Constitutive Model For Composite Layered Structures With Paper Sandwich Core And Polyethylene Foam

The paper sandwich core and polyethylene foam composite layered structures were a new type of cushioning energy absorbing structure,which combines the excellent bearing capacity and cushioning energy absorption characteristics of paper corrugated,paper honeycomb and polyethylene closed-cell foam.It expanded the application scope of cushioning packaging materials in product protection and packaging engineering.In this dissertation,the mechanical models and the constitutive relation of out-of-plane compression characteristics of those structures were studied by means of experimental,numerical and theoretical analysis.The main work of this dissertation as follows:Firstly,the out-of-plane static compression characteristics of paper honeycomb,paper corrugated and polyethylene foam were studied by static compression test.The characteristics of compressive stress-strain curves and its main parameters of monolayer porous structures were obtained,which provided support for further analysis of the mechanical model of composite layered structure.Secondly,the mechanical models and its constitutive relations of monolayer porous structures under out-of-plane static load were analyzed.Taking the corrugated core element as the typical volume element,the formulas for calculating the yield strength and crushing strength of the corrugated sandwich structure were derived by using the engineering cantilever model and the law of conservation of energy.Taking a single honeycomb cell in the honeycomb core as the analytical element,the buckling and crushing behaviors of the honeycomb core element were studied by using the classical buckling theory and the super folding model.The theoretical prediction formulas of yield strength,platform stress and compaction strain of honeycomb sandwich structure were analyzed.The theoretical prediction formula of compaction strain of polyethylene closed pore foam was discussedThirdly,the constitutive relations of monolayer porous structure material were established and the parameters of the constitutive relation were identified based on the stress and strain data of corrugated sandwich structure,honeycomb sandwich structure and polyethylene foam under static compression.The rationality of the constitutive relation was verifiedFinally,based on the constitutive relation of single-layer structure,the constitutive relations of composite layered structures with paper sandwich core and polyethylene foam were established by using the piecewise function method.The parameters in each piecewise constitutive relation were identified.