Preparation And Mechanical Properties Study For Polyurethane Sandwich Plate

Polyurethane sandwich plate was a quickly developed structure at recent years and was wildly used in shipbuilding,aeronautics,astronautics,building and so on.It is composed of two pieces of metal or fibre,faceplates and one polyurethane core.Polyurethane elastomer sandwich plate and polyurethane foam sandwich plate were the most widely used.High strength,rapid reparation and better industrialization are its advantages.And the existing of Polyurethane make it also has many special additional properties,such as weight reduction,resisting impact,dynamic response,enhancement in the random fatigue behavior,significant acoustic performance and heat insulation.However from the actual project,there are still many difficulties,such as the influence of structure performance considering the glue effect,the damage extension process of glue defect,the damage extension process of internal parts,etc...The domestic research was still in the initial stage,and relevant research documents were still less,so the in-depth study has important application value.The two types of polyurethane sandwich plate are studied by this paper from the aspects of theory,experiment and numerical,including a new bending equivalent analysis method of sandwich plate considering glue effect,buckling performance of polyurethane elastomer sandwich plate containing circular glue defect,pull-off performance of polyurethane foam sandwich plate on embedded bolt joint,etc..and the main contents are listed as followings:1.The preparing method of polyurethane elastomer and fiber reinforced composite plate are studied,and the preparing experiment of the two types of polyurethane sandwich plate are carried out.Besides,the key technical in the experiments are given.And then,some tests of polyurethane elastomer and fiber reinforced composite plate are also completed.The results can provide datas for the follow studies.2.A new bending equivalent method of sandwich plate,considering glue effect,is proposed based on sandwich theory to provide theoretical for the bending design of sandwich plate in actual projects.First of all,The panel and glue are equivalent to a single layer material by the laminated plate theory,and then the equivalent bending equation of sandwich plate,considering the glue effect,is build with Reissner theory.This method avoid the disadvantage of establishing complex equations,and can be easily understood to apply by engineers.On the basis of this equivalent method,the bending deflection of polyurethane elastomer sandwich plate considering glue effect are carried out to calculate under simply supported.3.In view of the glue defect exists in the actual project,the buckling numerical model of polyurethane elastomer sandwich plates,containing the circular glue effect,is build to analyze the damage extension process of circular glue defect.(1)The buckling experiment of polyurethane elastomer sandwich plate with no defect are carried out to obtain the damage form and the critical buckling load.On the basis of this results,the buckling numerical model of polyurethane elastomer sandwich plate with no defect is build,and the accuracy is demonstrated.(2)To get the energy release rate of polyurethane elastomer core sandwich plate,the DCB and SLB experiment of polyurethane elastomer sandwich plate are carried out,combining the theory of fracture mechanics and the virtual crack closure technique.(3)The buckling numerical model of polyurethane elastomer sandwich plates,containing the circular glue effect,is build to analyze the deflection of the radius parameter for the buckling performance and the damage extension process of glue.4.Pull-off experiment of polyurethane foam sandwich plate,containing the numerical model are carried out to solve the complex problem of internal damage and damage evolution process of sandwich structure in the actual project(1)To get the macroscopic failure mode and the failure load,the Pull-off experiment of polyurethane foam sandwich plate are carried out.(2)In the base of the stretching experiment results of fiber reinforced composite plate,the numerical model are carried out and the damage UMAT subroutine is compiled to analyze the damage extension process of fiber reinforced composite plate.(3)In the base of the pull-off experiment of polyurethane foam sandwich plate,the numerical model including using material subroutine UMAT for fiber reinforced composite plate damage,XFEM extended finite element method for polyurethane foam fracture failure and cohesive finite element method for adhesive layer are carried out to analyze the damage extension process and show the failure mechanism.Furthermore,the influence of the embedded bolt parameters on pull-off strength and damage propagation are discussed.Optimization Suggestions on the embedded bolt parameters are proposed.