基于划痕试验的碳纤维/环氧树脂复合材料制孔毛刺与撕裂缺陷形成机制

碳纤维/环氧树脂（C/EP）复合材料制孔毛刺和撕裂缺陷，对构件的装配精度影响较大。为了揭示C/EP复合材料制孔毛刺和撕裂缺陷的形成机制，采用微米划痕试验研究沿不同纤维方向切削加工时材料的破坏去除过程，并用FEI公司Quanta 200 环境扫描电镜对划切后的沟槽及切屑的形貌进行观察分析。结果表明：当划切方向与纤维方向垂直时，划切力最大，较易产生撕裂缺陷；当划切方向与纤维方向呈30°、45°和60°时，划痕左侧纤维受到压头挤压向左退让并弯曲，产生锯齿形断裂，否则形成毛刺；划痕右侧纤维为避让压头发生较大的弯曲变形，纤维断裂均匀，不容易形成毛刺。理论分析和划痕试验结果表明：制孔加工时，纤维方向与刀具旋转方向成钝角的区域容易产生毛刺缺陷，与刀具旋转方向成锐角的区域边缘光滑，与刀具旋转方向垂直的区域容易形成撕裂缺陷；出口缺陷与试验结果一致。

Burr and spalling damages formation mechanism of carbon/epoxy composites by scratching experiment

Burr and spalling damages introduced by drilling have great influence on the assembling accuracy of carbon/epoxy(C/EP) composite components. In order to investigate the formation mechanisms of burr and spalling, scratching experiment was adopted to study the fracture and removal process of C/EP composites cutting with different fiber orientations. Chips and scratching grooves were observed by FEI Quanta 200 environmental SEM. Results show that when scratching direction is perpendicular to fiber orientation, scratching force is the largest and spalling is prone to appear. When the angle between scratching direction and fiber orientation is 30°, 45°, and 60°, the fibers on the left side of groove yield towards the left, bend and fracture in the zigzag shape, otherwise they form burr damage. While the fibers on the right side of groove bend in a large deformation and fracture homogenously, are not easy to form burr. Theoretical analyses and scratching experimental results show: burr is prone to appear in the region where the included angle between fiber orientation and cutting speed direction is acute. Hole exit edge is smooth in the region where the included angle between fiber orientation and cutting speed direction is obtuse. Spalling is prone to appear where fiber orientation is perpendicular to cutting speed direction. The above distribution is in accordance with the experimental results.