دانلود رایگان مقاله تغییر شکل ساختار کامپوزیت الکترو فعال انعطاف پذیر و تاشو

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 in-active 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 electro-active 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.

5. Conclusion

Deformation analyses of smart flexible and foldable electroactive composites have been performed in this study. The composite structures comprise of thin planar substrates integrated with piezoelectric actuators perfectly bonded to the top and bottom surfaces of the substrates. The actuators considered here are piezoelectric ceramics, which is elastic, and AFC, which is viscoelastic. Nonlinear electro-mechanical responses are considered for both piezoelectric ceramics and AFC since for actuating purposes relatively large electric field is often prescribed. Viscoelastic behaviors are considered for the polymeric substrates. By prescribing electric field inputs to the actuators the planar composite structures can be formed into three-dimensional shapes predominantly by rotations while the in-plane strains and stretch remain small. The CRFE method has been adopted for the large deformation analyses of the electro-active composite structures. Several arrangements of piezoelectric patches and different history of electric field inputs have been considered in order to obtain various shape changes in the planar structures. The effects of viscoelastic substrates and nonlinear electro-mechanical coupling properties on the deformed shapes have been examined. It is concluded that when elastic piezoelectric patches, such as piezoelectric ceramics, are bonded to viscoelastic substrates the time-dependent deformations in the overall structures are negligible since the resulting bending moments required to induce rotations to the structures decrease simultaneously with stress relaxation in the viscoelastic substrates. However, significant time-dependent deformations are observed when the viscoelastic AFC patches are considered, in which the structures continue to experience shape changes even after the electric field input is completely prescribed. The nonlinear electro-mechanical coupling behaviors of the actuators significantly influence the deformed shapes of the structures. The presented methods and examples of boundary value problems discussed in this study can help designers in simulating desired deformed shapes and determining placements of piezoelectric patches external stimuli to be prescribed prior to fabricating smart and flexible composites. The analyses can also help in selecting materials for both substrates and actuators during the design of foldable and flexible composite structures.