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Cutting force plays an important role in the analysis of machining dynamics. In trimming of thin-walled structures, the stick-out length of the workpiece is very large when compared with the traditional milling process, which may result in a large vibration velocity along the tool axis. Since the amplitude of the vibration velocity of the workpiece is comparable to that of the tool velocity caused by the rotary motion of the spindle, it affects the relative velocity between the tool and the workpiece, making the trimming process an oblique cutting process with a time-varying inclination angle, instead of a constant value β , the helix angle of the tool. To this end, we developed a dynamic cutting force model to investigate this effect, and compared simulated and dynamometer-measured cutting forces to validate the established model. The results show that the vibration velocity of the workpiece in the trimming process has a modulating effect on cutting forces, which can significantly reduce the amplitude of the cutting force along the tool axis. [ABSTRACT FROM AUTHOR]

Thermal loading of fiber reinforced composites during traditional machining is inevitable. This is due to the fact that most of the mechanical energy utilized in material removal is converted into heat, which is subsequently dissipated into the workpiece, the cutter and is carried away by the chips. Heat conduction into the workpiece might cause thermal damage if the generated temperatures exceeded the glass transition temperature of the epoxy matrix. In this work, the amount of heat flux applied to the machined edge and the temperature distribution in a multidirectional GFRP composite laminate was determined using an inverse heat conduction method. The spindle electric power, cutting forces and boundary temperatures on the workpiece were measured during edge trimming of the GFRP laminate with a PCD cutter at different spindle and feed speeds. The transient heat conduction problem in the laminate was simulated using the finite element method and the amount of heat flux conducted through the machined surface was determined. It was found that the heat flux conducted to the workpiece represented only a small fraction of the total heat and is more influenced by the feed speed than the spindle speed. The temperature of the machined surface was found to be lower than the glass transition temperature of epoxy for all cutting conditions tried in this study. [ABSTRACT FROM AUTHOR]

Edge trimming of CFRP composite laminates, using abrasive tools, is needed as a finishing operation for better quality and dimensional accuracy. Fiber delamination and resin burning are the major difficulties associated with traditional machining processes of CFRP. Although dry cutting is preferable for cutting CFRP which not absorb cutting fluid and eliminate the need for subsequent cleaning, increasing cutting temperature leads to degradation, smearing, and burning of epoxy resin. This paper investigates the effect of different fluid delivery methods (MQL/flood) on ultrasonic assisted machining (UAM) of multidirectional CFRP laminates using diamond abrasive tools at different cutting conditions. The process parameters studied were cutting speed, feed rate, radial depth of cut, and cooling modes. Cutting forces, surface integrity, and bouncing-back effect were the output responses of this study. Statistical analysis was conducted to study the effect of each factor on the performance characteristics. The results showed that flood coolant provide better results than MQL. However, MQL responses still comparable with flood coolant. The conditions that gave the best responses of MQL were determined which can be utilized for near dry cutting demands. [ABSTRACT FROM AUTHOR]

2D and 3D finite element models were developed to simulate the machining of CFRP with different levels of tool wear. Models were validated by edge trimming experiments on a uni-directional laminate at different fibre orientations using a three flute PCD milling tool. MSC Marc was used to develop the model and in conjunction with a Hashin damage material model. Modelling results are validated according to measured cutting forces at different cutting speeds and feed rates. A percentage difference of +10% and +5% was calculated for the 3D model for Fx and Fy respectively, while a percentage difference of -9% and -50% was found for the 2D model. Tool wear was found to have a significant effect on measured cutting forces. [ABSTRACT FROM AUTHOR]

Better control of fibre composites machining requires reliable surface roughness and damage characterisation measurements. The performance and tool wear rate of three different state of the art CVD and PCD cutting tools manufactured for carbon fibre machining were compared in wet and dry conditions. Machined surfaces were characterised by areal surface roughness parameters using a novel focus variation optical system. The tool wear and cutting forces were recorded up to 50 linear meters of machining or until tool failure. Results showed that wet machining conditions reduced tool failure; and that the CVD tool in wet conditions machined the greatest distance of 26m before reaching an average roughness limit of 3 μm. The tool type was found to be the most significant parameter on the surface quality. The optical system was found to be a useful tool for measuring roughness of individual plies and characterising machining induced surface damage. [ABSTRACT FROM AUTHOR]