A comprehensive review of failures in bi-material interfaces: Mechanisms, prediction, and mitigation strategies

Bi-material systems are increasingly vital in aerospace, automotive, microelectronics, and biomedical engineering due to their capacity to integrate complementary material properties, such as high strength-to-weight ratios, customized thermal insulation, and targeted biocompatibility, that monolithic materials cannot achieve. Despite these advantages, the operational integrity of bi-layer architectures is frequently compromised by interfacial failure modes driven by mismatched elastic moduli, coefficients of thermal expansion (CTE), and processing-induced residual stresses. These vulnerabilities often manifest as delamination, fatigue cracking, or environmental degradation, leading to premature structural failure. While recent research has explored isolated material pairs or specific mechanisms, a holistic synthesis that bridges fundamental mechanics across diverse sectors is currently absent. This review addresses this critical gap by providing a comprehensive, multi-disciplinary examination of bi-material interfaces. We categorize prevalent failure origins, from thermo-mechanical stress concentrations to hygrothermal aging, and provide an evaluative framework for mechanical predictive methodologies, including Linear Elastic Fracture Mechanics (LEFM), Cohesive Zone Modeling (CZM), and Phase-Field Modeling (PFM). Furthermore, we assess state-of-the-art mitigation strategies, such as functionally graded interlayers, bio-inspired interlocking geometries, and advanced surface functionalization. By unifying experimental observations with computational frameworks, this work establishes a strategic roadmap for optimizing interfacial performance, offering researchers and practitioners a definitive guide to designing resilient, next-generation bi-material systems for high-performance applications.