Effects of structural layout on the joint strength of the stringer/skin interface of composite stiffened panel

The relationship between structural layout parameters and the critical delamination growth load of bonding interface between the skin and stringer is discussed in this paper, by which the residual strength of a composite stiffened panel with initial damage could be evaluated. The critical load data is fitted by parametric numerical sampling technic and the response surface surrogate model, which could be considered as the design curve representing residual strength of a damaged structure. According to the analysis data, under the effect of delamination buckling, the crack extension might be accelerated if stringers are too densely arranged. Considering that the debonding failure might be caused by the large deformation of buckling modes, a layout design method of stiffened panel is proposed in this paper, in which the stringer layout parameters under allowable load index is sized by the surrogate model of interface joint strength, as well as the explicit approximation model of skin local buckling based on energy variation principle. By this approach, a value range of stringer interval could be derived by combining constraints of different failure modes, and the joint strength for the stringer/skin interface could be guaranteed by choosing stringer layout parameters in this range. Finally, the layout design of a large scale composite wing panel is performed to validate the feasibility of the method in this paper.