Shape Memory Polymer Composites for Aerospace

Smart materials are able to modify their physical and chemical properties in response to change coming from the external environment. Among them, the shape memory materials can be frozen in a temporary configuration upon applying external constrain and certain stimuli such as heating. Upon recovery the initial equilibrium configuration, they can release the load which has been stored as energy during deformation, and which can be used for actuation. Over last years, shape memory polymer composites (SMPCs) are the main investigated materials because they combine the structural performances of traditional laminates and the functionality of the shape memory polymers. The epoxy matrices exhibit higher shape memory performances than the thermoplastic counterparts. SMPCs are commonly used in advanced sectors such as in Aeronautics and in Aerospace. Considering the last developments in this field, the Ph.D activities has been focused on innovative SMPCs obtained by co-curing two different epoxy systems in a single press moulding step starting from commercially available materials to increase the reliability of the process and of the produced final laminates. The properties of the obtained laminates can be tailored in dependence of the amount of the SMP inserted during lamination. After proving the reliability of the adopted lab-scale manufacturing procedure, the first investigations aimed at understanding the physical mechanisms regulating the interaction between the two epoxy systems and so, dynamic mechanical analysis and differential scanning calorimetry have been carried out. Moreover, the shape memory performances were also investigated through a novel instrumented thermo-mechanical cycle, also matter of publications, based on 3-point bending configuration. The produced SMPC structures have a great ability in freezing the temporary non equilibrium configuration and are also able to recover almost the whole imposed deformation. In addition, they can be subjected to multiple thermo-mechanical cycles without incurring in irreversible damages. Another important goal of the Ph.D activities was the integration, in the developed structures, of external heating systems able to guarantee an autonomous heating and a better control of the working temperature. This is a strong achievement in that no similar studies have been found regarding this topic. Finally, considering the possibility of using the developed SMPCs for Aerospace applications, an important series of experiment have been carried out on the International Space Station thanks to the collaboration of the MaterG research group with NASA. This experimentation allowed to validate SMPCs in Space environment and for this reason contextual activities regarding the development and prototyping of grabbing systems (also topic of the European Project “Smartfan”) with and without embedded heating systems, and the modelling of a deployable solar sails either numerically either experimentally (in collaboration with ASI) were carried out.