Evaluating Energy Absorption Performance of Filled Lattice Structures

Filling the voids of lattice structures with a second material is known to increase energy absorption capacity, but the practical performance benefit is hard to quantify when the maximum stress also rises. In this article, we introduce a new metric, the energy absorption performance index (EAPI), that combines energy absorption, mass, and maximum stress into a single scalar value, enabling us to assess the true utility of filled lattices relative to single‐material lattices. The principles that define EAPI are first established by analyzing a dataset of over 170 absorber compression tests, which show that it captures the most relevant aspects of design, making it suitable for evaluating new design concepts such as filled lattices. A finite element study is then performed to understand which filled lattice architecture/material combinations lead to improved performance according to the EAPI metric. Three representative lattice unit cells (octet, rhombic dodecahedron, and body‐centered‐cubic with z orientation) and three representative filler materials (low‐density polyethylene, silicone rubber, polystyrene foam) are considered in the analysis. The results show that fillers typically reduce performance, and that only marginal improvements are possible in lattices prone to buckling, combined with high‐performance (high EAPI) fillers. The same trends are observed when the EAPI metric is applied to analyze prior experimental studies comparing filled and empty energy‐absorbing structures. The results of this work have significant implications for the design selection of energy absorbers and for future research aimed at achieving improved energy absorption performance.