Study on the drilling performances of a newly developed CFRP/invar co-cured material

Abstract

The CFRP/metal co-cured material which possesses the outstanding properties of both lightweight and high strength has become one of the commonly used materials in the design and manufacture of attitude control flywheel. However, few studies are reported concerning the mechanical drilling operation of this newly developed structural material. To cover the gap and enrich the scientific field of this topic, the present work was performed to specially evaluate the drilling performances of a co-cured material composed of carbon fiber reinforced plastic (CFRP) and invar alloy. The significance of the present work aims to on the one hand, reveal the evolution of vital cutting phenomena including thrust forces, cutting temperatures and surface quality of drilling holes as function of cutting parameters, and on the other hand address the mechanism of controlling the interfacial drilling response. The results indicate that both the thrust forces and cutting temperatures during drilling of the invar phase are relatively higher compared to that of the CFRP phases while it presents elevation for the lower CFRP phase than the upper one due to the effect of chip ejection. The evolution of thrust forces and drilling temperatures present common regularity, in which the feed rate and cutting speed play an essential role, respectively. It is worth noting that the hole size indicates disparities for all the involved layers regardless of the machining parameters, of which the hole size exceeds the nominal diameter for the upper CFRP phase while it presents lower magnitudes for the lower CFRP phase and close gap between the invar phase and expected value. Surface cavity and fiber pullout dominate the hole surface morphology for the upper CFRP phase, matrix degradation and micro-cracks appear on the hole wall of the lower CFRP phase, and chip adhesion and oxidation are the cases for the invar layer. The mechanical effect induces the notch and the thermal effect causes the matrix degradation, which controls the cutting response for the upper and lower interface, respectively.