Numerical study of interface damage formation mechanisms in machining CFRP/Ti6Al4V stacks under different cutting sequence strategies

Composite/titanium stacks are extremely difficult to machine due to the generation of severe interface damage, being the critical defect to suppress. The present paper aims to use the finite element method (FEM) to investigate the interface damage formation mechanisms following the machining of CFRP/Ti6Al4V stacks with a particular focus on the distribution of stresses and temperatures. Its key objective lies in revealing the effects of different cutting sequence strategies on the interface damage formation to guide the design of the stack machining processes as well as the selection of cutting sequences. A micro-mechanical orthogonal cutting model and a 3D drilling model of the CFRP/Ti6Al4V stacks were developed to explore the fundamental cutting edge/material interactions and the damage formation mechanisms under both the CFRP → Ti and Ti → CFRP strategies. The investigations confirm the dominant impact of the cutting sequence strategy on the stress and temperature distribution during the machining of CFRP/Ti stacks, which is mainly responsible for the diverse interface damage. Besides, the interface damage of a material layer becomes more serious when the material is machined as a secondary phase due to the adhesion and abrasion of previous material chips. The coupling effects of the matrix damage and the interface bending are the influential factors leading to severe interface damage under the Ti → CFRP strategy, thereby unfavorable for the interface quality.