Study On Damage And Fatigue Characteristics Of Riveted Joints In Fiber Metal Laminates

Fiber Metal Laminates(FMLs)are hybrid composite structures made of alternately layered metal sheets and fiber reinforced composites in a certain curing temperature and pressure.They combine the good elasto-plastic properties of traditional metal materials and high strength and high temperature resistance of fiber reinforced composite.FMLs have gradually replaced traditional materials with their superiority of fatigue resistanc corrosion resistance,high specific strength and high specific rigidity.Although FMLs riveted structures are widely used in aircraft skins and and other fields,the researches on the FMLs riveting damage mechanism and fatigue characteristics are still rare,which has practical and engineering significance for FMLs riveting design.In this paper,the research object is riveted FMLs,and the following research contents were carried out by combining experiment and finite element simulation.(1)The material properties of aluminum alloy and glass fiber reinforced composites were measured,and the influence of all direction parameters on the strength and failure of composites was explored.The failure mechanism of composite materials is understood and the basis for the selection of its failure criteria was provided.(2)A three-dimensional finite element model of FMLs riveting was established,and the three-dimensional Hashin progressive failure criterion and interlayer delamination model were introduced in the finite element model,and the damage mechanism process of FMLs riveting under static load was predicted,and the multi coupling damage behavior of FMLs riveting was explored.The FMLs riveting model is in good agreement with the experiment,which is consistent with the continuous damage mechanism from the damage initiation to complete failure.The accuracy of the 3D Hashin damage criterion and the accuracy of the model parameters are verified,which lays the foundation for the study on the influencing factors of FMLs riveting.(3)Based on FMLs layer plate riveting 3D finite element failure model,the residual strength research of FMLs layer plate riveting was carried out.The results showed that:In the case of a/t=0,the damage area of laminates is larger,which reduces the strength of FMLs riveting.The increase of the aluminum alloy fraction can improve the riveting strength of the laminates,but the riveting strength and the riveting strength decrease when the aluminum alloy fraction is greater than 50%.The more the number of lay up.the more serious the free end of riveting hole peel off is,and the strength of riveting is weakened.The increase of pretension can delay the damage initiation of fiber and matrix,and enhance the stiffness of riveting.With the increasing of W/D and E/D,the strength of laminate riveting is improved,but the riveting strength is no longer obviously increases when W/D>3 or E/D>3,and the failure mode of laminate riveting is also maintained as an ideal bearing.(4)The fatigue tests were carried out to understand the fatigue properties of FMLs single riveting The results showed that:Under certain pretension conditions,the fatigue crack does not initiate on the edge of the hole of FMLs single riveting,but is more likely to produce cracks at the edge of the rivet head,and FMLs single riveting fatigue life of the crack path is predicted.(5)The strength analysis and life reliability prediction of a wing skin riveting were studied.There is a local stress concentration in the riveting place of the skin and the I-beam,and the three rivets riveting can improve the tensile strength and relieve the stress concentration,but the reliability of the fatigue life of three rivets riveting is decreased.