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<p>The assembly of current aircraft structures, such as wing boxes and fuselage sections, relies heavily on mechanical fastening, requiring thousands of holes to be drilled into composite components. With rising demand for commercial single-aisle aircraft, optimizing drilling and assembly processes has become critical. However, drilling carbon fibre–reinforced polymer (CFRP) laminates remains challenging due to their anisotropic, inhomogeneous structure and the abrasiveness of carbon fibres. These factors often result in machining defects, with push-out (exit) delamination being particularly detrimental, as it compromises structural integrity. In this sense, this study presents an experimental methodology for in-process monitoring and characterizing drilling-induced defects in aerospace-grade unidirectional CFRP. A confocal 3D measurement system and a custom MATLAB algorithm were developed for automatic defect detection, including delamination and uncut fibres. Drilling tests were conducted over 70 holes using a carbide twist drill. In terms of process monitoring, three indicators were evaluated: mean thrust force (<i>F</i><sub>mean</sub>), entry/exit force gradient difference, and exit energy (<i>E</i><sub>exit</sub>). Among them, <i>E</i><sub>exit</sub> demonstrated the strongest correlation with defect severity, capturing a significant increase in delamination factors after 45 holes. Therefore, the proposed methodology offers a robust framework for reducing critical drilling defects, improving part quality, minimizing rework and rejection, and contributing to the development of autonomous, non-assisted manufacturing systems in the aerospace industry.</p>

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CFRP drilling–induced defect investigation: part quality characterization and process monitoring approach

  • 期刊论文

  • 发表日期：

    2025年7月18日

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  • Iker Urresti-Espilla,
  • Martin Telleria,
  • Iñigo Llanos,
  • Luis Norberto López de Lacalle

摘要

The assembly of current aircraft structures, such as wing boxes and fuselage sections, relies heavily on mechanical fastening, requiring thousands of holes to be drilled into composite components. With rising demand for commercial single-aisle aircraft, optimizing drilling and assembly processes has become critical. However, drilling carbon fibre–reinforced polymer (CFRP) laminates remains challenging due to their anisotropic, inhomogeneous structure and the abrasiveness of carbon fibres. These factors often result in machining defects, with push-out (exit) delamination being particularly detrimental, as it compromises structural integrity. In this sense, this study presents an experimental methodology for in-process monitoring and characterizing drilling-induced defects in aerospace-grade unidirectional CFRP. A confocal 3D measurement system and a custom MATLAB algorithm were developed for automatic defect detection, including delamination and uncut fibres. Drilling tests were conducted over 70 holes using a carbide twist drill. In terms of process monitoring, three indicators were evaluated: mean thrust force (Fmean), entry/exit force gradient difference, and exit energy (Eexit). Among them, Eexit demonstrated the strongest correlation with defect severity, capturing a significant increase in delamination factors after 45 holes. Therefore, the proposed methodology offers a robust framework for reducing critical drilling defects, improving part quality, minimizing rework and rejection, and contributing to the development of autonomous, non-assisted manufacturing systems in the aerospace industry.