Mechanism-Based Degradation and Structural Integrity of Marine Renewable Energy Systems: Multiscale Modelling, Materials Challenges, and Future Qualification Frameworks

Marine renewable energy systems, including offshore wind, tidal, and wave technologies, are central to global decarbonisation strategies but remain constrained by reliability-driven costs and uncertainty in long-term structural performance. Existing qualification approaches are largely based on empirical methodologies and deterministic safety factors that inadequately capture coupled degradation mechanisms operating in harsh offshore environments. This review presents a mechanism-based perspective on structural integrity in marine renewable energy systems by linking microstructure-sensitive deformation and damage processes with engineering-scale reliability assessment. Key degradation mechanisms, including corrosion–fatigue, hydrogen embrittlement, wear, and manufacturing-induced variability, are critically examined together with their interactions across multiple length scales. The review synthesises recent advances in multiscale modelling frameworks spanning crystal plasticity, damage mechanics, fracture mechanics, probabilistic reliability methods, and digital twin technologies. Particular emphasis is placed on the role of manufacturing variability, inspection-informed updating, and hybrid physics–data approaches in improving predictive capability and reducing uncertainty. The review identifies major limitations in current offshore qualification practice, including uncoupled degradation assumptions, insufficient representation of manufacturing effects, and limited integration of monitoring data within lifecycle assessment. Building on these findings, an integrated framework is proposed that combines multiscale modelling, manufacturing-aware qualification, adaptive inspection, and digital twin-enabled updating to support predictive and reliability-informed structural integrity assessment for next-generation marine renewable energy systems.