Active plate and wing research using EDAP elements

Abstract

The deflection characteristics of structures using directionally attached piezoelectric (DAP) and enhanced DAP (EDAP) elements are explored. Tests demonstrate that piezoceramic elements, which are isotropic, exhibit orthotropic behavior when directionally attached using any of three methods: (i) partial attachment, (ii) transverse shear lag, and (iii) differential stiffness bonding. Test results demonstrate that directional enhancement through transverse stiffening can increase DAP element strain from 5 to 25%. Closed form expressions of DAP/EDAP strains based on classical laminated plate theory are presented. The models demonstrate that DAP/EDAP elements generate any in-plane strain (extensions and shear) or out-of-plane curvature (bending in either direction and twist) independent of other strains or curvatures. Test results show that fiberglass and aluminium DAP/EDAP beams produce torsional and bending deflections in excess of 30° m^-1 with theory and experiment in close agreement. The deflections of DAP/EDAP and conventional piezoelectric active structures are compared. Tests show that DAP/EDAP elements can produce up to 16 times more twist than conventionally attached piezoceramic elements. Two wings were constructed with DAP and EDAP elements. EDAP elements were laminated into the skin of a graphite/epoxy supersonic wing that had a 9% thick diamond airfoil section and an aspect ratio of 3. DAP elements were also laminated to a torsion beam of a subsonic wing that had an NACA 0012 profile and an aspect ratio of 1.4. The supersonic wing demonstrated static twist deflections in excess of 2°. The subsonic wing demonstrated static pitch deflections of 9°. The lifting capability of the DAP/EDAP wings are compared to piezo-ailerons. The DAP/EDAP wings are shown to produce much larger changes in lift coefficient and greater deflection stability with increasing airspeed than the piezo-aileron configuration.