Research On Influence Of Interfacial Defects On Ultimate Bearing Capacity Of Reinforced Composite Panel

Carbon fiber reinforced composite stiffened panel is one of the most important connecting structures in modern aircraft.Usually the stiffened plate structure consists of two parts: skin and flange,manufactured by using secondary bonding,co-bonding or co-curing.However,the manufacturing processs of laminated composite materials can lead to the appearence of defects in the bonds.And during service,due to the effect of out-of plane load,the defect will lead to further expansion of delamination damage,cracks will be presented in the material before the application of the design loads.In this paper,aimed at the defect existed in reinforced composite panels,experimental study and numerical research have been used to study the influence of the size and position of the defect and flanges chamfer on ultimate bearing capacity of reinforced composite panels,which would provide theoretical guidance for the determination of damage tolerance of reinforced composite panels in engineering applications.Firstly,this paper reviews the damage failure method for structural failure of composite laminates.The theory of in-plane damage and interlayer damage failure was introduced,and the advantages and disadvantages of each model were analyzed,which would provide a theoretical foundation for the analysis of the test results of the reinforced composite panels structure and the strength prediction of the numerical simulation.Secondly,to study the ultimate load-carrying capacity of reinforced composite panels under three-point bending loads,and provide model data and verification basis for subsequent finite element simulation calculations.In this paper,experimental methods were used to study the ultimate load-carrying capacity of reinforced composite panels.The results show that: interface defects reduce the bearing capacity of the structure;the load capacity of the structure is very sensitive to defects at the middle of interface;interface defect changes the damage mode.Then,to study the effect of interface defect size and position on the ultimate bearing capacity of the structure.In this paper,numerical analysis method was used to study the ultimate load-carrying capacity of reinforced composite panels.The size and position of interface defects on the bearing capacity of the structure and analysis of structural damage patterns and failure mechanisms were studied.The results show that: the effectiveness of this model has been verified;the load capacity of the structure is found to decrease with increasing defect size;structural bearing capacity is sensitive to defects in the middle of the interface;interface delamination is the cause of structural damage;interface delamination is mainly due to peeling failure.Finally,to study the effect of flange chamfer on the ultimate bearing capacity of the structure.three-point bending experiment was performed on stiffened panels with right angles,the experimental results were verified by the finite element method.Then,the finite element model of reinforced wall panel with 27°,45° and 90° degrees was established,and the finite element model of stiffened wall with defects under different chamfers was established.The results show that: the effectiveness of this model has been verified;when the flange angle is 45°,the ultimate bearing capacity of the structure is the best;interface defects reduce structural ultimate load carrying capacity.