Investigation On Low Velocity Impact And Residual Compressive Properties Of Reinforced Composite Skin Plate

Carbon Fiber reinforced composites(CFRP)have the characteristics of specific strength,high specific stiffness and strong designability,and are widely used in the design of aerospace structures.Lightweight and large-scale structures are the development trend of aircraft structure design.Composite reinforced structures have the characteristics of high axial load-bearing capacity,high strength and high rigidity,and are valued by aviation,automotive and wind power industries.However,the impact resistance of composite materials is weak,and the impact will cause serious damage to the structure,while low-speed impact damage is concealed.The low-speed impact damage will expand during use,which will seriously affect the load-bearing capacity of the structure.Therefore,it is of great significance to study t he impact damage caused by lowvelocity impact in reinforced composite structures and the residual bearing capacity of structures containing impact damage.In this paper,three groups of impact tests are designed according to the possible impact locations of CFRP stiffened plate in practical application.The three locations of the stiffened structure are impacted respectively.The damage forms and damage sizes of the specimens are detected by visual inspection method and ultrasonic C-scan system,and the damage differences of different locations are compared.The axial compression test is designed to observe the failure modes of the specimens And test the residual compressive strength of the specimen.The finite element software ABAQUS was used to simulate t he impact and post impact compression of composite stiffened plates.The damage forms of composite stiffened plates under impact and the damage propagation process of stiffened plates with impact damage under compression were studied.The three-dimensional Hashin failure criterion based on strain is introduced to simulate the failure process of fiber and matrix through VUMAT subroutine interface,and the cohesive force model is used to simulate the delamination propagation of composite stiffened plate.The validity of the finite element model is verified by comparing with the experiment.Combined with the test and finite element simulation results,it can be seen that: when there is no stiffener below the impact point,the main impact damage mode is fiber fracture and delamination inside the skin,which has little impact on the structural bearing capacity;when there is stiffener support below the impact point,the delamination damage area in the skin is small,but the debonding between the stiffener and the skin is serious,which seriously affects the residual bearing capacity of the structure,especially under the impact point When it is the intersection of longitudinal stiffeners and transverse stiffeners,the bearing capacity of the stiffened plate decreas es by44.74%.