4D printing of lattice structures to test their behavior by repetitive shape processing cycles

Abstract

This study thoroughly investigated the shape memory effects of 4D printed lattice structures influenced by repetitive shape processing cycles and materials variability. The structures were fabricated by an amorphous and semicrystalline type shape memory material (SMP) and subjected to time-temperature-based thermomechanical memory cycles. Shape programming and recovery characteristics for 4D printing were done inside an environmental chamber at a loading rate of 2 mm. min−1. The shape memory effects driven by SMP’s viscoelastic behavior and performance factors were studied by stress-free strain recovery experiments upon the interaction of thermal stimuli. The stress-free strain recovery analysis expressed, that the influence of repetitive cycles was exceptional and significant for both materials. Extensive investigation on shape memory reactive strain components (i.e., programming strain, residual strain, and thermal strain) reflected, with the increasing number of cycles, the shape recovery ratios of the first to fourth cycles increased from 82 → 100% of amorphous and 79 → 95% of semicrystalline SMP and then tend to stable thereafter. Contrarily, the shape fixity ratios of semicrystalline structures have shown a decreased tendency during the consecutive cycles from 100 → 80%. The successful execution of data-oriented shape processing cycles enhanced the potential of SMP-based lattice structures for their monotonous applications as intelligent devices. The time and temperature-dependent shape memory characteristics of repetitive cycles presented in this study are advantageous to model the viscoelastic behavior of such artful structures.