Active Reduction of Dynamic Fold Propagation in Deployable Shell Structures

Ultrathin composite shell structures are capable of self-deployment by releasing stored strain energy accumulated in their elastic folds during stowage. However, uncontrolled deployment is susceptible to irregular motion, self-contact, or structural damage. To ensure a reliable unfolding sequence, this paper investigates the active reduction of an elastically propagating fold in a freely deploying thin-shell composite structure. A Macro Fiber Composite (MFC) piezoelectric actuator is bonded to a cantilevered composite tape spring near the fixed root. Through voltage-induced deformations, the MFC alters the transverse shell curvature to inhibit the motion of the propagating fold. The actuation effects on deployment are investigated both experimentally and with explicit finite element analysis. The two approaches characterize the unactuated, statically actuated, and dynamically actuated deployments for the composite tape spring with a single localized opposite-sense fold. Negative static actuation prolongs unfolding, while positive static and dynamic actuation lower the deployment duration in addition to attenuating the fold propagation dynamics.