Study on grinding removal mechanism and subsurface damage of bionic layered graphene ceramic matrix composites

Abstract

Bionic layered graphene ceramic matrix composites have excellent properties of high strength, high toughness and heat resistance, and are important materials for national defense equipment, but they are also typical brittle and difficult-to-machine materials. To achieve high quality and low damage machining of the composite parts, grinding removal mechanism and subsurface damage are investigated in this paper. Firstly, the SPH simulation models for indentation and scratching of a single diamond grain are established. The effect of addition of graphene nanosheets on the crack expansion mechanism and subsurface damage is investigated. Then, the simulation models of different angles of graphene nanosheets are established to analyze the effect of graphene anisotropy on grinding process of composites. Finally, the grinding removal mechanism of the composites is investigated by analysing crack expansion and removal forms of the composites at different scratching velocities and depths. The results show that incorporation of graphene nanosheets can reduce subsurface damage of composites and provide a certain shielding effect on the cracks. The optimal effects for reducing subsurface damage and cracks are obtained when graphene nanosheets angle is 0°. As scratching depth increases, the material removal mode gradually changes from plastic removal to brittle removal, and subsurface damage and crack depths also increases. The increase in scratching velocity leads to a subsequent increase in material strain rate, which inhibits crack generation and reduces subsurface damage depth. The form of material removal and crack generation in scratching experiments is consistent with the simulation analysis when changing the scratching depth. Furthermore, the effect of graphene nanosheets on crack deflection corresponds with the simulation results. This study can provide an important theoretical basis for the grinding process of bionic layered graphene ceramic matrix composite parts.