Sustainable Marine Structures

Systematic Review of Functionally Graded Pipelines and Proposal of a New Material Property Variation to Enhance Operational Stability

Frederick Ebili

Department of Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, Glasgow G4 0LZ, UK Metallurgical Raw Materials Development and Investment Promotion Department, Federal Ministry of Steel Development, Abuja P.M.B 107, Nigeria

Selda Oterkus

University of Strathclyde

Erkan Oterkus

Department of Naval Architecture, Ocean and Marine Engineering, University of Strathclyde, Glasgow G4 0LZ, UK 

DOI: https://doi.org/10.36956/sms.v7i4.2726

Received: 12 September 2025; Published: 16 December 2025

Abstract

The global discussion surrounding Functionally Graded Materials (FGMs) highlights their unique and diverse micro-material properties that result from varying two or more materials in a strategic combination profile. These combinations produce distinct physical and chemical characteristics. Changes in these characteristics may occur continuously, referred to as a gradient function, or discontinuously as a stepwise function. The changes can appear within homogeneous or heterogeneous material geometries. The variation in material properties depends on the volume fraction index function. This variation can occur in 1D, 2D, or 3D, either in the thickness or length direction within a material model. The vacuum in the review study on mechanically toughened and thermally resistant Functionally Graded (FG) pipelines prompted the current review study. This study addresses the absence of an appropriate variational function for FG cylindrical pipelines. It proposes a gradation function pattern to improve pipeline structural performance. An appraisal based on relevant FGM literature was conducted to improve the temperature differentials in traditional composite materials and stress-related issues in carbon steel pipelines. The review identifies specific FGM property variations that reduce failures that are possible in conventional materials. Reviewed articles and evaluation procedures followed the 2020 PRISMA guidelines. Literature was obtained from Scopus, Connected Papers, and other reputable sources. The study also discusses potential FG pipelines for gas and green energy transportation. The reviewed literature establishes the context for this research and addresses the gap in 3D FG model variation functions involving multiple materials.

Keywords: FGMs, Volume Fraction Index, Pipeline, Homogenous Material, Continuum, Stepwise

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