Free-form optimization of sandwich structures for controlling thermal displacement

Considering the different thermal expansion coefficients of skins and cores, sandwich structures whose design optimization is performed have the potential for application in thermal actuators. In the present work, we propose a free-form optimization method for the design optimization of sandwich structures composed of two thermoelastic materials (A and B) for controlling their thermal displacements. We use the square displacements error norm between the thermal displacement and target displacement at the designated boundary as the objective function, and minimize it by optimizing the interface and the surface shapes of the sandwich structures under thermal load. We derive the shape gradient function by using the material derivative method and apply it to the free-form optimization method for determining the optimal shape. Two volume constraints, the total volume and volume of material A, are considered in the problem formulation. The numerical results show that the thermal deformation of the optimal sandwich structure can be well identified; this is helpful for applying sandwich structures in thermal actuators.