Dynamic Response And Multiobjective Optimization Of Graded Foam Cored Sandwich Cylinder Under Internal Blast Loading

Foam materials are a kind of new engineering material with physical function and structure.Due to the unique microstructure characteristics,the compressive stress-strain curve contains a long stress platform,which shows excellent energy absorption and impact resistance.The foam materials have been widely used in energy absorption and buffer components.The graded materials,a new kind of composite materials,not only have the excellent performance of the foams,but also have design ability.Graded foams perform improved energy absorption and impact resistance by changing the density distribution of foams.Foams filled sandwich structures show a light weight,high strength,fine stiffness,excellent energy absorption,and other good mechanical properties.Graded foams cored sandwich structures can effectively play the advantages of graded foams and sandwich structures,which improve the anti-blast performance of the structures by enhancing the design of the structure and further reducing the structure weight.In this paper,dynamic response and multi-objective optimization of the foams filled sandwich cylinders under internal blast loading are investigated.The research results can provide technical support for the design and optimization of new lightweight portable explosion-proof containers.Based on the Voronoi algorithm,the finite element models of foams are established,and the crushing process of the foams is simulated and analyzed under blast loading.Based on the R-PP-L model,the governing equations of homogeneous foams subjected to blast loading are established in combination with the mass conservation and the momentum conservation.The collapse processes of graded foams are numerically simulated.When the gradient is positive,the soft layer is placed at the proximal end.The densification wave occurs at the proximal end and then gradually propagates to the distal end.When the gradient is negative,the crushing waves in the two layers propagate toward the fixed side at the same time.According to the deformation process,the governing equations of graded foams subjected to blast loading are established.According to the experimental and simulation results,the deformation process of sandwich cylinders is simplified and decoupled into three stages,namely,the interaction between the blast loading and the inner face-sheet,the core densification,and the outer face-sheet deforming.Based on the governing equations of homogeneous and graded foams,the theoretical analysis model of graded foams filled sandwich cylinders is established by combining stress analysis of sandwich cylinders.The sandwich cylinder with high energy absorption and low deflection is a good choice to maximize the blast resistance at a given mass subjected to internal blast loading.The energy absorption and the maximum deflection are two conflicting objectives to evaluate blast resistance for design parameters.It is found that the anti-blast performance of the foams filled sandwich cylinders is better than that of single-layer containers.When the explosive charge is 2 kg,the maximum deflection and the energy absorption of the foams filled sandwich cylinders are reduced by 9.0% and improved by 269.5%,respectively.The energy absorption and maximum deflection are taken as the objective optimization functions.The multi-objective optimization mathematical models of the foams filled sandwich cylinders are established.The response surfaces are constructed by the agent model method.The genetic algorithm is used to obtain the Pareto frontier of the multi-objective optimization.The results show that the energy absorption of the explosion-proof containers with optimized core gradient and optimized face-sheet thickness improves 75.4% and 45.0%,respectively.The energy absorption improves 171.1% when the core gradient and face-sheet thicknesses are optimized at the same time.