阶梯钻钻削CFRP锥形沉头孔实验研究

Experimental Study on Stepped Drilling Tapered Countersunk Hole Of CFRP

碳纤维增强复合材料(CFRP)被广泛应用于航空航天、轨道交通等领域。CFRP零件经常通过螺栓与其它零件联接,但是由于CFRP层间强度低,在钻孔过程中容易产生分层、纤维拉出、基体损伤等缺陷。对于锥形沉头孔来说,其锥面加工质量更难保证。文章建立了锥形沉头孔的加工数学模型,研究了沉头锥面缺陷的形成机理;通过实验研究了CFRP锥形沉头孔的加工质量,分析了加工过程中的轴向力、温度的变化规律;采用扫描电镜分析了锥形沉头的孔壁表面特征。结果表明,在沉头锥面上CFRP在层间发生了严重的分层现象,在层内发生了明显的块状断裂,在孔壁锥面和直面过渡区发生了纤维撕裂。通过研究发现,通过改变主轴转速可以提高锥面和过渡区的加工质量。

CFRP is widely used in aerospace,rail transportation and other fields.CFRP parts are often connected to other parts by bolts,but due to the low interlayer strength of CFRP,defects such as delamination,fiber pullout,and matrix damage are prone to occur during the drilling process.For tapered countersunk holes,the machining quality of the tapered surface is more difficult to guarantee.In this paper,a mathematical model for machining the countersink hole is established,and the formation mechanism of the countersunk cone defect is studied.The machining quality of the tapered countersink hole of CFRP was studied experimentally,and the changes of the axial force and temperature during processing were analyzed.The surface characteristics of the hole wall of the tapered countersink were analyzed by sem.The results showed that the CFRP had severe delamination between the layers on the countersunk cone surface,obvious block fractures occurred in the layer,and fiber tearing occurred in the transition zone between the cone wall and the straight surface of the hole wall.It is found through research that the machining quality of the taper surface and the transition zone can be improved by changing the spindle speed.