Structure Optimization Of Composite Stiffened Panel To Titanium Mechanical Joints

Due to its flexible designability, high specific strength and stiffness,composite materials are widely used in the field of aircraft design. However,by comparison with titanium alloy, the inevitable weaknesses of compositematerials, such as high performance disparity, anisotropism, low impactdamage tolerance, unpredictable fatigue life and expensive costs inmanufacturing, make the composite materials not able to substitute fortitanium thoroughly in aircraft structure. The exploration of an effectivecombination of these two materials is urged by the integrity design of flightvehicles. The bending stiffness of composite plates sometimes cannot satisfystructural demand, especially under bending load. Composite stiffened panelbecomes the basic structure in aircraft and space vehicle because of itsbending resistance capacity.The quasi-static tensile tests of composite stiffened panel to titaniummechanical joints structure were accomplished. The results show that there isserious stress concentration at the run-out place, which leads to the pre-failureof the structure. A3D finite element model is built up to simulate the testprocess, which takes the composite progress failure and titanium plasticproperty into consideration. The finite element model is verified bycomparing load-displacement and strain-load curves with experiments.A parameter study is made to study the joints strength influencing factors,including the fastener diameter, web indent distance and inclined angles of theend. The results show that when the fastener diameter is14mm, the compositestiffened panel can ultimate its property. The web indent distance and inclined angles of the end will both influence the stress distribution at the web end.The rational combination of the parameter can improve the structural loadcapability.The web optimization is made after choosing of the parameters. TheGlobal-local method is applied to improve the optimization efficiency.Topology optimization is ultimated in order to redesign the run-out shape. Thestructural strength is proved to be higher after optimization.