Characterization of friction properties at the workmaterial/cutting tool interface during the machining of randomly structured carbon fibers reinforced polymer with carbide tools under dry conditions

Abstract

Carbon fiber reinforced polymers (CFRP) are increasingly employed within the aerospace industry, particularly within the aircraft sector. However, machining of fiber reinforced composites can be quite complex, first due to the inherent heterogeneity resulting from the reinforcements/matrix assembly and second due to the presence of high modulus/high strength fibers. Therefore, a lot of Finite Element models have been developed in order to understand their material removal mechanisms. Among the scientific issues faced by these works, the identification of friction coefficients between CFRP and cutting tool materials remains a strategic field of research. This paper aims at characterizing the friction properties between composite and cutting tool materials. More precisely, the paper focuses on the context of a randomly structured CFRP, called HEXTOOL™, machined with a carbide tool under dry conditions. The specific tribological conditions during machining of such heterogeneous materials are discussed in the paper, especially the configuration of the tribosystem (‘opened tribosystem’). The great lack of friction coefficient is mainly due to the absence of relevant tribometers simulating the tribological conditions occurring in cutting. This paper presents the development of a new tribometer designed to simulate conditions corresponding to machining of randomly structured CFRP materials. It provides quantitative values of friction coefficient and heat partition coefficient depending on sliding velocities. This work has revealed that friction coefficients are very low in dry regime compared to those obtained in metal cutting. Moreover, experimental results confirm that friction coefficient decreases from 0.25 to 0.1 when sliding velocity increases. Finally this works establishes that a TiN layer deposited on carbide tools is not able to modify friction properties.