Functionally graded sinusoid-based metamaterials: Towards tailoring effective mechanical properties and deformation modes with a single design parametric function

Gradual variations in the structure of metamaterials, known as functionally graded lattices, are increasingly being employed to enhance material performance across various engineering fields. Breaking symmetry and uniformity has enhanced functionality by improving mechanical properties like stiffness, energy absorption and unique deformation mechanisms. The present study introduces a novel design framework for creating a wide range of graded lattices made of curved constituent elements parameterized with sinusoids. This design approach allows the gradation of horizontal and vertical constituent elements independently. Specimens were additively manufactured to experimentally characterize the mechanical properties, deformation modes, and energy absorption under quasi-static compression tests. These experimental results were compared with nonlinear finite element models, resulting in good agreement. The graded lattices generated result in predictable deformation, smoother transitions between elastic and plastic deformation, higher strength and increased energy absorption compared to their uniform counterparts. Varying only one design parameter resulted in a 33% increase in the effective Young’s modulus, while maintaining the variation of volume fraction with < 2%. This study demonstrates the potential of this design framework to obtain a wide design space for a desired mechanical performance while controlling the directionality dependence of the properties in the two main axes. • Design of graded sine-lattices with stiffness tuned up to ten-fold using one parameter. • Characterization of the deformation modes of functionally graded sinusoidal lattices. • Graded lattices with different mechanical properties while maintaining the same relative density. • Graded lattices with a 33% increase in energy absorption compared to uniform designs.