Surface Roughness after Milling of the Al/CFRP Stacks with a Diamond Tool

Hybrid sandwich structures are increasingly used in aerospace and automotive industries due to their high strength-to-weight ratios. However, the surface quality after machining these materials remains a challenge. Prior research has shown that different layers in a composite sandwich may respond differently to machining parameters. No prior work had resolved how feed rate and milling strategy specifically affect surface roughness and topography in Al/CFRP stacks. This gap motivated the need for a focused study on the effects of machining conditions on surface characteristics. Understanding these effects is crucial for optimizing manufacturing processes. The study aims to clarify how surface roughness parameters vary with material type and machining conditions. The goal is to identify optimal settings that minimize surface irregularities. This contributes to the broader field of precision machining of hybrid materials.

The study aimed to evaluate how feed rate and milling strategy influence surface roughness and topography in Al/CFRP hybrid structures. The specific problem addressed is the variability in surface quality between the metal and composite layers. The motivation comes from the need to improve machining precision in multi-material components. The researchers sought to determine which parameters most significantly affect surface characteristics. They focused on Ra, Rz, Sp, Sz, and Sv as key indicators. The study also aimed to establish how these parameters differ between the two layers. The goal was to provide a basis for optimizing machining technology. This could help reduce surface irregularities in hybrid structures.

The study used a diamond blade tool to mill hybrid structures made of Al 2024 and CFRP. Surface roughness and topography were measured using Ra, Rz, Sp, Sz, and Sv parameters. The samples were processed under varying feed rates and milling strategies. The researchers analyzed the resulting surface patterns using 3D profilometry. Statistical methods were applied to assess the significance of each parameter. The metal and composite layers were evaluated separately. The team compared the effects of feed rate and milling strategy on each layer. The data was used to determine optimal machining conditions.

The lowest Ra and Rz values were found on the Al 2024 surface, while the highest were on the CFRP surface. The same trend was observed for Sp, Sz, and Sv parameters, with exceptions noted for Sp. The metal layer showed smoother surfaces compared to the composite layer. A periodic pattern of micro-irregularities was observed in most samples. Statistical analysis confirmed that feed rate alone affected the metal layer. For CFRP, both feed rate and the S × f_z interaction were significant. The highest Sp value was recorded on the CFRP surface. These results highlight the material-dependent effects of machining parameters.

The study shows that surface roughness and topography vary significantly between Al and CFRP layers. The metal layer is less affected by milling strategy than the composite layer. Feed rate plays a major role in determining surface quality for both materials. The interaction between strategy and feed rate is especially important for CFRP. The periodic micro-irregularities suggest a consistent machining effect. These findings help in selecting optimal machining conditions. The results support the design of processing technology for hybrid structures. The authors propose that these insights can guide future machining practices.