Multi-scale machining damages of CFRP circular cell honeycomb during end face machining

Abstract

CFRP circular cell honeycomb is becoming increasingly important in aerospace due to its low density, high specific stiffness, impact resistance and microwave absorption performance. However, high-quality machining of CFRP circular cell honeycomb still represents a significant challenge due to its anisotropic, heterogeneity and discontinuous characteristics. This paper is presented to summarize the machining damage and analyze its cause. In this paper, the exit angle and MRR are defined to describe the effect of discontinuous structure on material removal process, the machining damage of CFRP circular cell honeycomb is classified based on the morphology and scale, the end face machining experiments are carried out to study the effect of machining method (milling and grinding), geometry of tools, exit angle and MRR on damage. The results show that milling produces larger tearing and less burr than grinding. The exit angle influences the curvature radius of fiber that determines fiber fracturing significantly, and side face burr occurs as exit angle and curvature radius of fiber increases. The MRR is larger in cut in and cut out stage of circular cell, tearing and delamination occurs respectively, but the chamfer or fillet of the grinding wheel tetrad material removal process and strength the stiffness of machining area, damage was suppressed. Considering the frequency and the size of damage may occur systematically, grinding wheel with chamfer or fillet is recommended to process CFRP circular cell honeycomb.