4D printing of heat‐stimulated shape memory polymer composite for high‐temperature smart structures/actuators applications

Abstract High temperature shape memory polymers (HT‐SMPs) have great utilization in self‐deployable hinges/morphing structures for space/aerospace, and high‐temperature sensors/actuators for electronics. However, HT‐SMPs have many drawbacks, such as low stiffness, strength, thermal stability, and dynamic mechanical properties. This work aims at improving these properties of highly utilized space grade HT‐SMP, PEKK (polyether ketone ketone), by reinforcing it with low‐cost carbon fibers (CFs), and developing its composite via additive manufacturing. The additively manufactured CF/PEKK composites are annealed at 200 °C (CF/PEKK‐A200) and 250 °C (CF/PEKK‐A250), and for the first time, investigated for shape memory effect (SME). The shape fixity and the shape recovery of the CF/PEKK‐UNA (un‐annealed), CF/PEKK‐A200, and CF/PEKK‐A250 are noted to be 95.97%, 88.95%, and 86.40%, and 88.70%, 92.70%, and 95.19%, respectively with a significant weight saving potential of ⁓21%. Dispersion of CFs in PEKK and suitability of processing parameters (blending, extrusion, and 3D printing) are confirmed through scanning electron microscopy (SEM). Thermal degradation temperature () of the printed CF/PEKK composite (⁓568 °C) is found to be ⁓3.5% higher than PEKK (⁓549 °C). CF/PEKK‐A250 exhibited the highest storage modulus (4438.23 MPa), ~158% higher than PEKK (1722.3 MPa), while CF/PEKK‐A200 demonstrated the highest tensile modulus (10.9 GPa), which is 138.5% higher than PEKK (4.57 GPa) and 312.88% higher than CF/PEKK‐UNA (2.64 GPa). Moreover, CF/PEKK‐A200 exhibited 237.46%, 138.51%, 127.08%, 61.48%, 32.93%, and 50.35% higher tensile modulus than PEEK, PEKK, PEK, CF/PEK, CF/PEEK, and CF/PEKK composites, respectively, showing great potential to replace them. Highlights Printed CF/PEKK composites are investigated for shape memory behavior. The printed composites exhibited outstanding shape memory properties. Printed‐A200 exhibited 138.51% enhanced tensile modulus than pure PEKK. Also, the printed‐A200 showed 313% enhanced modulus than printed‐UNA. (568 °C) of the printed composites is found ⁓4% greater than pure PEKK.