Laminate bending and twisting actuation using piezoelectric laminae

Laminae of monolithic piezoceramic materials can supply a powerful bending actuation, but cannot supply twisting actuation because of their inherent symmetry. Polymeric piezoelectric materials possess the orthotropy required for both bending and twisting actuation, but are too compliant to provide a proper actuation. A piezoelectric ceramic/polymer matrix (PZT/Ep) composite lamina can provide the required stiffness and orthotropic symmetry for bending and twisting actuation. By using two PZT/Ep piezoelectric laminae, it is possible to construct a three-layer antisymmetric structure which can be actuated in pure bending, in pure twisting, or in any linear combination of bending and twisting. This antisymmetric laminate will, however, exhibit coupling of in-plane and out-of-plane responses. If this is undesirable, a symmetric laminate can be constructed which will uncouple these responses. This is illustrated using four piezoelectric laminae which can be actuated in pure bending, pure twisting, or any combination of bending and twisting. The important design variables are the PZT/Ep lamina orientation, stacking sequence (layer location), poling direction, and required voltage sources.