High-strength carbon fiber reinforced polymer (CFRP) composites have become popular materials to be utilized in the aerospace and automotive industries, due to their unique and superior mechanical properties. An understanding of cutting temperatures is rather important when dealing with high-strength CFRPs, since machining defects are likely to occur because of high temperatures (especially in the semi-closed drilling process). The friction behavior at the flank tool-workpiece interface when drilling CFRPs plays a vital role in the heat generation, which still remains poorly understood. The aim of this paper is to address the friction-induced heat based on two specially-designed tribometers to simulate different sliding velocities, similar to those occurring along the flank tool-work interface in drilling. The elastic recovery effect during the drilling process was considered during the tribo-drilling experiments. The drilling temperatures were calculated by the analytical model and verified by the in-situ experimental results gained using the embedded thermocouples into the drills. The results indicate that the magnitudes of the interfacial friction coefficients between the cemented carbide tool and the CFRP specimen are within the range between 0.135–0.168 under the examined conditions. Additionally, the friction caused by the plastic deformation and elastic recovery effects plays a dominant role when the sliding velocity increases. The findings in this paper point out the impact of the friction-induced heat and cutting parameters on the overall drilling temperature.

The honeycomb sandwich structure has been widely used in the aerospace industry due to its high specific strength and stiffness. However, the machining defects of the aluminum honeycomb core (AHC) have become the key factor that restricts its application. In this paper, the defects' characteristics including the formation mechanism, distribution characteristic, and cutting process of honeycomb cell walls during AHC milling process were experimentally investigated. Furthermore, using normalized Cockcroft and Latham ductile fracture criterion and Johnson–Cook (JC) constitutive model, the numerical simulation of the AHC machining process was conducted concerning the entrance angle. It is indicated that six categories of milling defects are obtained and the quantity as well as distribution regularity of AHC milling defects are determined by the double effects of both the entrance angle and cutting force. Most of the surface defects of honeycomb materials were found concentrated in three regions, named by zones I–III, in which extruding, shear, and tensile deformation was mainly generated, respectively. Besides, the finite element simulation results also agree well with the experimental findings. Finally, a novel optimization method to avoid defects in the aforementioned regions by controlling the entrance angle of all the honeycomb walls during the cutting process was proposed in this paper. Meanwhile, the optimal control equations of the entrance angle for all cell walls were derived. This method was verified by milling experiments at last and the results showed that the optimization effect was obvious since the quality of the machined surface was greatly improved.

The new developed metal/composite co-cured material composed of carbon fiber–reinforced plastic and Al phases has been increasingly applied for manufacturing of attitude control flywheel in aerospace industry. However, drilling of co-cured material is still a challenging task to produce holes with high quality and low cost in the assembly chain and dynamic balance debugging of attitude control flywheel. In other words, the relevant mechanisms and experimental findings involved in the drilling process of carbon fiber–reinforced plastic/Al co-cured material is not clearly defined, which impedes the progress of attitude control flywheel production. To this end, this article specially addresses the experimental studies on the drilling process of carbon fiber–reinforced plastic/Al co-cured material with standard TiAlN-coated cemented carbide twist drill. The significance of this work aims to reveal the regardful cutting responses of the hole characteristics and tool wear modes during the practical drilling process of co-cured material. A full factorial experiment including three levels of feed rate and four levels of cutting speed was performed. The hole diameter shows different values in different positions while it indicates consistent pattern regardless of the cutting variables: the largest in the Al phase, followed by the upper and lower carbon fiber–reinforced plastic phases, respectively. Grooves and matrix degradation are the major machining defects for carbon fiber–reinforced plastic layers, while a great chip debris adhered to the machined surface is the case for Al layer. Subsequent wear analysis showed that abrasion was mainly maintained at the vicinity of major/minor cutting edges and drill edge corner, followed by chip adhesion on the chisel edge region. Carbide substrate of drill flank face is exposed, and thereafter cavities are formed under the strong mechanical abrasion. These results could provide several implications for industrial manufacturers during the attitude control flywheel production.

The milling of thin-walled workpieces is a common process in many industries. However, the machining defects are easy to occur due to the vibration and/or deformation induced by the poor stiffness of the thin structures, particularly when side milling the edges of plates. To this problem, an attempt by inclining the tool to a proper tilt angle in milling the edges of plates was proposed in this paper, in order to decrease the cutting force component along the direction of the lowest stiffness of the plates, and therefore to mitigate the machining vibration and improve the machined surface quality effectively. First, the milling force model in consideration of the undeformed chip thickness and the tool-workpiece engagement (TWE) was introduced in detail. Then, a new analytical assessment model based on the precisely established cutting force model was developed so as to obtain the optimum tool tilt angle for the minimum force-induced defects after the operation. Finally, the reliability and correctness of the theoretical force model and the proposed assessment model were validated by experiments. The methodology in this paper could provide practical guidance for achieving high-quality machined surface in the milling operation of thin-walled workpieces.

Side milling thin-walled workpiece edges is an indispensible procedure in the continuous process chains for the high-efficiency machining of thin-walled functional parts, for example, the small- and medium-sized compressor blades. In these operation cases, the workpiece vibration is easy to occur due to the poor stiffness of the thin-walled structures, causing defects to the machined surface finish and even the dimensional accuracy of the thin-walled workpiece edges. To this problem, this study proposes the tool inclination method based on the adaption of the cutting force component in the lowest stiffness direction of the thin-walled workpiece, and it aims, first, to guarantee the machined surface finish which is mostly dominated by the workpiece vibrations mainly induced by the relatively high cutting forces and, second, to guarantee the high machining efficiency. The parametric study on the tool inclination angle for side milling the thin-walled workpiece edges was conducted by using the finite element simulations. First, the finite element models were elaborated and validated by the experimental results in terms of the cutting forces. Then, based on a series of finite element simulations, the effects of the tool inclination angle on the cutting forces adaption and its corresponding mechanism, that is, the chip formation variation, were investigated. Simulation results under the given conditions showed that the optimal tool inclination angle for the minimum absolute value of F_n was 26°. At last, the prediction feasibility for the best machined surface finish when side milling the low-stiffness thin-walled workpiece edges at the optimal tool inclination angle was well validated by the experimental results. The proposed tool inclination method with the solid end mill based on the finite element model to improve the machined surface finish is meaningful and feasible for the high-efficiency manufacturing processes of thin-walled workpieces.

With the advancement of high-end manufacturing, the application of difficult-to-machine materials such as titanium alloys and superalloys is becoming increasingly widespread. Their inherent material properties pose challenges during machining, including high cutting temperatures, rapid tool wear, and difficulty in controlling surface quality. Nanofluid minimum quantity lubrication (NFMQL) technology, as an advanced lubrication and cooling method, enhances the thermal conductivity and lubricating properties of fluids by uniformly dispersing nanoparticles in the base oil. This paper reviews the preparation methods, advanced atomization techniques, and core mechanisms of NFMQL technology. It focuses on analyzing the effectiveness of this technology in four major machining processes, turning, milling, grinding, and drilling, for typical materials such as titanium alloys, steel, and superalloys. Compared to dry cutting, conventional MQL, and poured cooling, NFMQL reduces cutting forces/torque, cutting temperatures, tool wear, and surface roughness while improving material removal rates, machining accuracy, and surface integrity. This paper concludes by summarizing the technology’s advantages, current challenges, and future research directions.