Study And Prediction Of Residual Strength Of Composite Stiffened Panels With Opening Crack

During the service use of composite stiffened panels,the material will degrade and produce various types of cracks.The current research mainly focuses on the influence of the opening on the ultimate strength and damage expansion of the composite stiffened panels,and it is not studied as a fracture problem,but only considers the damage forms such as fiber-matrix damage and lamination.In addition,opening design needs to be introduced in the process of assembly and use of specific structures,and the existence of opening will also have a certain impact on the separation of stiffener and skin.Therefore,it is of great significance to study the impact of opening crack on stiffened panels under compression / shear load.In this study,Hashin failure criterion and parameter degradation model were adopted to simulate the composite reinforced panel with openings,ignore the separation of stiffener-skin damage,to study the influence of openings of different angles and width on the stiffness and ultimate strength of composite stiffened panels under compression or shear load,and further analyze the final failure mode and damage extension of the stiffened panel.The compression failure of the opening stiffened panels,the destruction elements extend from the opening tip along the horizontal direction to the adjacent stiffener,and the destruction elements of shear failure expand from the point of the opening tip to the intersection of stiffener and frame.The cohesive zone model was used to simulate the bonding layer and study the influence of the opening of different lengths and angles on the composite stiffened panels material damage and interface failure.Under the compression condition,the opening is closer to the bonding layer,the greater the impact on the stiffener-skin separation damage and the tensile damage of the stiffener flange,the opening on the adhesive layer concentrates the damage around the opening.The impact of the same opening in the shear condition is not obvious,and the shear ultimate load even increase compared with the intact panel.A BP neural network model is set up to predict the ultimate compressive load of stiffened panels with opening and single stiffener.Take the position,length,width and angle as input parameters,and batch establish data sets through the secondary development of ABAQUS in Python.By evaluating the ANN learning effect of different network structures,it is found that the ANN model with 5-15-30-15-10-5-1 network structure and tanh as excitation function not only has good learning ability,but also has good generalization,and can accurately and efficiently predict the ultimate compressive load of single stiffened panel with openings.