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An experimental investigation of the impact of sand slugs against monolithic and sandwich beams

Tobias Uth (University of Cambridge), Vikram Deshpande (University of Cambridge)

Dynamic Behavior of Materials

Tue 2:40 - 4:00

Salomon 101

Buried landmines load structures through the combined effects of soil ejecta and an air blast. This complex loading impedes a complete understanding of the event. Therefore, this study focused solely on the interaction of soil ejecta and structures by decoupling it from the air blast. Well-characterised cylindrical sand slugs were impacted against sandwich and monolithic beams. High-speed photography was used to measure the velocity of the sand slug and the deformation of the beam. Seven different beam designs were tested in order to investigate the effect of core height and core strength on the deformation response. All beams were fully clamped and had identical width, length as well as areal mass. Impact tests were conducted with both, dry and water-saturated, sand slugs at an impact velocity of 93 m/s. The sandwich beam design with the thickest and strongest core obtained the best performance (ranked according to maximum back-face deflection). Additional impact tests demonstrated that the “strongest” sandwich beam outperforms the monolithic beam over a range of impact velocities. Compared to the monolithic beam the “strongest” beam exhibited about 6 and 4 times less deflection for dry and water-saturated sand, respectively. The superior performance of sandwich beams with thick and strong cores can be explained by the “sandwich effect”, whereby the height and the strength of the core give the beam a higher bending strength. In addition, we demonstrate experimentally that the sand slugs are well approximated by an impact foam cylinder – this experiment is considerably simpler to conduct compared to the sand slug experiments and thus proposed as a substitute to simulate dynamic sand loading in a laboratory setting.