Electrothermal shape memory behavior and recovery force of four-dimensional printed continuous carbon fiber/polylactic acid composite

Four-dimensional (4D) printing technology provides new ideas for the preparation and structural design of multifunctional shape memory composites. Excellent electrothermal shape memory behavior and high shape recovery force are urgently demanded in practical applications. Herein, a continuous carbon fiber reinforced polylactic acid shape memory composite with high strength, high shape recovery force, low-voltage response and excellent electrothermal shape memory behavior was printed using a dual nozzle 3D printer. The effects of specimen thickness, carbon fiber content, and applied voltage on the electrothermal shape memory behavior and shape recovery force were investigated. The reinforcing effect of carbon fiber on 4D printed composite materials was characterized by dynamic mechanical analysis and 3-point bending test. Under electrical thermal stimulation, the shape recovery ratio of most specimens can reach 90%. The shape recovery force of different specimens was obtained by self-designed shape recovery force test system, and the maximum shape recovery force was about 7.38 N. The results show that the introduction of continuous carbon fiber not only significantly enhances the strength of 4D printed composite, but also improves the shape recovery force. The demonstrations of an electrothermal response shape memory deployable claw-device and load-bearing lifting device manifest the potential application in self-actuated intelligent structures.