Investigation On Macro-fiber Composites Based Twisted Wing Structures

While smart morphing wings have become one of the international research hottopics, as one important branch of those smart morphing wings, the smart twisted winghas been discussed a lot by those foreign experts, but we Chinese have done little onthis topic, no one has been able to put forward a feasible smart twisted wing structures.This paper tries to breakthrough in this regard. A smart twisted wing structure isproposed that uses piezoelectric macro-fiber composites (MFC) as actuators, withnegative poisson’s ratio honeycomb as aerodynamic pressure support structures, andwith the flexible skin maintain its aerodynamic shape.The leading edge and the trailing edge will be exchanged when rotor/wing inconversion, thus requires the leading edge and the trailing edge must be symmetrical. Aairfoil like that is called elliptic airfoils. While we can’t get a proper elliptic airfoil fromthe airfoil library, so the elliptic airfoil used in this paper should be designed. In thispaper, a elliptic airfoil is designed whose maximum relative thickness is10.74%andmaximum amount of camber is1.59%, both happened on the50%chord edge. Set theReynolds number is420000, use the Fluent Spalart-Allmaras model calculate theelliptic airfoil’s lift-drag performance. Under the same attack angle, when compared toother commonly used low-speed airfoil, the elliptic airfoil get smaller lift coefficientand larger drag coefficient.The second part of this paper is the smart twisted wing frame structure design. Useeight pieces of MFC materials as the drive, and stick them to the support plate in themiddle of the frame structure, thus obtain the MFC smart structure. A test is executed todetermine the twist ability of the MFC smart structure. to carried on the experimentaldetermination to the reverse. Its largest twist angle is about9.3°, obtained whenelectrified at the maximum operating voltage1500V DC.The third part of this paper centers on the negative possion’s ratio honeycomb.Take its cell as the analysis model to make the in-plane deformation theory analysis.Thus obtain the relationship between the mechanical properties and the cell’s geometricparameters. Set the possion’s ratio of the honeycomb as-1to execute the preparation ofexperimental honeycomb. Use aramid paper and epoxy resin as raw material, the elasticmodulus of the made aramid paper-epoxy laminated membrane is about978.61MPa,and its tensile strength is about28.93MPa. The experimental poisson’s ratio of theprepared honeycomb is0.9551. The difference between the design value and theexperimental value is4.49%. And through the flat crush test, we know that itscompressive strength is0.424MPa, that can completely meet the requirements of airfoilaerodynamic characteristics of pressure distribution at a low speed. The last part of this paper is to get the MFC smart structure, the negative possion’sratio honeycomb and the flexible skin integrated as the smart twisted wing. Set theflexible skin elastic modulus is small, and it doesn’t produce blocking effects to thetwisted wing twisting motion. Under the ideal flexible skin situation, the maximumtwist angle of the wing can reach about8.9°, the increase of MFC groups canaccumulate the maximum twist angle of the wing. When the stick position of MFC is faraway from the fix end, an additional set of MFCs can make the maximum wing twistangle increase about2.2°. Then get intelligent twisted wing with polyethylene (PE)heat shrinkable film as its flexible skin, the maximum twist angle is3.5°, so PE filmcan meet a certain demand of wing deformation.