Failure Investigation Of Composite Stiffened Panel Under Compression

Advanced fiber-reinforced polymer composites are finding increasing application in aerospace due to their high specific strength arid stiffness along with other considerable advantages over metals. The stiffened thin-wall structures are widely adopted for structural efficiency they provide. However, despite years of extensive researches around the world, a complete and validated methodology for predicting the failure behavior of composite structures into post-buckling reign has not yet been fully achieved.Experimental and numerical investigations are conducted into the post-buckling behaviors and damage growth of advanced composite stiffened panels under compression. Adding the scaled eigenvalue buckling mode shape of the structure which occurred in the experiment to the nominal structure to approximate an imperfect pattern, the finite element method (FEM) analysis is implement with a combination of interacting nonlinear effects of large deformation and the reduction in material properties resulting from non-catastrophic degradation. To verify the analysis methodology adopted in the thesis, a compression experiment of an imperfect composite grid stiffened panel is carried out. The ultimate load obtained in the FEM simulation agrees well with the experimental data. Moreover, highly nonlinear structural events of mode shape changes are captured in the FEM analysis. The analysis methodology can be used as reference for the engineering design of composite stiffened structures.Additionally, behaviors of composite grid stiffened panels with a pre-existed circular delamination under compression have been analyzed in FEM. The effects due to different directions of the stiffeners to the delamination are discussed. On the basis of above, some basic work on utilizing piezoelectric material in shape control of the composite stiffened panel with a delamination is stated in the thesis.The work of this paper is supported by the project of the Chinese National Natural Science Foundation "The mechanism of piezoelectric smart composite structures with interface damage", Grant No.10872038.