DIMENSIONAL INTEGRITY OF 4D PRINTED PARTS: A MULTI-CYCLE ANALYSIS FOR QUALITY ASSURANCE

4D printing is a promising additive manufacturing technology due to its capability to prolong service life and enhance the life cycle performance of manufactured structures. This study analyzes the dimensional integrity of 4D printed parts along several programming and recovery cycles; specifically, this investigation comprises a comparative study to characterize the dimensional variations along the length, width, and height, where the effects of different stimulus conditions, such as temperature and time, are also investigated. An in-depth analysis using the design of experiments technique was also performed to investigate further the impact of different factors on the cyclical dimensional integrity. The results suggest that temperature is a critical factor leading to material-dependent changes in the length and width, with the highest temperatures leading to thermal expansion since the initial programming and recovery cycle. Holding time changes were found to have a minor impact on the dimensions, while variations in deformation angle did not affect the results significantly. The outcome also suggests that mechanical loading and constant exposure to moisture could degrade the polymer, creating stress-induced mechanical fatigue or swelling changes, which consequently affects the samples' integrity after repeated exposure.