Shape memory polymer composite device with embedded heater for one way soft actuation

A novel architecture of shape memory polymer composite (SMPC) sandwich actuator has been designed and prototyped. Epoxy foams obtained by a solid-state process without the use of foaming agent were placed in the center of the device. High performance Carbon Fiber Reinforced (CFR) prepreg was used for the external skins and at the edges of the device to increase the stiffness of the actuator. Thermal activation was obtained through a flexible heater powered with a maximum tension of 26 V. Moreover, SM thin layer (interlayer) obtained by the same resin used for the foam were deposited to insulate the heater from the CFR plies and to allow adhesion of the foam to the bottom CFR skin. Two more actuators in the forms of a 2-ply laminate and of a 2-ply sandwich with two epoxy foams placed in the center of the device were also manufactured for comparison. All the actuators were manufactured by a hot press moulding process. At the end of manufacturing, optical images revealed the soundness of the manufacturing procedure. Memory, constrained recovery and free recovery tests in three point bending configuration were performed to evaluate the shape memory performances and the actuation loads. The developed actuator exhibited the highest value of shape fixity (97%) and high shape recovery ratio (95%) with also interesting actuation load of about 2.3 N.