ABSTRACT Manufacture of modern aircraft components involve production of high value near net-shape carbon fiber reinforced polymer (CFRP) parts, which requires drilling holes for rivets and bolts at acute inclinations. The study explores the surface morphology of the inclined holes (30 ͦ, 60 ͦ, and 90 ͦ) drilled in CFRP under cryogenic cooling using coated carbide tools. Inclined hole drilling performance was measured using machining forces, surface finish, and bore integrity. It has been shown that cryogenic machining of acutely inclined small diameter holes generated at least 40% higher thrust forces compared to dry cutting. Surface quality under cryogenic was enhanced than dry cutting with reduced matrix transverse cracking that helped suppress the fiber debonding and pull out. This mechanism also aids to minimize stress concentration regions along matrix/fiber interfaces due to promotion of fracture mode II in-plane sliding shear of carbon fibers and reduction of fracture mode III out of plane peel-up and push-down interlaminar delamination. Effect of tool coating on bore surface integrity showed that double coat TiN tool with a point angle of 140 ͦ generated at least 40% lower thrust forces than Physical Vapor Deposition (PVD)-coated multilayer TiAlN flat bottom drill during cryogenic-assisted drilling.

中文翻译：

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深冷环境加工CFRP斜孔表面形貌

摘要 现代飞机部件的制造涉及高价值的近净形碳纤维增强聚合物 (CFRP) 部件的生产，这需要在锐角处为铆钉和螺栓钻孔。该研究探索了使用涂层硬质合金刀具在低温冷却下在 CFRP 中钻出的斜孔（30 ͦ、60 ͦ 和 90 ͦ）的表面形态。斜孔钻削性能使用加工力、表面光洁度和钻孔完整性进行测量。已经表明，与干切削相比，锐角小直径孔的低温加工产生的推力至少高出 40%。与干切割相比，低温下的表面质量提高了，减少了基体横向裂纹，有助于抑制纤维脱粘和拉出。由于促进了碳纤维的断裂模式 II 面内滑动剪切和减少了断裂模式 III 平面外剥离和下推层间分层，该机制还有助于使沿基体/纤维界面的应力集中区域最小化。刀具涂层对孔表面完整性的影响表明，在低温辅助钻孔过程中，与物理气相沉积 (PVD) 涂层多层 TiAlN 平底钻相比，具有 140 ͦ 尖角的双层涂层 TiN 刀具产生的推力至少低 40%。