New analytical approach for buckling of composite sandwich pipes with iso-grid core under uniform external lateral pressure

In this paper, a new analytical approach is developed for buckling of composite sandwich pipes with iso-grid core under uniform external lateral pressure. Firstly, the stiffness contributions of iso-grid cores are evaluated through the new force and moment effect analysis. Then, iso-grid core is transformed into a solid pipe, as the middle layer of the sandwich pipe. The outer, inner, and middle pipes are transformed into an equivalent single-walled pipe. Therefore, composite sandwich pipe with iso-grid core is equalized with a single-walled pipe of the same stiffness. The Rayleigh–Ritz energy method is used to calculate the critical buckling pressure of the composite sandwich pipes with iso-grid cores. The efficiency and accuracy of the presented approach are confirmed by comparing the analytical solutions with finite element results obtained from ABAQUS and other works, showing a good agreement with each other. A parametric study is then carried out to investigate the effect of the scale of the structure, outer and inner pipes ply stacking sequence, radius to total thickness ratio, stiffener to outer and inner pipe thicknesses ratio, and stiffener angle on the buckling of sandwich pipes. Finally, applications of the present approach were demonstrated for designing of tending toward constant various structural applications such as offshore pipelines.