Lattices structures for energy absorption: modelling and experimental study

The present study focuses on metamaterials with lattice microstructure able to absorb energy thanks to different dissipation mechanisms which can be reconducted to nonlinear constitutive effects (i.e. damage) and to nonlinear geometric phenomena. The activation of one or more dissipation mechanisms depends on the cell geometry and arrangement, on the material mechanical properties and on the rate of the load applied. For the first class of materials, numerical modeling is performed using a continuous-discontinuous framework based on an isotropic damage model. Crack initiation and propagation are modeled through the Advanced Augmented Finite Element Method (AA-FEM) [1], which employs an Inter- PHase (IPH) element [2] to represent weak discontinuities embedded within the finite elements. This approach enables the simulation of progressive damage localization and fracture evolution without resorting to remeshing or external cohesive laws, providing further insight into the interplay between geometry, material behavior, and energy dissipation mechanisms. The second class of materials adopts a geometrically nonlinear two-dimensional beam formulation, originally developed for Euler–Bernoulli beams and subsequently extended to include transverse shear effects [3]. The formulation relies on an integrated form of the equilibrium equations, coupled with kinematic relations and generalized constitutive laws, resulting in a system of three differential equations discretized using a finite-difference scheme. Numerical simulations are experimentally validated using additively manufactured specimens subjected to quasi-static compression tests. In both numerical and experimental analyses, the energy absorption performance is evaluated in terms of total energy absorption, mean crushing force, specific energy absorption, and crush force efficiency.