Hatch-spacing-regulated sequential electrothermal deformation of 4D-printed continuous carbon fiber-reinforced shape memory polymer composites

Continuous carbon fiber (CCF)-reinforced shape memory polymer composites combine structural reinforcement with electrothermal actuation, but programming sequential deformation under a single electrical input remains challenging. Here, glycol-modified polyethylene terephthalate (PETG)-based polymer–composite–polymer sandwich structures were fabricated by continuous fiber additive manufacturing. Spatially varied hatch spacing was introduced as a structural design parameter to regulate fiber distribution and electrothermal deformation behavior within single composite structures. Simulations and experiments showed that decreasing hatch spacing or constituent-layer thickness accelerated electrothermal heating. Under a constant current of 0.1 A, reducing the hatch spacing from 2.6 to 1.0 mm increased the experimental average surface temperature after 100 s from 70.3 to 119.7 °C. Shape recovery tests further demonstrated that reducing hatch spacing accelerated the recovery process, with the 95% shape recovery time ( t 95 ) decreasing from 58.7 ± 2.8 s to 21.4 ± 1.8 s as hatch spacing decreased from 2.6 to 1.0 mm. Based on this hatch-spacing-dependent electrothermal response, spatially varying hatch spacing enabled sequential deformation programming within single structures. A two-tier flower-like structure unfolded sequentially from the outer petals toward the inner petals, while gradient strips exhibited programmable curling and self-closing behavior, maintaining the closed configuration after 20 programming–recovery cycles. These results demonstrate a simple strategy for programming electrothermally driven sequential deformation through continuous fiber spatial distribution design and constructing deployable and self-closing CCF-reinforced composite structures.