Life Cycle Engineering in Mechanical Assembly: the Role of Additive-Manufactured Reinforcements in Composite-Metal Hybrid Joints

The increasing demand for lightweight materials with high mechanical performance has accelerated the development of hybrid composite-metal joints, especially in the transportation industry. Despite their advantages, these joints often present challenges in terms of manufacturability, reliability, and environmental impact. This study evaluates the environmental performance of composite/metal hybrid joints by comparing two scenarios: with and without penetrative reinforcements produced by Additive Manufacturing (AM). A Life Cycle Assessment (LCA) was conducted in accordance with ISO 14040:2021 and ISO 14044:2021 standards, adopting a cradle-to-gate approach. The functional unit was defined to ensure comparability across both scenarios. Primary data were obtained from experimental setups, while secondary data were sourced from scientific databases such as Ecoinvent. Results indicate that the introduction of AM-based reinforcements leads to an 80% increase in tensile strength, enabling a significant reduction in bonding area. This geometric optimization results in a notable decrease in the environmental burden, particularly in terms of global warming potential. Although AM processes involve high energy inputs and specialized feedstock, the structural benefits achieved allow for a more efficient use of materials. Overall, the study demonstrates that performance-driven design through AM reinforcements can offer a viable pathway toward more sustainable structural solutions.