Research On The Response&Damage Of Low Velocity Impact Of Pre-stressed Composite Sandwich Structures

A finite element software MSC.Dytran is employed to establish the finite element models(FEM)of low-velocity impact for the pre-stressed composite sandwich structures.The response and impacting damage of the pre-stressed composite sandwich structures under low-velocity impact are investigated.The research work of this paper includes the following three aspects.Firstly,a FEM is established for the prestressed composite pyramidal lattice structures under low-velocity impact.The influences of impact velocity,impactor mass and face-sheet thickness on the impact response of the pre-stressed structures are investigated,respectively.The results show that the peak contact force increases with increasing the impact velocity or the thickness of the face-sheet.The maximum displacement of impacting center increases with increasing the impacting velocity or the mass of impactor.Thinner face-sheet tends to have a greater impacting displacement.Secondly,based on the FEM for the pre-stressed composite pyramidal lattice structures under low-velocity impact,the influences of different tensile or compressive prestresses on the impact response and damage are investigated,respectively.The results indicate that prestress has no significant influence on the peak contact load,contact duration or rate of total energy absorption,while it plays an important role on the deformation and range of damage.When the impacting velocity is constant,with increasing the tensile prestress,the maximum deformation of impact center inclines to increase but those of bottom face-sheet and truss cores tend to decrease.However,the effects of compressive prestress on the structural deformation are otherwise.The damage area of the upper face-sheet increases as tensile prestress increases,but it is hardly changed by compressive prestress.Finally,a FEM for the pre-stressed honeycomb sandwich structure under low-velocity impact is established.Under three different impact energy(1.0J,2.5J and4.0J),the influences of tensile prestress on the impact damage,time history of contact force,structural deformation and energy absorption are investigated,respectively.Theresults show that the whole impacting process is affected both by the contact stiffness and the extent of the impacting damage,which are directly or indirectly influenced by prestresses.Under small impacting energy and prestress,the stiffness of the structure caused directly by prestress become the main reason why prestress influence the impacting process.Under greater impacting energy or prestress,the main reason,however,is the impacting damage affected indirectly by prestress.The results have some theoretical significance and reference value for the design of composite sandwich structures.