Testing And Numerical Analysis Of “Ex-situ” Toughened Stiffened Composite Panels

Composite stiffened panels are widely used in aviation engineering. Debonding and failure often occur at the interface of the stringer and the skin as its poor toughness, which hinders the development of composite in the structure of airplanes. According to this situation,domestic scholars provided a method to toughen the interface—the "ex-situ" toughening technology, which could greatly raise the toughness of the interface and improve the performance of composite structures.In this paper, three-point bending static tests, three-point bending fatigue tests and axial compression static tests were set up towards a series of "ex-situ" and "unex-situ" toughened composite stiffened panels to compare and research the performance of two kinds of interfaces. In static tests, strain gages were used to analyze the initial debonding and damage propagation of the structure. In fatigue tests, the cyclic loading times and the length of delamination were recordedin the real time to analyze the spread rate of delamination of different interfaces.Then towards static tests, a progressive damage FE model of the composite stiffened panel was established via Abaqus to study the mechanisms of interface damage and final failureof the structure.This approach employed Hashin failure criteria andmaterial stiffness degradation, and it was able to predict the damage initiation and evolution. Towards fatigue tests, the test and VCCT results were combined to research the relationship between the spread rate of delamination and the strain energy release rate.