4D printing has recently emerged as a new manufacturing paradigm by integrating shape memory materials with 3D printing technology. Distinctively, 4D printed structures exhibit dynamic shape changing capability over time in response to certain stimuli. The emerging shape memory property of 4D printed components has attracted increasing research attention due to its potential applications in soft-robotic, origami, and self-construction structures. Ensuring product durability is key to enhancing the technology diffusion of 4D printing as it significantly affects the product service life. In the current literature, durability issues in 4D printing have been largely overlooked and the relationships between external stimulus conditions and the thermo-mechanical cycle life of 4D printed parts remain unknown. To tackle this challenge, in this study, the design of experiments approach is adopted to comprehensively investigate the impacts of external stimulus conditions on the shape memory cycle life of the 4D printed thermo-responsive parts. The results suggest that increasing the operating temperature within the material-allowable temperature range would negatively affect the shape memory cycle times; meanwhile, varying the shape programming hold time also exhibits noticeable impacts on the durability of 4D printed parts. In addition, the extreme stimulus conditions with respect to the high temperature and prolonged shape programming time would worsen the shape memory cycle life.

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