Fundamental characteristics of self-deployable convex shells using shape memory polymer

This study proposes a concept for self-deployable shell structures made of connected shape memory polymer (SMP) shells, which are configured to a convex shape. In this research, the convex SMP shell is deformed from a flat configuration to convex one by heating it. The concept aims to realize deployment without impact to the structure in the course of deployment by applying thermal control, and to offer higher stiffness of the deployed structure due to the convex configuration of the shells. In addition, the shape recovery process of the SMP convex shell realizes self-deployable and highly stable deployment capabilities because the shape recovery of SMP utilizes material response to recover the memorized convex shape rather than the release of an elastic hinge. Experiments were performed for two-dimensional deployable structures with SMP convex shells to examine the fundamental deployment characteristics of the proposed concept. The shape recovery process of the shell from the given stowed shape to the flat state was shown to be very stable, and the experimental results indicated that the mechanical properties of the tape connecting each convex shell is significant in obtaining demanded deployed states. The deployment characteristics observed in the experiments demonstrated the achievement of complete deployment and the gradual decrease in the deployment speed, implying that low-impact deployment can be realized by this concept. Moreover, the bending stiffness after deployment increased due to the shape recovery of the convex shape. The design flexibility of the convex shell was also considered by introducing another layer to vary the deployment process. All these fundamental characteristics demonstrate the potential of the proposed concept for the self-deployment of the next generation light-weight space structures.