Low-velocity impact of castor oil-based rigid polyurethane foams: Experiments, microstructure effects and constitutive modelling

Rigid polyurethane foams (RPUFs) are widely used in impact protection applications due to their tunable mechanical properties. Recently, RPUFs derived from bio-based sources such as castor oil have been investigated as a greener and more sustainable alternative to replace fossil-based polyurethane foams. It is thus important to understand the mechanical response of these materials to low-velocity impact (LVI), which still needs to be explored. This study aims to fill this gap by evaluating the performance of three types of RPUFs developed from commercially available castor oil-based resins. Drop weight impact tests at different impact energies were performed to investigate the LVI characteristics of the foams. Furthermore, an extensive micro-computed tomography investigation was carried out to improve the understanding of the microstructure of RPUFs and how the composition of these porous materials affected the foam architecture and the macroscopic mechanical response. Finally, a constitutive relationship is proposed to describe and predict the materials’ response at different impact energies.