Effect of hygrothermal condition on buckling and post-buckling performance of CCF300/5228A aero composite stiffened panel under axial compression

CCF300/5228A aero composite stiffened panels achieved absorbing saturation in hygrothermal condition (70? distilled water), whose absorbing process followed the Fick law. Many debonding and gaps of matrix to fibers could be observed after hygrothermal exposure by scanning electron microscope (SEM). Compressive experiments were conducted on unaged and aged composite stiffened panels. Failure modes of the two types of specimens are quite similar with several major ways, including the debonding and fracture of stiffeners together with the splitting and ripping of panel. Buckling patterns for both types of specimens are similar and characterized by buckling of panels between stiffeners and buckling of the middle two stiffeners. However, the bending direction of buckling mid-panel for aged specimens is opposite to that of the unaged at same position panel, which shows that hygrothermal condition influences the bending direction of buckling mid-panels seriously. There still exists a post-buckling process for aged specimens under axial compression, whose average buckling load and failure load decrease by 3.1% and 22.2% respectively, comparing to that of unaged specimens.