Dynamic fracture of aramid paper honeycomb subjected to impact loading

Abstract The dynamic compression behaviors of aramid paper honeycombs, i.e. samples with heights 2.10 mm, 3.10 mm, 5.14 mm, and 10.11 mm, were investigated by the split Hopkinson pressure bar devices (SHPB). The results showed abnormal size effect in the peak stress for samples with height 2.10 mm. The high speed camera was used to capture the deformation process. Two deformation modes, i.e. the in-plane shear wrinkles (characterized as larger deformation and lower strength in the stress-strain curves) and the out-of-plane wall buckling (characterized as smaller deformation and higher strength in the stress-strain curves), were distinguished from the complicated deformation processes. The abnormal size effect was resulted from the dominance of in-plane shear failure for samples 2.10 mm, rather than the out-of-plane wall buckling for other samples. Further investigations were conducted in details on the effects of cell width, wall thickness, and ends constraint condition (i.e. ends bonded with face sheets) to the deformation process based on the experiments, theoretical analyses of buckling, and Finite Element method (FEM). The transition of two deformation modes was analyzed, and the abnormal size effect would disappear for samples with larger wall thickness. It might be helpful for design purpose of honeycombs to some extent.