Failure Analysis Of Filling Zone Of CFRP-T Joints By Numerical Simulation And DIC Experiment

The composite integrated structure is the main application form of advanced composite materials in aerospace.As the basic unit of the composite integrated structure,the carbon fiber reinforced composite T(CFRP-T)joints need to transfer out-of-plane loads,and its mechanical properties will affect the bearing capacity of whole structure.In this paper,the bearing capacity,load response and failure form of CFRP-T joint under tensile load are studied by numerical calculation and experiments.The strain distribution and failure mechanism of high risk area-triangle area are mainly studied.The mechanical properties of the laminated structure of CFRP-T joints and the failure characteristics of the adhesive structure were analyzed.The finite element method(FEM)is applied to established a 3D model with laminated plate model and bilinear cohesive model to research the failure mode and bearing capacity of the joint under tensile load.The calculation results show that the failure load of the joint is 19.9KN,and the final failure form is the debonding of L-plate and skin plate.The static tensile load tests of CFRP-T joints are carried out,and the digital image correlation(DIC)method is used to obtain the strain distribution in the triangular area of the joint during drawing.The experimental results show that the failure load of CFRP-T joints under tensile load is about 20 KN,with a linear relation between load and displacement.The triangle filling region is the peak region of stress,including horizontal tensile stress and vertical compression stress in the middle,and shear stress at the end of the bottom.The ultimate failure forms are debonding of L-plate and skin plate caused by tensile normal stress and fracture of filling material caused by shear stress.By comparing the numerical simulation results with the experimental results,the validity of the 3D finite element model is verified,and the bearing capacity,strain distribution and failure form of the joint can be accurately predicted.The influences of the chamfering radius of the triangle region and the filling material on the load transfer and bearing capacity of the joint is analyzed by the finite element model.It is found that the chamfering radius can effectively improve the load transfer of the glue layer in the triangle area and improve the bearing capacity of the joint,but the effect of the filling material on the joint is not obvious.In this paper,the exploration of 3D Numerical Simulation of CFRP-T joints and application of DIC method in failure analysis of composite structure can provide reference for further research and the application of CFRP-T joints.