Influence of autoclaving process on the stability of thin-walled, composite columns with a square cross-section - Experimental and numerical studies

Stability of thin-walled, composite, aerospace structures is a key issue in an analysis of its safety. This research aims to investigate the influence of the curing parameters on the stability (buckling behaviour) of thin-walled, GFRP laminates. Under inspection was taken the compression of eight-layered (layup [45/-45/45/-45]s), composite columns with a square cross-section with the dimensions: (width x height x thickness) 80 mm x 80 mm x 1.2 mm and length equal to 240 mm. The composite was cured in two autoclaving curing cycles. The first is a nominal curing cycle on an empty aluminium mandrel, while the second is a modified curing cycle on a full aluminium mandrel. To verify the quality of the manufactured composite, an assessment of the microstructure has been performed. Then, compression tests were performed and two FE models were pre pared, with and without the inclusion of residual stresses in the material. Additionally, for the purpose of the second FE model, coefficients of thermal expansion of the laminate were determined experimentally. A comparison of FE models with experimental data leads to the conclusion that residual stresses are not negligible and must be taken into account FE modelling of columns with closed cross-section.