Design And Investigation Of Dynamic Crushing Of Graded Lattice Cylindrical Shell Structure

The lattice cylindrical structure has been widely used in the area of aerospace for its lightweight and high strength.With the recent urgent demand of lightweight energy absorption device,lattice cylindrical shell structure aroused the attention of scholars as a potential energy absorbing component.So far,the investigation of static mechanical properties of lattice cylindrical structure has been well developed,but the understanding of its dynamic deformation and failure mechanism are not clear yet,and the investigation of density gradient lattice cylindrical shell structure is bland.In this paper,the mechanical properties of gradient lattice cylindrical shell and sandwich cylindrical shell under dynamic crushing is studied systematically by theoretical analysis,numerical simulation and experimental verification.The main contents is as follows:Firstly,taking full advantage of the characteristics that 3D printing can manufacture complex microstructures,an ABS triangular lattice cylindrical shell and lattice sandwich cylindrical shell are designed and manufactured.Quasi-static compression tests are conducted to get the carrying ability and energy absorption characteristics,several typical failure modes are observed.It is found that the specific energy absorption of lattice sandwich cylindrical shell are much higher than that of lattice cylindrical shell,the interaction between core and skins can efficiently improve the peak force and energy absorption of structure.Furthermore,the finite element software ABAQUS is adopted to simulate the compression progress of lattice cylindrical structure,good agreement is achieved.Secondly,based on the one-dimensional wave theory,the dynamic plateau stress prediction model of two typical lattice cylindrical shell which are membrane-dominated(triangular configuration)and bending-dominated(hexagonal configuration)is built.It is established that the theoretical prediction results agree well with the finite element simulation results.Then the influence of impact velocity and relative density on the dynamic crushing is considered,revealed the crushing deformation mechanism.Based on that,the influence of density gradient's magnitude and arrangement on the normalized plastic dissipating energy is investigated,the results show that introducing positive density gradient can enhance the energy absorption at early stage of the crushing for lattice cylindrical shell under low impact velocity.Then,taking lattice cylindrical shell as core,adding inner and outer skin to be the constrain to build the analytical model of lattice sandwich cylindrical shell.The simulation method is used to investigate the deformation modes and special energy absorption(SEA)of lattice sandwich cylindrical shell under dynamic crushing.The results show that the ratio of cell wall to skin thickness is the key factor to influence the deformation modes and SEA.By introducing density to the core of sandwich cylinder,it is found that introducing density gradient can efficiently reduce the peak crushing force of hexagonal lattice sandwich shells but have little effect on the energy absorption.Finally,a kind of negative Poisson's ratio lattice cylindrical shell model is proposed,and the quasi-static compression is conducted.The deformation modes and plateau stress of lattice cylindrical shell under different crushing velocity are investigated.Combining positive and negative Poisson's ratio,a zero Poisson's ratio(SILICOMB)lattice cylindrical shell and sandwich cylindrical shell are designed.It is found that plateau stress of SILICOMB lattice cylindrical shell is inferior to that of the hexagonal lattice cylindrical shell,the special energy absorption of SILICOMB lattice sandwich cylindrical shell is between triangular and hexagonal ones when the relative density of core is beyond 4%.