Experimental Performance Assessment of Energy Absorbing 2D Lattice Structures under Quasi-Static Compression

Introduction: Energy-absorbing lattice structures offer significant potential for lightweight and crashworthy applications because their mechanical response can be tailored through geometry. However, topology selection requires consideration of multiple performance objectives, since high energy absorption, low peak reaction force and mass efficiency may lead to different rankings of candidate configurations. 

Methods: Seven two-dimensional lattice configurations were selected to represent conventional, auxetic, anti-tetrachiral and custom designed topology families with distinct deformation mechanisms. The specimens shared the same nominal external dimensions but did not have the same relative density, because each topology resulted in a different solid volume. They were additively manufactured in PLA and subjected to repeated displacement controlled quasi-static compression tests at a constant crosshead speed of 2 mm/min; strain rate was therefore not treated as an experimental variable. Their response was assessed through force-displacement behaviour, deformation and collapse mechanisms, absorbed energy, specific energy absorption and peak reaction force. Both absolute and mass-normalized indicators were considered. 

Results: The experimental campaign revealed markedly different responses among the investigated topologies in terms of stiffness, collapse progression, energy absorption and peak force. Within the investigated set, no single topology was optimal across all considered metrics. Configurations exhibiting high absolute energy absorption did not necessarily provide the best compromise in terms of mass-specific performance and peak force mitigation. Conversely, geometries characterized by lower peak forces may offer advantages in limiting transmitted loads, although potentially at the expense of overall energy absorption. These findings demonstrate the importance of a multi-metric approach for meaningful topology selection. 

Conclusions: The study provides an experimental framework for comparing energy-absorbing 2D lattice structures according to complementary mechanical performance indicators. The results support topology selection for different design objectives and provide a basis for identifying promising configurations for subsequent dynamic investigations, numerical correlation and future lightweight applications.