Upper and lower bound buckling load of perfect and delaminated fiber-reinforced composite columns

In this paper, a re-look into the upper and lower bound solution to the buckling of composite columns is presented in details and this includes the complete derivation of the expressions for the kinematical compatibility conditions. Included in this contribution are also the results of the current finite element simulation together with the results of the experiments. Moreover, further investigations are conducted to test whether the proposed three methods of calculating the effective flexural stiffness can be employed in cooperation with the developed mathematical model to form the desired upper and lower bounds for the buckling loads of both the perfect and single-delaminated fiber-reinforced composite beams for the various parameters that are studied. In these analyses, single-delaminated fiber-reinforced composite beams which consist of random ply-orientations and stacking sequences are employed to put up a stringent test on the generalness and applicability of these three methods. It is observed that for all the cases that were examined, these three means of evaluating the effective bending modulus of a fiber-reinforced composite beam pass are validated.