Design, manufacture and evaluation of bending behaviour of composite beams embedded with SMA wires

An experimental study has been conducted to design and fabricate smart composite beams embedded with prestrained nitinol wire actuators. The developed fabrication process allowed both quasi-isotropic E-glass/epoxy and carbon/epoxy hosts to be eccentrically embedded with 10 parallel prestrained wires with a purpose-made alignment device and cured successfully in an autoclave. Smart composite beams of three different lengths were made for each type of host. Both single-cycle and multi-cycle thermomechanical bending actuations of these beams in the cantilever set-up were characterised experimentally by applying various levels of electric current to the nitinol wires. The performance characteristics showed that the present fabrication process was repeatable and reliable. While the end deflections of up to 41 mm were easily achieved from smart E-glass/epoxy beams, the limited end deflections were observed from the smart carbon/epoxy beams due primarily to our inability to insulate the nitinol wires. Moreover, it seemed necessary to overheat the prestrained wires to much higher temperatures beyond the complete reverse transformation in order to generate recovery stress. The longer beams showed greater actuation rates and took less time to reach the same level of deflection. It was found that the actuation capability derived from single-cycle actuation exercises was not suited to multi-cycling actuations and could result in premature failure of multi-cycled smart beams.

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