Study On Mechanical Property Of Variable Angle Composite Structure With Defect

With the rapid development of aerospace industry and the continuous progress of composite material manufacturing technology,the application of advanced composite material structure is more and more extensive.As a key technology to manufacture complex composite structure,automatic wire laying technology has great advantages.However,when laying complex curved structure,it is necessary to change the fiber Angle and re-lay the cutting fiber.In the process of forming,the Angle defect of the wire bundle will be formed,which will affect the mechanical properties of the structure.In order to perfect the modeling method of the composite materials with automatic wire laying defects and enrich the relevant database,the influence of the Angle defects of the wire bundles on the mechanical properties of laminated plates and curved stiffened composite panel was studied by combining experiment and numerical simulation.Based on the principle of control variable method,the influence of Angle size and Angle overlap on the mechanical properties of laminated plates was studied.In order to accurately simulate the actual defect distribution state of laminated plates,based on the principle of discrete method and the assumption of continuous linear change of fiber Angle,Python was used to write a script to realize the defect location through a loop so as to give the corresponding attributes to complete the modeling,and the simulation was carried out under the corresponding experimental conditions.In numerical simulation based on Hashin criterion and rule of Ye criterion,the user subroutine is written to determine the failure mode and the dominant factors under various loading conditions.The camanho stiffness degradation criterion based on the experiment is used to realize the stiffness degradation of the material.The progressive failure analysis of the laminated plate and the stiffened composite panel is completed,and the bearing capacity of the laminated plate and the stiffened composite panel is predicted and evaluated.By comparing the experimental results with the numerical results,it is proved that the modeling method used in this paper is effective,and the two results were in good agreement with each other,and the failure modes and failure locations were basically the same.It was also found from the numerical simulation results that the existence of defects changed the local stress state and the distribution of element failure after failure.The influence of defectson the bearing capacity of laminated plates is generally controllable,but the influence of defects on the strength under specific working conditions is more than 20%,which should be paid attention to and avoided as far as possible in engineering practice,while the ultimate strength and stiffness are not sensitive to defects under certain working conditions.The results achieved from study of laminated plates were applied to the Angle defects of local wire bundles of curved stiffened composite panel,the influence of defects on the bearing capacity was determined by analyzing and comparing the load-displacement curves under compression load,and the failure modes of stiffened composite panel were determined by analyzing the damage evolution and stiffness degradation.The research shows that the existence of defects changes the local stress state and affects the bearing capacity of the stiffened panel,so it is necessary to improve the wire laying process to reduce the number and scale of defects.