Investigating the effect of thermomechanical cycles on shape memory effect of four-dimensional printed glass fiber/polyether ketone ketone composite

Abstract

Assessing the shape memory effect (SME) under repetitive thermomechanical cycles is crucial for designing structures undergoing subsequent fold and deployment during functioning, such as morphing structures and soft grippers. Four dimensional (4D) printing is a revolutionizing manufacturing technology, offering dynamic feature into three dimensional (3D) printed part. This work presents the first study on 4D printing and SME assessment of glass fiber (GF)/polyether ketone ketone (PEKK) composite for morphing structures and grippers in aerospace applications. GF/PEKK composite is developed using blending, and then filament is extruded for 3D printing. Annealing is performed on the 3D printed parts and evaluated using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and SME under subsequent cycles. The SEM analysis demonstrated the uniform distribution of GFs into PEKK with good interfacial bonds, indicating the appropriate selection of the process parameters. The composite depicted remarkable shape fixity (R<inf>f</inf>) and shape recovery (R<inf>r</inf>) of 91.07% and 96.08%, respectively, in first cycle. However, in tenth cycle, R<inf>r</inf> is found to be decreased to 86.30%, a reduction of 9.78% is observed. Key findings of this research are the excellent storage modulus of 3150 MPa, which is 82.93% higher than PEKK. Thermal studies revealed very high glass transition temperature (T<inf>g</inf>) of 175°C and thermal degradation temperature (T<inf>d</inf>) of 561.36°C, which is higher than PEKK (T<inf>g</inf> = 161°C and T<inf>d</inf> = 548°C), demonstrating excellent thermal performance and showing potential for high-temperature shape memory applications. Highlights: Composite showed excellent shape fixity (91.07%) and shape recovery (96.08%). Quick shape recovery in 20 s showed potential for a swift actuator. Storage modulus of 3150 MPa is observed for the composite. Composite has a glass transition temperature of 175°C. Composite exhibited a high thermal degradation temperature of 561.36°C. © 2025 Society of Plastics Engineers.