Determination of the Bending Stiffness of a Novel Highly Integrated Microconcentrator Design for Space Applications

A novel photovoltaic microconcentrator design for space is developed, in which the optical elements are integrated into a honeycomb and solar cells are located on a glass substrate to face the optics. The final structure is composed of two stacked sandwiches of different materials and sizes. The purpose of this study is to assess the mechanical behavior of this structure under bending loads in order to optimize the design of the microconcentrator structure to meet space specifications. Taking the influence of the thermal vibrations of the structure on the optical performance into account, the maximum length of the solar panel assembly is estimated. To do so, four-point bending tests were performed on six variations of the design. Then, an analytical and two finite-element models of the bending tests were implemented and the results were compared with the experiments. The friction between the test fixture and the samples proved to induce an overestimation of the bending stiffness by up to 34%. In the end, the bending stiffness per unit of mass and the stress distribution of the structures were assessed to determine the most interesting variations of the design. The glass should be the thinnest possible depending on the stress relative to the mission of choice for the spacecraft. The bottom honeycomb should be thick to increase the stiffness. The bending stiffness target of
$5\times 10^{6}\text{N}\cdot \text{mm}^{2}$
and the acceptance angle of 4.2
$^\circ$
limit the solar panel assembly length to 8 m.