Elasticity analysis of sandwich pipes with functionally graded interlayers

• Sandwich pipes under internal and/or external pressure are considered.
• Functionally graded interlayers are proposed to improve adhesion at interface in sandwich pipe.
• Closed-form analytical solutions are determined and comparative analyses performed.
• Investigation permit us to improve sandwich pipe design in severe application fields.

Sandwich pipes that combine structural performance with thermal insulation in their design are viewed as a light-weight alternative to pipe-in-pipe systems, in which the core material is used only for thermal insulation purposes. Incorporating functionally graded interlayers into the sandwich pipe design may help improve adhesion at the interfaces between the core layer and inner and outer pipes which has been identified as one of the major factors affecting sandwich pipe performance. In this paper, sandwich pipes with two thin functionally graded interlayers between the core layer and inner/outer pipes are investigated in the context of elasticity theory. Closed form analytical solutions are derived for stresses and displacements in the pipes subjected to internal and/or external pressure. Comparative analysis of sandwich pipes with and without functionally graded interlayers is performed and beneficial effect of graded interlayers on stresses and displacements in the pipe is established.