Study On The Impact Damage Resistance Of Hybrid Composite Sandwich Structures

The honeycomb sandwich structure is a typical structure to realize lightweight design,which is widely used in transportation.In the process of actual transportation,low-velocity and heavy load impact events often take place,such as dropping impact and collision.Moreover,the honeycomb sandwich structure is extremely sensitive to impact damage,which will lead to significant degradation of the strength and stiffness.Therefore,it is necessary to study the impact resistance of the honeycomb sandwich structure when subjected to the impact of low-velocity and heavy load.The impact damage resistance of the hybrid composite sandwich structure is focused on,which is made up of high ductility and high strength carbon/glass fibre hybrid composite skins and NOMEX honeycomb.The research details are as follows.Based on the study of the three-dimensional progressive damage failure theory,the constitutive relation of the orthotropic material is established,and the damage initiation criterion,damage evolution and stiffness degradation are determined.Furthermore,a three-dimensional progressive failure model of woven fabric composite is established.Not only the intra-laminar damages but also the inter-laminar damages involving six damage modes are considered in this three-dimensional progressive failure model.At the same time,the isotropic ideal elastic-plastic constitutive relation is used as the constitutive relation of NOMEX honeycomb core.It provides the theoretical basis for the following study.Based on the determination of the constitutive relation of NOMEX honeycomb core,a numerical simulation of the honeycomb sandwich structure with the core height of 20 mm under out-of-plane compression is carried out.The result of finite element method(FEM)analysis is compared with the result of out-of-plane compression test firstly.With the verified accurate FEM,the effects of honeycomb core height,wall thickness and cell size on the mechanical performance of the honeycomb sandwich structure are further investigated.The deformation process and failure mechanism of honeycomb core under out-of-plane compression are also analyzed.It provides a foundation for the next research on the impact resistance of honeycomb sandwich structure under low-velocity and heavy load.Based on the study of the three-dimensional progressive damage failure model and the out-of-plane mechanical performance of NOMEX honeycomb core,the impact resistance of honeycomb sandwich structure under low-velocity and heavy load is further studied.The damage modes,peak force and energy absorption(EA)of honeycomb sandwich structures with different core heights under low-velocity and heavy load are analyzed by numerical simulation.The results of FEM analysis are compared with the results of the corresponding impact tests to verify the accuracy of the numerical simulation.With the verified accurate FEM,the effects of honeycomb wall thickness,cell size and impact energy on the peak force,EA and specific energy absorption(SEA)of honeycomb sandwich structures are systematically investigated.The influence of honeycomb structure parameters on the impact damage resistance of hybrid composite sandwich structure is focused on in this study.The relation between honeycomb structure parameters and the damage mode,peak force,EA and SEA is analyzed.The study will provide a reference for lightweight design of honeycomb sandwich structure.