Challenges in Transforming Brittle to Flexible Structures

Thermoelectric Generators (TEG) are typically rigid. The devices are made of several unit cells that comprise of two brittle elements each. Each element is known as a leg and is either positive or negative. The brittle nature of the legs makes the unit cells inflexible. A need exists to develop flexible TEGs for use on non-planar waste heat emitting sources. Unit cell geometry and materials affect the rigid behavior of a unit cell. The approach used in this study towards achieving TEG flexibility is to manipulate the unit cell’s geometry that allows deflection without collapsing. Two models were developed to study the extent of the unit cells’ flexibility. A successful model would allow deflection without fail when both compressive and shear loads were applied to the unit cell structure. Further, it would also maintain a parallel relationship between the top and bottom plates of the unit cell. Two modifications were made to the original unit cell structure by applying conducting polymer at the plate/element interface; and introducing diagonal elements. The first model was an indeterminate truss that used a symmetrical element design approach. The model maintained parallel relationship of the top and bottom plates of the unit cell and its diagonal absorbed loads and allowed minimal deflection of <0.01 of the diagonal member length. The second model was a determinate truss that used asymmetric diagonal element design approach. The determinate results produced better deflection results than the indeterminate model. The top and bottom plate parallel relationship was maintained, and the diagonal member absorbed both shear and compressive loads providing slightly greater deflection. A further analysis suggests a mechanism design to achieve higher deflection. The paper will discuss the first two models. In conclusion, the paper points out how engineering education could benefit from exposure and participation in such a design process even though students were not involved in this study originally.