Towards sustainability in the aerospace industry: Environmental impact of different drilling strategies for CFRP/Aluminium stacks

In the last decade improving the sustainability of manufacturing processes has become a primary objective to tackle the goals for sustainable development as defined by UN. In this context, the Life Cycle Assessment (LCA) is finding increasing use as a method to measure the environmental impacts of processes and as a tool to support decisions when a choice between different processing routes is required. The present study lies in this context: a detailed LCA analysis has been carried out to compare the environmental footprint of different drilling strategies, the quality of the drilled holes has also been considered to provide reliable guidelines to people interested in drilling operations. In particular, this study investigates the environmental impacts of different drilling strategies applied to CFRP/AA7075-T6 stacks, which are commonly used in structural aerospace assemblies. A cradle-to-gate LCA was performed to compare two main approaches: separate drilling of CFRP laminates and aluminium alloy sheets before their assembly, and one-shot drilling of pre-assembled stacks. A strength of this study, conversely to the others available in the literature, is that the analysis relies on experimental data for energy consumption, drilling forces and hole quality, enabling a high-fidelity environmental assessment. The results show that the drilling strategies significantly affect both the environmental indicators, process performance and hole quality, highlighting a trade-off between energy efficiency and hole characteristics. Findings offer new insight to guide sustainable decision-making in aerospace manufacturing.