Advanced Interface Modeling and Characterization of Thermoplastic Fusion Bonds for Sustainable Structural Applications: An In-Depth Review

In the transition toward the circular economy and high-rate manufacturing, thermoplastic composites (TPCs) are increasingly outperforming conventional thermosets due to their superior fracture toughness, recyclability, and rapid processing capabilities. Among available joining techniques, fusion bonding stands as the main mechanism for structural integration, as it bypasses the fundamental limitations of traditional assembly: the weight penalties and stress concentrations inherent in mechanical fastening, as well as the long cycle times and interfacial weaknesses often associated with adhesive bonding. This paper provides a comprehensive evaluation of welded TPC joints through a dual-methodological approach: a historical narrative review tracing the evolution of fusion bonding principles, and an in-depth literature review of 25 key articles published since 2015. The analysis focuses on the intersection of experimental characterization-quantifying interfacial strength and fracture energy-and numerical modeling techniques, such as Cohesive Zone Modeling (CZM) and progressive damage analysis. By categorizing recent advancements into specific thematic pillars, this study correlates process-induced phenomena with macro-scale mechanical performance and virtual predictive accuracy. The findings synthesize decades of foundational knowledge with cutting-edge research trends, highlighting the transition from empirical testing to computational design. This work serves as a roadmap for achieving standardized, high-performance thermoplastic assemblies in safety-critical applications.