 CFRP/Al7075 Stacking drilling with different point angle drills  Determination of average surface roughness and cutting forces  Investigation of drill point angles effect on delamination Carbon fiber reinforced polymer composite CFRP/Al 7075 are used in the field of military and civil aviation, space industry and many other advanced technology fields. The application CFRP / Al 7075 stacked structure of these two materials is used in aircraft wings, engine components and tail components. In forming this stacked structure, one of the most widely used machining applications is the drilling process. The problems are occurred because of these two materials, which have different chemical and physical properties, in drilling at the same time. These problems occur in the fibers for CFRP material as break, fragmentation, delamination and resin burning. In Al 7075, the problems of chip evacuation and build upedge (BUE) at the main cutting edge are the most important problems. In this respect, the thrust force, moment, chip structure, delamination, average hole surface roughness and tool wear are the problems that need to be considered at the same time. a) b) c) Figure A. After drilling operations a) 120° point angle drill b) CFRP in-hole c) Al 7075 chips Purpose: The main objective of this study is to investigate the drillability of the CFRP/Al 7075 stacked structure with drills with different point angles. Theory and Methods: Experimental studies were performed by drilling 100 holes in each drill under constant cutting (Vc: 50 m/min and f: 0.05mm/rev) parameters. Analysis of variance (ANOVA) was also employed to determine the level of the effect drill point angles for the thrust force and average surface roughness on CFRP and Al 7075. Results: The experimental and statisticall results showed that the drill point angle was the significant variable for the thrust force, moment, delamination and average surface roughness in drilling CFRP/Al 7075 stacked structure. Whereas, the chip forms were not significantly affected by the drill point angle. Conclusion: It was concluded that the point angle of 130 degrees should be the first choice in the drilling of the CFRP/Al 7075 stacked structure.

Bu çalışmada günümüz askeri ve sivil havacılık endüstrisinde yoğun olarak kullanılmakta olan CFRP/Al istifli yapının farklı matkap uç açıları ile delinebilirliği araştırılmıştır. Delme işlemleri 30º helis açılı ve 120º-130º-140º farklı uç açısındaki kaplamasız karbür matkaplar ile doğrudan delme yönteminde, 50m dk-1 sabit kesme hızı, 0.05mm dev-1 ilerleme değerlerinde kesme sıvısı kullanılmadan gerçekleştirilmiştir. Delme işlemleri neticesinde elde edilen F z değerleri ve matkaplardaki aşınmalar incelenmiştir. Kaplamasız karbür matkaplar talaş yapıları bakımından benzer sonuçlar verirken itme kuvveti değerleri 130º uç açılı matkapta daha düşük elde edilmiştir. Daha düşük kuvvetlerde gerçekleşen delme işlemlerinde, matkap aşınmaları da daha az meydana gelmiştir. Çalışma neticesinde kaplamasız karbür 130º uç açılı matkabın doğrudan delme yönteminde CFRP/Al istifli yapının delinmesinde hem takım aşınması hem de F z bakımından 120º ve 140º uç açılı matkaplara kıyasla daha iyi sonuçlar verdiği görülmüştür.