Hybrid Composites for Morphing Applications


This work is directed towards realizing large scale shape changes of wing like structures. It is relevant to discuss the work carried out in this area so far. AMR BAZ (ref l) details the work in which SMA is embedded in sleeves located at the neutral planes and arranged parallel to the longitudinal axis of the composite beam. Here emphasis is placed on describing quasi-static theory of shape control and implementation of this theory to composites incorporated with SMA. Emphasis has been placed on full utilization of shape memory effect without compromising on structural stiffness of the composite beam. Koryo Miura et a1 (ref.2) explain about adaptive structures and their use in aerospace applications. Here a variable geometry (VG) truss concept is presented. Comparison is made between tetrahedral and octahedral truss elements. Since octahedral is richer in symmetry, it is considered to be adequate for adaptive structures. DC motor is used as an actuator. It is shown that VG truss is the basic form of adaptive structures. The basic formulations for its geometrical as well as vibrational properties are established. Some applications such as second generation manipulator arm, support architecture for a space station and others are discussed here. Deepak.S. Ramrakhyani et a1 (ref.3) explains about the use of compliant cellular truss where tendons are used as active elements. This tendon actuated elements can be used for local or global shape changes. Here an octahedral unit cell is developed for bending deformations and compliant joints are made of cylindrical elements of superelastic shape memory alloys. Several concepts of morphing skin were also presented. Tendon actuators are presently under development. The tendons could be actuated locally or combined from a remote location such as the root of the wing. Since we are looking for large deflection of thin beams we have deliberately embedded the SMA wires off the neutral axis of the beam. In the literatures there is hardly any material that deals with this type of an approach. In this the effect of embedding the thermal SMA wires off the neutral plane of thin beams was studied. These wires were prestrained and embedded off the neutral axis to produce high amount of recovery forces when electrically energized. Superelastic SMA (SESMA) wires were used on the other side of the beam so as to increase the spring back effect of the beam when de-energized. Thus we were able to obtain large deflection together with faster return back to original position when de-energized

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