| With the implementation of China’s "automotive industry development plan(2021-2035)",especially the proposal of the declaration on "carbon peak,carbon neutral",the automotive industry has increasingly strict and urgent requirements for lightweight technology.In recent years,Steel/CFRTP fiber metal laminated panel body components made of high strength steel(HSS)plate and carbon fiber reinforced thermoplastic composite materials(CFRTP)have attracted the attention of industry and academia at home and abroad.Although the research on the basic mechanical properties,formability,fatigue resistance and impact resistance of FMLs has made a lot of achievements,the research on the bonding effect and bonding strength between metal layer and composite layer in FMLs is still in its infancy,and the problem of inter-laminar strengthening and toughening of FMLs still needs to be further studied.Therefore,in this paper,a new strengthening and toughening process and method based on the macro and micro combination characteristics of metal surface and short carbon fiber reinforced phase is proposed for Steel/CFRTP system FMLs.The effects of combination characteristic parameters,hot pressing process parameters and other factors on the strengthening and toughening effect of FMLs interface are studied by experiment and simulation.(1)Based on the rheological properties of thermoplastic carbon fiber composite layer in Steel/CFRTP system FMLs and the good processing technology of steel plate layer,a new interface strengthening and toughening process and method were proposed to improve the inter-facial bonding strength and fracture toughness of Steel/CFRTP by constructing the macro micro combination characteristics of metal layer surface and introducing short carbon fiber reinforcement phase.The interface strengthening and toughening process scheme was proposed.(2)With the help of single tension shear test,the effects of different "macro groove and micro hole" combination characteristics and short carbon fiber reinforced phase on the failure mode and failure behavior of Steel/CFRTP interface were studied,and the influence mechanism was deeply analyzed,which confirmed the feasibility and effectiveness of the proposed process scheme.(3)Based on the interfacial bonding effect,maximum failure load and fracture energy absorption,the influence of micro cone parameters(diameter depth ratio)on the interfacial bonding strength of Steel/CFRTP was explored.It was found that the smaller the value of micro cone diameter depth ratio was,the better the interfacial bonding strength of Steel/CFRTP was.In addition,the cross-section observation of failure samples was used to study the short carbon steel interface The mechanism of fiber interface bridging and toughening,especially the influence of the filling state of molten resin on the strengthening and toughening effect of Steel/CFRTP interface and the control measures.(4)In view of the negative influence of carbon fiber on the filling state of resin in micro taper hole,the influence law and mechanism of hot pressing temperature,taper hole size and die pressure on the filling effect of short fiber resin melt in micro taper hole were explored.By optimizing hot pressing process parameters,the adverse influence of short carbon fiber on the filling effect of resin matrix was reduced,and the bridging and toughening effect of short carbon fiber was promoted.(5)The finite element simulation method was used to predict the shear failure mode and failure behavior of Steel/CFRTP interface under different macro micro combination characteristics of metal layer surface.By comparing with the experimental values,it was found that the simulation results of Steel/CFRTP single lap joint with different macro micro combination characteristics of metal layer surface were highly consistent with the experimental results,which verified the established model The accuracy of the simulation model and the effectiveness of the combination of macro and micro characteristics of the metal layer surface on the Steel/CFRTP interface strengthening were verified. |
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