High strain rate testing and modeling of 3D-printed polymeric cellular structures

In the past few years, growing attention has been given to crashworthiness studies of 3D-printed lattice and cellular structures due to their excellent energy-absorbing capabilities and design freedom. The high strain rate behavior of these components has not been fully comprehended and their use is thus still limited. This paper investigates the high strain rate behavior of 3D-printed polymeric cellular structures, varying cell topology, material, density, and launching speed. The specimens are compared by quasi-static and dynamic compression tests, with strain rates varying from 0.01 s-1 to 3000 s-1. A Taylor test is employed to achieve launching speeds up to 200 m/s, which are rarely investigated for such structures. The wide range of strain rates results in notable changes in the collapse mechanisms of the structures and outstanding enhancements in specific energy absorbed. A new specific energy absorption evaluator is developed to account for the different behaviors of the quasi-static and high strain rate cases. Different results are obtained with short carbon fiber reinforced and unreinforced polyamides, while the cell topology is found to influence the failure behavior. The unreinforced material has a greater strain rate sensitivity but shows higher fracturing and catastrophic failure, while the reinforced material behaves more stably. Lastly, a simple finite element model with reduced inputs is developed to reproduce the deformation and the specific energy absorption of the structures. The model is intended to promote the use of simpler yet accurate models in large crashworthiness studies, where 3D-printed polymeric structures can be used.