Limit strength and reeling effects of sandwich pipes with bonded layers

Sandwich pipes composed of two steel layers separated by a polypropylene annular can be used for deepwater oil and gas transportation, combining high structural resistance with thermal insulation in order to prevent paraffin and hydrates formation. In this work, sandwich pipes with typical inner diameters of those employed in the offshore production are analyzed numerically regarding to the influence of the inter-layer adhesion between steel and polymer on the ultimate strength under external pressure and longitudinal bending. The effect of the reeling method of installation is also simulated. The maximum shear stress of the metal–polymer interface is obtained by experimental tests. Numerical simulation of the adhesion is modeled by contact surfaces adopting a maximum shear stress value to allow the relative displacement between the layers. It was observed that the ultimate strength of the sandwich pipe is strongly dependent on the shear stress acting at the interface.