Shape memory behavior of 4D printed CF/PEKK high temperature composite under subsequent thermomechanical cycles

Shape memory effect (SME) in high temperature polymers (HTPs) has great significance in space for making self-deployable structures, needing high strength and stiffness during operation, signifying the necessity of exploring HTP composite with SME. This work investigates the SME of 4D printed carbon fiber/polyether ketone ketone (CF/PEKK) HTP composite under subsequent thermomechanical cycles for the first time. Scanning electron microscopy (SEM) revealed uniform distribution of CFs in developed composite, filament, and prints with seamless raster and layer deposition, confirming suitable selection of processing parameters. Prints exhibited excellent shape fixity, Rf = 90 % and 91 %, and shape recovery, Rr = 96 % and 89 % in the first and tenth cycle, respectively. A significant loss of 7 % in Rr is observed in tenth cycle. Glass transition (Tg) and degradation temperature (Td) of CF/PEKK prints are observed to be 162 °C and 568 °C, while storage modulus is found 157.69 % and 38.69 % higher than PEKK and PEEK, respectively. This study revealed an excellent SME of 4D printed CF/PEKK composite with outstanding Tg and Td, showing great potential for space applications.