This thesis presents a coherent body of research that advances the science and engineering of asset integrity through improved understanding of material behaviour, interfacial mechanics, and failure processes across a range of materials including composites, polymers, wood, and metals. The work addresses the full asset‑integrity lifecycle - design, assurance, degradation management, and failure investigation - by establishing how micro‑ and nanoscale mechanisms govern the long‑term performance and reliability of structural materials.

A central contribution lies in elucidating the role of interfaces and interphases in determining load transfer, damage initiation, and fracture evolution in polymer‑matrix composites and nano‑modified systems. Through combined surface analysis, micromechanical testing, and multi‑scale modelling, the research quantifies how interfacial architecture controls stiffness, toughness, and pseudo‑ductile behaviour, enabling the design of materials with predictable and optimised failure modes. These insights directly support asset‑integrity objectives by improving confidence in structural performance under variable and extreme service conditions.

Complementary studies develop robust methodologies for failure analysis and integrity assessment, integrating fractography, mechanical characterisation, and environmental degradation modelling. This work provides diagnostic frameworks for identifying root causes of failure in real components, supporting improved inspection regimes, life‑extension decisions, and risk‑based maintenance strategies.

A further strand focuses on sustainable use of materials, including the development of high‑performance cementitious systems and the valorisation of industrial waste streams and biomass with low inherent value. These materials are engineered to deliver enhanced toughness, reduced variability, and improved durability, aligning asset‑integrity requirements with environmental and economic constraints.

Collectively, the submitted publications form a substantial and original contribution to the field of asset integrity. They provide mechanistic understanding, validated methodologies, and practical pathways for designing, assessing, and sustaining reliable engineering assets across their operational life.