MANUFACTURING OF ADAPTIVE GRAPHITE-EPOXY STRUCTURES WITH EMBEDDED NITINOL WIRES

Shape memory allay (SMA) composites are a class of smart materials in which embedded nitinol wires are used as actuators. Previous research in SMA composites has been limited to wires using one-way shape memory behavior. The objective of this paper is to assess the feasibility of using two-way shape memory (TWSM) training of nitinol, a nickel-titan ium SMA, wires for their use as embedded actuators in SMA composites a nd to investigate the effects of processing conditions on SMA composit e quality and actuation ability. Training of the TWSM behavior in niti nol was investigated for a range of initial strains and training cycle s. In each case, over 50% of the initial strain can be recovered after training and trained response is generally stable after about 30 trai ning cycles. SMA composite specimens were manufactured using either ho t press or autoclave methods and several different types of cure cycle s. Voids were found to congregate near the embedded wire surface and c an typically be as high as 10% in these regions. Using a staged-cure c ycle, the average void content was reduced to 1.3-1.5%. The effect of the composite cure cycle was found to have no significant effect on tr ained nitinol wire behavior. Finally, the structural behavior of an SM A composite beam was investigated by actuating wires through electrica l resistance heating. The tip deflection of a cantilevered beam was fo und to be primarily composed of SMA transformational effects, however, some localized heating was evident.