Active hybrid composites are gaining significance in various industrial and medical applications. These composites can include the integration of shape memory alloy (SMA) wires and fibre-reinforced plastics at material level and have the ability to undergo large deformations while activated. Typical applications are aerodynamic components such as car spoilers or wing profiles of an aircraft. Most applications often follow a partially integrated or modular shape memory alloy hybrid composite (SMAHC) design. In this paper, we pursue the approach of a fully integrated construction of an SMAHC. Therefore, we introduce two different designs of flexible interlayer of a 4D printed SMAHC by using the 3D stereolithography process. Achieving direct integration of SMA’s into plastic matrices requires the matrix material to possess adequate flexibility, as the SMA's thermal phase transformation process can accommodate elongation of up to 8%. Moreover, it is imperative to ensure that the process temperatures of the chosen manufacturing method remain below the austenite start temperature (As) to prevent inadvertent activation of the SMA during fabrication.

Morphing shape memory alloy hybrid composites (SMAHC) offer a great potential for various engineering applications due to their lightweight properties and their ability to undergo significant deformations. They fundamentally consist of two primary components: a stiff substrate and a shape memory alloy (SMA) layer, enabling external two-way shape memory capability. During actuation the metallic SMA undergoes a contraction of several percent when subjected to electric current. As the SMA contracts, the substrate retains its original length, causing a bending movement in the composite. A third component to be mentioned is the interlayer, positioned between the rigid substrate and the SMA layer, opens up a greater design flexibility. By adjusting the distance between these two components fine-tuning of the relationship between deflection and bending moment in response to an external load can be achieved. (compare Fig. 1).