Research On Dynamic Mechanical Properties Of PMI Foam Sandwich Plate

Polymethacrylimide?PMI?foam is a lightweight,fully closed cell,high heat resistance and high specific strength,isotropy rigid foam.It is easy to be processed and make complex structural parts.It can be used RTM technology to make amount of composite materials which large object.It is an ideal core material for high performance composite sandwich structures.PMI foam sandwich structure is widely used in aerospace,traffic and protective devices,then,the dynamic mechanical properties of composite sandwich structures have drawn much attention.At present,the PMI foam with better mechanical properties becomes one of the hot points to study the energy-absorbing composite materials.Therefore,the research on dynamic mechanical properties of PMI foam sandwich structures has great significance.Firstly,the manufacture process of PMI foam sandwich structure was studied,and make different parameters sandwich specimens.The quasi-static compression test of the sandwich structure was carried out to determine its compressive strength and elastic modulus.The analysis of the stress-strain curve of sandwich structure shows that it is divided into three stages in quasi-static state:linear elastic stage,yield platform stage and densification stage.The influence of the thickness of the sandwich panel,the thickness of the core and the density of the core on the mechanical properties of the sandwich structure were analyzed by the control variable method.The results show that the density of the core has the greatest influence on the compressive strength and elastic modulus of the sandwich structure in the quasi-static state.28%reduction on density,the elastic modulus drops 41.20%and the compressive strength decreases 42.58%.Secondly,the dynamic impact compression experiment was carried out by using the Split Hopkinson Pressure Bar experimental device.The influence of the parameters of the sandwich structure on the mechanical properties under dynamic conditions is analyzed and compared with the quasi-static.The dynamic compressive performance of PMI foam sandwich structure was analyzed,the influence of the strain rate on the sandwich structure compressive strength was compared and analyzed.Finally,ANSYS/LS-DYNA dynamic analysis finite element software was used on the PMI foam sandwich structure numerical simulation.The deformation and energy absorption characteristics of PMI foam sandwich structure under impact load were analyzed.The numerical simulation and dynamic impact test were compared.The different parameters of sandwich structures on dynamic mechanical properties is compared by numerical simulation,finding out that the main factor affecting the dynamic mechanical properties of the sandwich structure was the core density.While the core density decreased by 28%,the effective energy absorption rate decreased by 45.66%.The results show that the strain rate increases from quasi-static 7.6×10^-4s^-11 to 150s^-1,the compressive strength increased by 29%.The strain rate increases from 7.6×10^-4s^-11 to 310s^-1,compressive strength increased by 43%.The effective absorption rate decreased slightly.