Imperfection sensitivity analysis of the nonlinear stability of composite beams - Numerical and experimental investigations

An imperfection sensitivity analysis of the buckling and post-buckling behaviour of thin-walled GFRP laminate beams subjected to pure bending is presented. The FEM software based on Koiter's asymptotic theory was developed. For the imperfection sensitivity analysis, the Monte Carlo simulation was used. The experiment was performed on composite thin-walled beams with a square cross-section and six different layer arrangements. To find a relationship between the load and the beam deflection, a digital image correlation (DIC) system was employed. The results, in the form of post-buckling equilibrium paths, were used to validate the proposed approach to conduct a geometrically nonlinear stability analysis. The proposed software together with the Monte Carlo simulation enables a very quick analysis of hundreds of different geometrical imperfections and finding the worst case. The results show that the accuracy of profile manufacturing exerts an influence on the buckling mode and, thus, it can be said that the initial geometrical imperfection together with the buckling mode affect significantly the post-buckling behaviour. A comparison of the results shows that geometrical imperfections have a stronger impact on the post-buckling behaviour of beams than the arrangement of layers.