Study On Fatigue Characteristics Of Fiber Metal Laminate Riveted Joints

Fiber metal laminates(FMLs)combine the advantages of traditional metal materials and fiber composite materials,are lightweight,have high specific strength,specific stiffness,damage tolerance and outstanding fatigue resistance.When the FMLs is used as aircraft skin,it is always connected with aircraft frames by riveting.During the flight of the aircraft,the riveted structure of fiber metal laminates is constantly subjected to high-frequency vibration,and a small relative displacement between the fiber metal laminate near the rivet hole and the frame is generated,which is prone to fatigue damage.In order to avoid the occurrence of catastrophic accidents,it is necessary to predict the fatigue damage of the fiber metal laminates in advance,so as to timely maintain and replace the components.Therefore,it is of practical significance to study the fatigue characteristics of fiber metal laminate riveting and predict its fatigue life.In this paper,the glass fiber aluminum alloy laminates as the research object are studied from the following aspects.(1)A three-dimensional finite element model of the riveted structure of glass fiber aluminum alloy laminates was established by using ABAQUS finite element software.And the critical plane method and related fretting fatigue criteria were introduced in detail,which provided the basis for the selection of fatigue criteria.Finally,the SWT fatigue parameters based on the critical plane method were selected to study the fatigue characteristics and predict the fatigue life of the riveted structure the fiber metal laminates.(2)The fatigue characteristics of fiber metal laminates were studied based on the finite element model of laminates.According to the SWT criterion,the distribution and variation trend of fatigue damage parameters on fiber metal laminates were calculated.The influence of plate width,margin and aluminum alloy ratio on the riveting characteristics of the laminate was discussed.The results show that the fatigue parameters of the laminate decrease gradually with the increase of the plate width and margin.When the plate width is 48mm and the margin is 21mm,the influence of the change of laminate size on the fatigue damage parameters tends to be stable.Fatigue parameters are more sensitive to the change of plate width.In the same thickness of fiber metal laminates,the larger the proportion of aluminum alloy,the smaller the fatigue damage parameters.(3)The effects of load parameters,such as cyclic tension,pretension and friction coefficient,on the fatigue properties of fiber-reinforced metal laminates were studied.The results show that the maximum value of the fretting fatigue damage parameter appears on the contact surface of the laminates,5.5mm-6mm away from the hole center,no matter the cyclic tensile force;The preload is helpful to prolong the fretting fatigue life,but it should not be too large.Changing the friction coefficient can affect the fatigue characteristics of the laminate by affecting the friction force of the contact surface.With the increase of the friction coefficient,the failure position of the fiber metal laminate gradually moves from the hole edge of the narrowest cross-section face to the position about 3mm away from the edge of the hole on the contact surface of the laminates.the failure position of the laminate is affected by the cyclic force and friction.(4)According to SWT life prediction formula,the fatigue life of fiber metal laminates is predicted,and lightweight laminates are selected.When the ultimate fatigue life is 1 X 106,the Glare3-2/1-0.5 laminate can bear large stress and light weight.