Simultaneous FDM 4D Printing and Magnetizing of Iron-Filled Polylactic Acid Polymers

4D printing magnetic structures with excellent strength activated with a low level of magnetic field are always desired but challenging. This work studies the influence of simultaneous magnetization on the magnetomechanical performance of 4D-printed active polymers. The main aim is to magnetise magnetic iron polylactic acid (PLA) material during 4D printing via fused deposition modelling (FDM) process. During the printing process, the magnetization of samples is performed in various magnetic field states. Specimens are printed in three states with two magnets around the printing area, magnets under the printing area, and without magnets, at three angles of 0, 45, and 90◦ to the applied magnetic field. Vibrating sample magnetometer (VSM), mechanical tests, and scanning electron microscope (SEM) are used to investigate the effects of the applied magnetic field on the magnetization with different printing conditions, mechanical properties of different printing angles, and the microstructure of printed samples. Results show that printed samples on the edge of the magnet are saturated in a higher specific magnetization compared to the printed samples with magnets around and without a magnetic field. The specific magnetization in the magnetic field in the direction of the sample deposition increases by 63.46% by applying a magnetic field. The strength increases 21.4% when a magnetic field is present, and the sample is printed at 0◦ angle along the tension direction. The printed sample has better mechanical properties when two magnets are used around the printing region rather than one under it, which is independent of the impact of the printing angle. Finally, the optimal printing mode for obtaining the appropriate magnetic and mechanical characteristics is 4D printing with magnets under the printing bed at 0◦ angle along the tension direction.