Comparison of buckling of an arched, rubber-core sandwich composite panel to finite element modeling

Finite element modeling was developed for buckling of an unbalanced fiberglass–rubber sandwich composite panels under hydrostatic pressure. The analysis was verified with tests on two sets of full-scale panels with different rubber cores. The model was composed of solid elements for the core, and shell elements with a neutral axis offset for the skins. An accurate description of the nonlinear rubber at strains <5% was crucial. The buckling pressures predicted by the model were 148 ± 7 and 323 ± 24 kPa for the two sets of panels, which agreed well with the measured values of 147 ± 2 and 317 ± 7 kPa, respectively. At low pressure, there was agreement of deflections and strains from the model to the measurement, but at high pressure the agreement was unsatisfactory. A secondary elastic instability was observed, occurring more suddenly in the model. The differences were ascribed to the lack of inclusion of defects in the model.