Research On Bending Performance And Failure Mechanism Of Corrugated Core Sandwich Structures Based On Adhesive-bonding

With the energy crisis and environment pollution becoming more and more serious,energy conservation and emission reduction become the inevitable trend at present and in the future.And structural lightweight design is one of the main measures for energy conservation and emission reduction of automotive,high-speed trains,ships and civil aviation industry.Corrugated-core sandwich structure has been proved to be a very important lightweight structure and have used in many transport vehicles due to its high specific stiffness,high specific strength,good thermal protection ability,good vibration attenuation performance and noise reduction.During these years,to further improve the lightweight efficiency,many high-performance materials have been used in corrugated-core sandwich structures,and this is the main reason why corrugated-core sandwich structures are still a research hotspot and have broad application prospects.Among many connection methods for sandwich structures,glue joint has been widely used and studied because of its many advantages including uniform stress distribution,good fatigue and heterogeneous materials connection performance and low manufacture cost.However,the adhesive layer would cause relative slide and rotation between face sheet and core sheet.Therefore,the idealized assumption about the joint in the traditional mechanical analysis is no longer correct,and the effect of adhesive layer need to be reconsidered.Thus,in this paper,by focusing on the effect of adhesive joint,several fundamental researches on bending performance and failure mechanics of the adhesively bonded corrugated-core sandwich structure made of hot forming super-high strength steel and carbon fiber reinforcement plastics(CFRP),respectively.At last,based on the research of equivalent elastic constants and failure mechanics in three-point bending,both homogenous material design system and hetoregeneous materials design system have been discussed through low-velocity impact FEM analysis of adhesively bonded corrugated-core sandwich bumper.And the results show that hetoregeneous materials design system perform best in both low-velocity impact and lightweight,which indicates that adhesively-bonded technique is very important in corrugated-core sandwich structures.The main research contents are as followed:(1)Considering the relative slide and rotation between face sheet and core sheet caused by adhesive layer,an analytical model has been developed for predicting the equivalent elastic constants of adhesively bonded corrugated-core sandwich panels.Through simulation calculation,the analytical model has been validated with good accuracy.Besides,by comparing the traditional analytical model with idealized joint assumption,the differences of the models and their equivalent elastic constants results have been discussed,and the effect of adhesive layer has been proved to exist.Then,based on the analytical model,the effects of adhesive joint parameters on equivalent elastic constants have been investigated.(2)Relative slide between face sheet and core sheet caused by adhesive layer would affect face sheet deformation during three-point bending.With this as a prerequisite,the analytical model for initial failure analysis of adhesively bonded corrugated-core sandwich beam has been deduced and constructed.Through both simulation and experiment method,the analytical model has been proved to be validate enough.Comparing to those based on idealized joint assumption,the model in this paper can accurately predict the initial failure modes of adhesively-bonded corrugated-core sandwich beams.At last,by using this model,the failure mechanics maps of different geometry parameters have been constructed,and the effects ofadhesive layer thickness and adhesive joint width on initial failure loads have been revealed.(3)During the research on CFRP adhesively bonded corrugated-core sandwich beam,on the one hand the analytical model for initial failure analysis of adhesively bonded corrugated-core sandwich beam under three-point bending has been extended according to the previous work and interlaminar stress analysis of CFRP laminates,so that it can predict initial failure mode and load of CFRP adhesively bonded corrugated-core sandwich beam.On the other hand,through a special finite element modeling method for CFRP laminates,the delamination failure process can be calculated in simulation.And comparing the corresponding experiments,this modeling method has been proved to be effective on delamination simulation.(4)The adhesively bonded corrugatd-core sandwich bumper has been designed by hetoregeneous materials system with hot forming steel and CFRP laminates.Based on both elastic constants and failure mechanics research,the initial failure load and the corresponding center displacement are calculated.The multi-objective optimization of several different materials design systems has been carried out with mass and initial failure load as optimize object and center displacement as limiting condition.The heterogeneous materials design system is proved to be the best.At last,through low-velocity impact FEM analysis,the lightweight performace of both homogeneous and heterogeneous materials design system have been compared and discussed.The results show that the heterogeneous materials design system has been proved to be best in lightweight impact performace.