Analysis of Surface Damage Formation Mechanism in Milling of CFRPs

Abstract

Carbon fiber reinforced polymer (CFRP) composite has become the preferred material for high level equipment due to its light weight and high strength. A large number of edges, blind windows, profiled contours, etc. are required to be milled after curing in order to manufacture fitting and joining surfaces. However, machining damages such as burrs and tears are easily generated on the surface, which seriously affects the bearing performance of the components. Elucidating the formation mechanism of CFRP surface damage in milling to guide process optimization is the key to achieving high quality machining. Through milling slots in unidirectional CFRP specimens having different fibre orientations, the comprehensive influence mechanism of fiber cutting angle, cutting edge radius and milling cutter movement on the surface damage of CFRP milling is elucidated from two aspects of surface damage distribution and uncut fiber length. It suggests that, fiber cutting angle is a key factor influencing the formation of CFRP surface damage. When it is an acute angle, it is easy to transition from non-damaged state to burr-prone state under the influence of large cutting edge radius. However, the damage distribution at obtuse angles is not affected by cutting edge radius and the surface damage is concentrated between 90° and 135°, which is the coexistence of burr and tear. The milling cutter's movement characteristics cause continuous dynamic change of the fiber cutting angle, which leads to the dynamic accumulation of damage in the easy-to-damage range, and ultimately determine the length of uncut fiber. On this basis, a method for effectively suppressing the surface damage of CFRP trimming is proposed and its effectiveness is verified by experiments, which provides a basis for subsequent studies on the damage suppression.