Design, fabrication and stiffness analysis of a novel GFRP sandwiched pipe with stiffened core

Glass fibre reinforced polymer (GFRP) pipelines are widely used in civil and offshore engineering owing to their good mechanical performance and light weight. However, typical structural problems, such as low radial stiffness, are still existing in the GFRP pipelines. In this paper, a novel GFRP sandwiched pipeline structure with a stiffened core was designed and was integrally fabricated by a newly developed multistage filament winding (MFW) technique. The radial stiffness of the GFRP stiffened pipe was investigated through a combination of theoretical, numerical and experimental methods. It was found the structural layer formed by GFRP webs combined with foam blocks effectively increase the stiffness with a considerable weight reduction for the newly proposed pipe structure. In addition, the mechanical behaviour of the stiffened pipe was precisely predicted by the adopted theoretical method and the proposed numerical model. Based on the validated model, the structural stability under confined load of the GFRP stiffened pipe was numerically studied and the failure map was constructed as a function of the related geometric parameters. The results provided a new concept for the pipeline structural design and a guidance for the geometric optimization of the proposed pipeline configuration.