3D PRINTING TO INTEGRATE ACTUATORS INTO COMPOSITES

Material based actuation with metallic fibers, for example shape memory alloys (SMA) is gaining popularity to replace the conventional bulky actuators used for shape morphing in aerospace sectors. However, Joule heating arising from electrical actuation of SMA affects the interfacial bonding between the SMA and the composite matrix and thus reduces the life span of the structure. Insulating the SMA from the composite matrix will tremendously increase the service life of these reconfigurable structures. Three-dimensional (3D) printing of functional elements during the fabrication phase of the composite structures permits the flexibility to form complex shaped reconfigurable lightweight aerospace components. Here, we present a novel technique to embed polymer encapsulated functional elements into structural composites. We use the direct-write (DW) technique to coat SMA with a polymer solution while simultaneously printing them onto carbon fiber prepreg. We develop high performance polymeric inks - polyetherimide and polycarbonate - compatible with the DW technique, the coating, as well as the composite. In addition to SMA, the technique can also be easily extended to embed various kinds of other functional fibers into composites, in any shape or form. Additionally, we also demonstrate the application of this technique to integrate SMA with polymeric structures towards actuators for robotics grippers or surgical tools. Successful demonstrators of our technique, in the form of SMA-CFRP hybrid and SMA-polymeric leaf-spring actuators are presented.