Energy Absorption of Hybrid Lattice Structure based crash box designed for Additive manufacturing

Abstract

Lattice structures have gained immense popularity in industries like automotive, aerospace, and biomedical due to their low densities and ability to occupy design areas unattainable with dense materials. Hybrid lattice structures, designed with a specific arrangement of unit cells, exhibit enhanced mechanical characteristics like specific stiffness and energy absorption, have been developed to improve the performance of homogenous lattice structures. This thesis explores the design of a hybrid lattice structurebased automotive crash box designed for additive manufacturing. The study utilizes three lattice structures from both truss and TPMS lattice categories: Diamond, Octet, and BCC. Two unique hybrid lattice structures were designed with different number of unit cells per layer and strut thickness. A total of 12 hybrid and 3 homogenous lattice structures were studied experimentally. The force-deformation curve generated by the hybrid structures exhibits three distinct phases: characteristics of the three lattice structures. The homogenous lattice structures exhibited shear failure behavior. The deformation of the hybrid lattice structures process begins with the least stiff lattice structure within the hybrid structure with a layer-by-layer failure. The study found that HS7 exhibits the highest SEA of 12.7 KJ/Kg. Further, crash box was designed based on hybrid lattice structures. The impact response of Four crash boxes were studied using high strain rate impact simulations. Force-deformation plots showed distinct force reactions for traditional (CB1 and CB2), and lattice filled crash boxes (CB3 and CB4). CB1 having a steel shell absorbs more energy but at the cost of higher mass, CB2 made up of aluminum has higher SEA than CB1 but less EA. CB4 (PLA lattice core) has a higher initial force and slightly lower SEA than CB3. CB3 had the lowest initial force, and progressive force increases throughout deformation, therefore, achieving the highest SEA of 11.08 KJ/Kg. The specific energy absorption was in the increasing order of CB1, CB2, CB4 and CB3. The results demonstrate that lattice filled structures polymer based can be used for energy absorption purposes in various industries including automotive industry.