Multilayer and multifield analysis of origami deployable structures

The research focuses on design of origami deployable structures for space applications. The aim is to acquire new and in-depth knowledge on modeling deployable structures with simple origami folding patterns to enhance the reliability of subsystem design requiring the use of such structures. Mastery of the subject will also enable the analysis of the compatibility of flexible thin structures with electronic components such as flexible rigid PCBs, solar cells, or antennas. The most used method of modelling for the analysis of flexible structures is based on bar-and-hinge models (reduced degree-of-freedom models) which, although accurately describe the macroscopic behavior, are unable to capture local behavior at critical points such as folds and interface points with bonded rigid-flexible elements. Consequently, a refined analysis of the system is carried out by integrating the finite element Carrera Unified Formulation (CUF) in the bar-and-hinge model, which allows to reduce the number of degrees of freedom with respect to classical Finite Element Method (FEM). Such formulation is necessary for two main reasons. Firstly, integrating this formulation with classical reduced degrees of freedom models will allow analyzing the local behavior of the deployable structure while still keeping computational costs low. Secondly, the CUF model is well suited for modeling thin multilayer structures, consisting of layers of very different materials, thanks to the possibility of selecting an arbitrary approximation order along the thickness that is independent of the order of the model adopted in the plane. Such a powerful tool will also allow analyzing the behavior at the interface between distinct layers subjected to both mechanical and coupled thermomechanical stresses, a critical condition in space applications. The final step of the modeling involves research on controlled deployment methods, deepened to ensure greater system reliability and morphing capabilities. The developed models will be experimentally validated through test campaigns aimed at verifying that the stress and strain states resulting from the analyses are comparable to those evaluated in experimental tests. These tests will include, among others, deployment tests of structures with origami patterns or classic folding patterns to evaluate opening stresses and cyclic thermal fatigue tests to evaluate thermomechanical stresses at the interface between distinct layers. The comparison will provide the numerical model with additional robustness and make it a tool capable of predicting complex behaviors otherwise investigable only through experimental tests.