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.