A Sensitivity Analysis of Geometric Parameters of 4D-Printed Bidirectional Shape-Memory Composite in Architectural Façade Design

Abstract

The 4D-printable two-way shape memory effect (TWSME) is not well known to building engineering and architecture. To better understand the thermo-mechanical complexity of TWSME in building skin design, this paper investigates the parametric uncertainty in basic deformation of a rectangular façade surface module. To this end, a 4D-printed TWSME composite was prototyped by 3D-printing shape memory polymer (SMP, digital elastomers DM9850 and 9885) design with shape memory alloy (SMA) wires (Ni 55.5%-Ti 44.5%wt.) inserted. A simulation-based global sensitivity analysis was conducted on the maximum displacement and force of the composite through the homogenized 1D approximation of bending and material property change in four different phases. It was identified that the simplified simulation well predicted the actual maximum reversible displacement of ~3.5 mm with a sectional area ratio of SMP to SMA of ~105 between 30°C and 65°C. Our findings indicate that sectional geometry of the bending part (width and height in the rectangle) and the intensity of the SMA pre-strain determined by a degree of fiber bending are the most critical factors to predict the maximum displacement and recovery force of TWSME. The potential building application of thermo-responsive phenomena contributes to extending smart material use in architecture and knowledge in making design decisions in self-shaping climate-adaptive building.