4D PRINTED BILAYER HELICAL STRUCTURES MECHANICAL BEHAVIORS AND SHAPE MEMORY EFFECTS

4D printing has great potential for fabricating patient-specific and stimuli responsive 3D structures for the medical sector. This paper conducts a systematic research about mechanical behavior based on 4D printing bilayer helical structure. The anisotropic characteristics of mechanical and shape memory performances induced by different infill strategies via both experimental and theoretical methods are investigated. In the proposed method, the bilayer structure is fabricated by three-dimension printing and heated in the water bath for a period of time, and then the deformed structure is obtained. The influence of printing temperature and angle on the storage modulus of shape memory materials (SMP) is explored by dynamic mechanical analyzer (DMA). The influence of environmental temperature and angle on the stress-strain curve of polylactic acid test (PLA) is explored by stretching machine. Deformation recovery tests were performed on the helical structure by pre-editing, and 3D convertible structures with programmable Poisson's ratios were fabricated to demonstrate. The effects of process parameters on the elastic modulus, storage modulus and shape memory behavior were verified.