Multistable shape-adaptive metamaterial with tailored material composition and geometry

Metamaterials exhibit distinctive properties that do not exist in natural materials. These properties result from the material’s structure rather than its composition. Shape-adaptive metamaterials are engineered with structural components that can change shape when triggered by external inputs, such as temperature, pressure, or electric fields. These materials have applications in adaptive structures in robotics, aerospace, automotive engineering, and deployable structures. However, in most applications, a continuous energy source is required to maintain a desired shape. To address this challenge, a new self-locking metamaterial employing the concept of multistability has been developed, which exhibits both translational and bending motion. These metamaterials consist of an arrangement of two different types of bistable unit cells: straight and inclined. The straight unit cells are responsible for translational behaviour, while the inclined unit cells contribute to the bending behaviour of the lattice. Each unit cell is made of four bistable anisotropic composite laminates. Composite laminate exhibits bistability due to induced residual stress generated from cool down from elevated curing temperature to room temperature. To analyse the metamaterial, a finite element model has been developed for both unit cells and lattices. Upon the application of a load, the straight stable configuration snaps into the curved stable configuration. An extensive parametric analysis has been conducted to observe the effect of different inclination angles of the unit cells on the bending behaviour of the lattice. It is observed that the maximum upward deflection of 0.43 m (along the Y-axis) for a 45° inclination angle of the laminate in the inclined unit cell. This bending mechanism can be utilised in applications such as aircraft flaps, grippers, and bascule bridges.