Damage behavior and energy absorption characteristics of foamed concrete under dynamic load

It is important to understand the damage and energy absorption of porous materials under dynamic load. As a typical lightweight porous material, foamed concrete has attracted extensive attention in recent years. The damage behavior of foamed concrete with densities of 300 kg/m³, 450 kg/m³ and 700 kg/m³ at a strain-rate range from 60 s⁻¹ to 250 s⁻¹ are quantitatively described by fractal analysis of the fragment morphology of the specimens based on split Hopkinson pressure bar (SHPB) tests. By calculating the energy generated by the action of the stress wave, the energy absorption characteristics are discussed and analyzed. The results show that the fractal dimension increases as a quadratic function with the increase of strain-rate and exhibits a transition behavior at a strain-rate of 140 s⁻¹. The energy absorption process is characterized by elastic deformation stage, crushing stage and post-failure stage. The energy absorption ratio (i.e. the ratio between the absorbed energy and the incident energy) increases with the increase of strain-rate and the maximum energy absorption ratios of foamed concrete with three different densities are 15.1 %, 18.4 % and 25.4 %, respectively. The damage sensitivity of energy absorption (DS^e) is defined to describe the relationship between energy absorption characteristics and fractal dimension, which links the dynamically-imposed energy, overall damage and fragmentation distribution. Finally, the numerical simulation based on finite element method is conducted to reproduce the dynamic damage process and further reveals the energy absorption characteristics of foamed concrete.