Functionally Graded Materials by Wire and Arc Additive Manufacturing: Processing Approaches, Applications, and Mechanical Characterisation - a Systematic Review

This research project will conduct a comprehensive systematic review of functionally graded materials (FGMs) produced through wire and arc additive manufacturing (WAAM) and other additive manufacturing (AM) approaches. The primary purpose is to systematically map the current state-of-the-art in FGM development, focusing on material combinations, manufacturing processes, applications, and—most critically—mechanical characterisation methods for spatially varying properties. The review will address three central research questions: (1) From which materials can FGMs be created using AM techniques? (2) How can FGMs be effectively manufactured, with particular emphasis on WAAM for metallic components? (3) What experimental approaches—ranging from classical testing to advanced full-field measurements and inverse identification techniques—will enable accurate determination of spatially dependent mechanical properties? Expected outcomes include a detailed taxonomy of FGM material systems and AM processes, identification of key trends and challenges in WAAM-based FGM production, and a critical evaluation of characterisation methodologies. The project will highlight WAAM's potential for industrial-scale metallic FGMs and demonstrate how coupled full-field kinematics with inverse methods can unlock heterogeneous property mapping. Ultimately, this work will provide researchers and engineers with a roadmap for advancing next-generation FGMs, accelerating their transition from laboratory prototypes to functional structural components.