Improved correlation of predicted and experimental initial buckling stresses of composite stiffened panels

Abstract

Experimental and numerical investigations are conducted for rigorous correlation of initial buckling properties of stiffened panels made of carbon fiber/poly-ether-ether-ketone (CF/PEEK) and CF/epoxy. Decreasing longitudinal elastic modulus of unidirectional CF composites lamina in compression plays a key role for better numerical predictions. A consideration of end fixtures in finite element modeling plays another key role in correlation and both initial buckling stress and mode for the short panels used here. A quarter finite element model with an end fixture by hypothetical symmetry is considered as the irreducible minimum in the modeling. A careful setting of lamina thickness is also important for better predictions. Initial imperfection close to the real shape of CF/PEEK panels is taken into account and an improvement in correlation of predicted and experimental results is reached. A conventional Rayleigh-Ritz approach considering only a local buckling mode of skin is developed. This analytical prediction compares fairly well with the numerical and experimental results in the preceding work in which their stringers are stiff enough.