Investigating delamination, uncut fibers, tolerances and surface topography in high speed Drilling of Polypropylene Composite Reinforced with carbon fibers and calcium carbonate Nano-particles

摘要

Abstract In this study, polypropylene composite reinforced with carbon fibers and calcium carbonate nano-particles is manufactured. Mechanical properties tests showed that composite sample containing nano-particles has 87 more tensile strength, 26 more bending strength and 40 more impact strength than the composite without nano-particles. Then high speed drilling was performed on the composite sample containing nano-particles. After drilling, the holes inlet opening surface was detected for uncut fibers and delamination defects. Dimensional tolerance of the holes inlet opening diameter, holes geometrical tolerances including circularity and cylindricity and also surface topography at the inner wall of the holes were investigated. The amount of uncut carbon fibers has direct relation with feedrate and reverse relation with spindle speed variations. With simultaneous increase of feedrate and spindle speed, uncut fibers are reduced. For each level of feedrate, with increasing spindle speed, the delamination defect decreases. The effect of spindle speed variations on the dimensional tolerance is far larger than the effect of feedrate changes. At low spindle speeds, the effect of feedrate changes on the geometrical tolerance variations is much higher. Optimal dimensional and geometrical tolerances are obtained in condition of the highest spindle speed and lowest feedrate. Although, increasing feedrate at very high levels of spindle speed leads to relative improvement in the drilling tolerances. Drilling with relatively lower feedrates and higher cutting speeds leads to better surface topography at the inner wall of the holes, consequently less surface defects such as cavity, debonding, matrix destroying, fiber pull-out and fiber dust are happened.