinear time-dependent electro-mechanical coupling relation for the piezoelectric patches is considered to simulate more precisely response of piezoelectric materials when subjected to large magnitude of electric field. Co-rotational Lagrangian finite element approach is used for solving the governing equations of the deformations of flexible and foldable electroactive composite structures. Various three-dimensional shape changes of originally planar structures are achieved with different arrangements of integrated patches and subjected to different magnitude of electric fields. The effect of viscoelastic substrates and time-dependent electro-mechanical coupling of piezoelectric materials on the deformed shapes is also studied. This analysis can help designers in simulating desired deformed shapes and determining external stimuli to be prescribed prior to fabricating smart and flexible composites.

Modeling and simulation of thermally actuated bilayer plates

“…However, high contrast in mechanical properties, i.e., elastic modulus, between the two layers can induce high stress discontinuities between the layers, leading to delamination. Another mechanism for 2 S. BARTELS, A. BONITO, A. H. MULIANA, AND R. H. NOCHETTO folding and bending of bilayers can be achieved by integrating two electroactive polymers with the opposite directions of through-thickness poling axes and when the bilayers are subjected to electric potential through the thickness one layer would expand while the other would contract [31,30,21]. One of the advantages of combining two polymers with different responsive characteristics with regard to their non-mechanical performances is that the mechanical properties of polymers do not vary significantly, e.g., extensional elastic moduli of various polymers are typically between 0.5−5.0 GPa, which can minimize stress discontinuities at the interfaces between the two layers and thus can avoid failure due to delamination.…”

“…We are specifically interested in bilayers comprising of two polymeric layers that can undergo large deformations when exposed to non-mechanical stimuli, such as temperature changes or fluid sorption. Due to the slender nature of the bilayers, large deformations are mainly governed by rotations while the strains in the bilayer are relatively small [26,30], thereby leading to negligible stretching and transverse shear effects. Furthermore, the mid-surface of the bilayer plate is considered to be inextensible and non-shearable, thereby leaving bending as a chief mechanism for shape deformation.…”

Modeling and Simulation of Thin Layered Composites Under Non-mechanical Stimuli

“…For this purpose, a homogeneous planar surface out of the inactive layer (substrate) is considered and external moments to the planar surface are prescribed. A co-rotational (CR) finite element approach, which splits the large rotation from the in-plane deformations, following Felippa and Haugen (2005) and Tajeddini and Muliana (2017), is used in order to determine the shape reconfiguration of the substrate. This approach is considered since prescribing non-mechanical stimuli only cause free expansion/contraction in the active layer and the substrate does not undergo free expansion/contraction due to an application of the nonmechanical stimuli.…”

“…Swelling regions, which govern the folding shapes, are modeled by changing the length of the bond in the active networks (swelled regions). Finite element method has been used to simulate large deformation shape reconfigurable in multilayered 2D planar surfaces activated with various stimuli (e.g., Mailen et al, 2015;Tajeddini and Muliana, 2017;Bartels et al, 2018). Bartels et al (2018) also discussed the occurrence of corner folding (termed as dog ears) of planar surfaces instead of folding into desired cylindrical shapes, which is attributed to a slow diffusivity process.…”

Effects of soft and hard magnetic particles on the mechanical performance of ultra-soft magnetorheological elastomers

“…Smart materials are bringing sweeping changes in the way humans interact with engineering devices. A myriad of state-of-the-art applications are based on novel ways to actuate on structures that respond under different types of stimulus such as light [81], temperature [33,82], electricity [70,21], changes in the pH [85] and magnetic fields [36,24]. Among them, materials that respond to magnetic stimuli enable to remotely modify their mechanical characteristics and macroscopic shape.…”