Composite structures, such as the fiberglass reinforced structure studied in this paper, have been normally treated in previous research as homogeneous anisotropic laminated plates regarding the investigation of their mechanical properties. Throughout this paper, this specific structure is considered in a different way in which the fiberglass and polyethylene matrix are treated separately. By using the proposed method, the material plasticity of polyethylene and the fracture stress of the fiberglass can be taken into account, and thus the fracture of the fiberglass inside the fiberglass reinforced flexible pipes(FGRFP) can be predicted. The mechanical behaviour behavior of FGRFP under two real-life main loadings(tension and internal pressure) is investigated by using analytical and numerical methods based on the proposed technique. Experiments are used to verify the results.

Metallic strip flexible pipes (MSFP), a relatively new style of unbonded flexible pipes, are considered as an attractive alternative to traditional submarine pipes. During its reeling operation, it will inevitably confront various complicated loads, which may affect the integrity and safety of MSFP's utilization. In this paper, the tension-extension and moment-curvature relation of MSFP were obtained by laboratorial tests. The mechanical properties were then imported into the global model established in ABAQUS. The finite element model was adopted to predict the deformation and mechanical responses of MSFP during the operation process. Besides, the effects of reeling length, the diameter of the coiling drum, and the pulling force were discussed. The obtained conclusions will provide some references for optimizing MSFP design and preventing possible damage in the reeling operation.

Fibreglass reinforced flexible pipe (FGRFP) is a kind of composite thermoplastic pipe serving as a preferred application in the field of oil transportation. This paper studies the mechanical behaviour of FGRFPs under pure bending by experimental, numerical and theoretical methods. Full-scale four-point bending tests are conducted and the curvature-bending moment relations of specimens are recorded. In the numerical simulation method (NSM), a detailed finite element model considering both material and geometric nonlinear behaviour is established, and the composite is defined as an orthotropic elastic-plastic material. Based on the Euler–Bernoulli beam theory, a simplified theoretical method (STM) is proposed to predict the ultimate bending moment. In the parametric study, a simple formula is introduced to modify STM to make it more accurate. Good agreements proves the reasonability of the proposed NSM and STM. Additionally, STM could make a contribution to engineers in terms of a concise and relatively accurate way in ultimate status analysis.