The authors proposed a lightweight, shape-controllable actuator structure consists of shape memory alloy (SMA) honeycomb sandwiched by carbon fiber reinforced plastics (CFRP) skins. Combined with a monitoring system using fiber Bragg grating (FBG) sensors, Deformation of the structure is self-monitored in real-time. The deformation of the whole structures is caused by the recovering force of SMA when heated to its phase-transition temperature. The SMA honeycomb core is made of thin SMA foils with the thickness of 50 μm, which is extremely lightweight while capable to generate high recovery force. The structure is shape-controllable by temperature, and capable to perform a two-way actuation owing to the change in the balance between the stiffness of CFRP skins and the recovery force of the SMA core. In order to monitor the deformation, local strains at different locations on the skin are measured by FBG sensors, which transform strain and temperature to shift of optical Bragg wavelength. In detail, six FBG Sensors in a single optical fiber are assigned as either strain sensors or temperature sensors, set in pairs at three desired locations. From outputs of these sensors, local strain and temperature can be measured separately. Thus, it is possible to monitor the deformation in real-time with a single system. In the experiments, the actuator structure, which is 180 mm in length, 13 mm in width, and 16 mm in thickness, had its left end fixed, while its right end had a vertical displacement over 6mm By heating from 300 K to 363 K. The FBG sensors successfully captured local strains at the left end, right end, and the center of the upper surface of the upper skin. These values were qualitatively consistent with the result of a finite element analysis. The proposed smart structure owns three merits as an actuator: lightweight, shape-controllable, and capable of real-time shape-monitoring.
