Buckling of Composite Beam-columns with Stochastic Properties

Abstract

Beam-columns made of polymer-matrix fiber-reinforced composite materials are increasingly being used in automotive, aerospace, structural, and mechanical engineering industries. Their buckling loads are of paramount importance in the design and development of high-performance composite mechanical components. Composite laminates display significant variability in their material, geometric, and structural properties. As a result, the buckling loads of composite beam-columns become stochastic variables. Therefore, in the design and failure prediction these variations have to be taken into account. The statistics of buckling loads are needed in the reliability-based design of composite structural systems. The first part of the paper considers the buckling of prismatic composite beam-columns with the objective of determining the mean values, mean square values, and standard deviation values of the buckling loads. The randomness in the material and geometric properties of the laminated beam-columns is modeled using homogeneous stochastic fields in space. The perturbation method is employed in the context of stochastic analysis. Using the sample realizations and the first-order second-moment probabilistic analysis the statistics of buckling modes are determined. The second part of the paper considers the local buckling of composite thin-walled beam-columns. In the design of thin-walled beam-columns local buckling is a priority over the global buckling. The bending rigidities are obtained based on the laminate analysis of flange and web sections. The local buckling analysis is conducted using the Ritz method in the context of stochastic plate analysis under uniaxial compressive forces and probabilistic characteristics of critical buckling loads are determined. A parametric study on both the prismatic and the thin-walled beam-columns made of NCT-301 graphite-epoxy composite material is conducted.