Damage Analysis Of Composite Envelope Based On Peridynamic Theory

In recent years,due to the rapid development of the composite material field,the proportion of composite materials in aircraft skin has become increasingly high.Composite material skin has the characteristics of lightweight,high specific strength,and superior vibration reduction performance.However,due to the anisotropic nature of the material itself,it exhibits obvious geometric nonlinearity under load,and its mechanical properties are relatively complex.The initiation and propagation of wing skin cracks are the main causes of aircraft structural failure.Therefore,reasonable prediction of the crack propagation path and failure form of composite materials is an engineering problem that must be considered when applying composite materials to skin structures.This article introduces the current research status of near-field dynamics at home and abroad,as well as its applications in the field of composite materials.Based on the basic theory of near-field dynamics,the motion equation of bond based near-field dynamics is derived.Fiber bonds and matrix bonds are introduced in the single-layer composite plate,interlayer bonds and shear bonds are introduced between layers.The analytical expressions of four bond constants are derived,and the near-field dynamics models of composite single-layer and laminated plates are constructed.Secondly,based on the near-field dynamics model of composite materials,FORTRAN language was used for program design to analyze the impact of prefabricated cracks with different angles,positions,and forms at the center on the damage mode of single-layer plates,as well as to simulate the crack propagation process and failure mode of laminated plates with central cracks under different boundary conditions.The results showed that the matrix bonds of composite materials are more prone to fracture under velocity loading,Cracks that initiate and propagate along the fiber direction will occur;As the velocity load increases,the damage of laminated plate structures becomes increasingly complex and difficult to predict.In order to verify the accuracy of the simulation,a rapid tensile test of laminated plates was designed and conducted.Carbon fiber prepregs from different angles were arranged and combined in different layering sequences to obtain the carbon fiber laminated plates used in the experiment.The experimental and simulation results were in good agreement.Finally,the composite material damage near-field dynamics program was applied to composite skin components.Taking fixed wing drones and Airbus A320 wing skins as examples,the skin materials in actual working conditions were discretized into flat plate models,and a near-field dynamics model of the skin structure was established to simulate the common crack propagation process and failure modes of composite skin structures,The results show that the damage mode of fixed wing unmanned aerial vehicles is roughly the same as that of common laminated panels,which is in line with theoretical prediction and actual results;Due to the rapid boundary velocity,the cracks generated in the Airbus A320 skin structure are different from the common crack propagation of laminated plates.However,no matter how complex the crack propagation is,cracks are always prone to occur in the fiber direction,providing a reasonable basis for damage prediction of skin structures in the aerospace field.