Morphing flat sheets to 3D curved surfaces with optimal mechanical performance

The techniques of transforming flat sheets into three-dimensional (3D) curved shapes have emerged as powerful tools to enable a broad range of applications in mechanical and biomedical engineering, robotics, architectures, and science. However, the existing approaches are intrinsically designed to create soft and stretchable structures. Therefore, morphing flat sheets towards curved and conformable geometries while achieving high mechanical strength has not been demonstrated. Here, we report an optimal cutting approach to transform plies of two-dimensional (2D) inextensible yet flexible composite laminate into 3D doubly-curved surfaces with optimized mechanical properties. Guided by a numerical model, the 2D composite plies are rationally tailored, leading to the desired 3D structures with no cut overlapped at the same position among the stacked layers. After consolidation of the plies, the shearing force among the plies can significantly eliminate the effect of the cuts that normally will weaken the mechanical strength of the structures. Our approach opens a fundamentally new paradigm to conform complex shapes of arbitrary curvatures while offering control over the local architecture for lightweight, high mechanical strength.