Mechanics and deformation of shape memory polymer kirigami microstructures

The assembly of three dimensional (3D) structures through compressive buckling of 2D precursors can serve as a promising and robust tool to realize different classes of advanced materials in a broad range of applications with complex geometries and a span of length scales from sub-micron to macro scales. In this study, a shape memory polymer (SMP) material was used as the precursor to form different configurations of 3D kirigami microstructures. 3D SMP structures can serve in a wide range of applications, such as biomedical and aerospace, which require a level of robustness and compliance. To this end, the mechanical response of assembled 3D buckled kirigami structures were investigated through mechanical cyclic and single loading compression at room and elevated temperatures, respectively. The experiments at room temperature were performed to examine the mechanical resilience and stability of the structures upon repeated loading. The load bearing capacity, resiliency, and stability under deformation were shown to be largely affected by their structural shape. In-situ scanning electron microscopy experiments at elevated temperatures demonstrated the outstanding shape memory behavior by full recovery to their original shape, without any structural damage or fracture. Computational modeling supports the experimental findings and contributes to the understanding of deformation and fracture of the structures.