Dynamic Behavior and Impact Tolerance of Elastomeric Foams Subjected to Multiple Impact Conditions

Hyperelastic foams are an ideal class of impact mitigating materials in applications where more than a single impact loading event may exist. However, methods and protocols used to characterize impact tolerance in hyperelastic foams subjected to multiple impact conditions are limited and provide insufficient information about the impact load-bearing efficacy of the material. In this work, we present a comprehensive experimental approach that allows for investigating the dynamic behavior and impact tolerance of a novel elastomeric polyurea foam. The proposed approach includes conventional experimental techniques, e.g., impact force analyses, supplemented by full-field strain measurements and the evaluation of strain-dependent Poisson’s ratio of the foam as additional metrics that enable a detailed study of the evolution of the macroscopic dynamic behavior of the foam in response to multiple impacts with variable impact energies. The experimental measurements are coupled with mesoscale finite element analyses and post-deformation microstructural observations. Results obtained herein indicate the possibility of internal damage formation as the primary source of the slight decrease in impact mitigation efficacy. Specifically, the highly stretched polyurea cell walls in the foam are identified as the source of microscopic, permanent damage. Despite the significant damage developed during the multi-impact loading, the foam retains an effective level of overall impact energy mitigation capacity.