Sep 4, 2017 - [3] Schultz, Marc R., W. Keats Wilkie, and Robert G. Bryant. "Investigation of self-resetting active multistable laminates." Journal of aircraft ...
ICCS20 - 20th International Conference on Composite Structures, Paris, France, September 4 – 7, 2017 A.J.M. Ferreira (Editor)
Snap-through of Multistable Variable Stiffness Composites using Piezoelectric Actuators Ayan Haldar, Eelco Jansen, Raimund Rolfes Leibniz Universitaet Hannover, Institute of Structural Analysis, Appelstrasse 9A, 30167 Hannover, Germany Abstract As multistable structures are intended to be used in morphing applications, the phenomenon of snapping from one stable state to another is of paramount importance. For instance, if the snapping loads are relatively high, morphing action would be difficult to achieve or may require several actuators, which is contrary to the weight requirements. Variable stiffness (VS) composites possess a rich design space of multistable configurations that demonstrate different out-of-plane displacements and curvatures [1]. Exploiting the variable directional stiffness of the VS composite may yield certain designs that require low snap-through forces. Such VS laminates could significantly reduce the actuator size but still be capable of morphing under large deflections. In recent years, Macro Fiber Composite (MFC) Actuators have proven to be an efficient way to allow snap-through from one stable shape to another [2, 3]. Schultz et al. [3] successfully demonstrated the use of MFCs for the snap-through as well the snap-back process. In the present work, the snap-through and the snap-back phenomena of VS laminates are investigated by using MFC patches on top and bottom of the laminate. A semi-analytical model developed earlier in [1] is extended where the effect of piezoelectric actuators is considered. The fiber orientation of the layers of the VS laminate is assumed to vary linearly from the center to the edge of the plate as proposed by Gürdal et al. [4]. The formulated semi-analytical model provides a deeper insight on the dependence of different angle parameters in a VS laminate and gives the input voltage required to trigger snap-through to another stable shape. To complement the semi-analytical results, a nonlinear finite element analysis is performed by attaching piezoelectric actuators on both surfaces of the VS laminate. An electric field is applied to one of the actuators to trigger snap-through from one stable shape to another. Similarly, the snap-back process is simulated by actuating the other MFC patch. Results from the both semianalytical and FE analysis are compared. Certain configurations of VS laminates are found which have bistable shapes with high out-of-plane displacement but require smaller actuators for snap-through and snap-back than the conventional straight fiber laminates.
ICCS20 - 20th International Conference on Composite Structures, Paris, France, September 4 – 7, 2017 A.J.M. Ferreira (Editor)
References [1] Haldar, Ayan, José Reinoso, Eelco Jansen, and Raimund Rolfes. "Thermally induced multistable configurations of variable stiffness composite plates: Semi-analytical and finite element investigation." Composite Structures (2017), Accepted Manuscript. [2] Tawfik, Samer A., D. Stefan Dancila, and Erian Armanios. "Unsymmetric composite laminates morphing via piezoelectric actuators." Composites Part A: Applied Science and Manufacturing (2011): 748-756. [3] Schultz, Marc R., W. Keats Wilkie, and Robert G. Bryant. "Investigation of self-resetting active multistable laminates." Journal of aircraft (2007): 1069-1076. [4] Gürdal, Zafer, Brian F. Tatting, and C. K. Wu. "Variable stiffness composite panels: effects of stiffness variation on the in-plane and buckling response." Composites Part A: Applied Science and Manufacturing (2008): 911-922.
