Investigation On Stamping Forming Limit And Failure Mode Of Viscoelastic Sandwich Steel/CFRP System FMLs Materials

The lightweight of automobile is an important means for the automobile industry to deal with energy crisis and environmental pollution in recent years.At present,the most popular lightweight materials in the automotive industry are High Strength Steel(HSS)and Carbon Fibre Reinforced Polymer(CFRP).This paper proposes to combine the above two lightweight materials to obtain new Steel/CFRP-system-FMLs(Fiber Metal Laminates)components with more outstanding and comprehensive performance in a car body.At present,preliminary research results on the basic mechanical properties and forming properties of FMLs materials have been obtained at home and abroad,but the research on the forming limits and fracture failure modes of FMLs materials is rare.Therefore,in this paper,I have studied the forming limit and failure mode of the new Steel/CFRP system materials(abbreviation: FMLs material)with the punch bulging experiment.The main research contents are as follows:(1)The forming limit experimental research scheme of FMLs materials was designed,and the temperature of the materials with a higher forming limit is identified as 80 ?.At this temperature,the punching bulging experiments of the coreless steel plates,CFRP composites and FMLs materials were completed by using forming equipment respectively;(2)The forming limits of FMLs materials affected by fiber layup method,strain path,punching velocity and the number of CFRP layers were compared respectively.The influence law and mechanism of the above factors on the stamping forming limits of FMLs materials were explored.The research results show that compared with unidirectional orthogonal layup FMLs and quasi-isotropic layup FMLs,woven layup FMLs have higher forming limits,and a reasonable increase in the stamping velocity and the number of CFRP layers helps to increase the forming limits of FMLs materials;(3)The forming limits of CFRP composites and FMLs materials with corresponding layup were compared,it is found that the presence of steel plates would reduce the forming limits of CFRP materials for narrow specimens(w?90 mm).Atthe same time,the forming limits of coreless steel plates and FMLs materials were compared,it is found that the forming capabilities of the four materials ranks as follows: coreless steel plate> woven layup FMLs> unidirectional orthogonal layup FMLs> quasi-isotropic layup FMLs;(4)The failure modes of FMLs materials affected by different fiber layup methods,strain paths,stamping velocities and numbers of CFRP layers were analyzed from a macro perspective.The results show that FMLs materials exhibit obviously diverse and complex failure modes,and their failure modes are highly sensitive to changes in material lay-up method,strain path,and the number of CFRP layers,while the impact of stamping velocity on failure modes is not significant;(5)Based on the existing material parameters,with the aid of ABAQUS finite element analysis software,the bulging process of woven FMLs materials affected by different strain paths,punching velocities,and numbers of CFRP layers was subjected to finite element simulation.The simulated bulging depth,the maximum punching force and the experimental results were compared.It is found that the predicted values and the experimental results have a high consistency,and the prediction accuracy reaches 80%,which verifies the correctness and validity of the establishment of the finite element model.