Theoretical Estimation of Thermal Effects in Drilling of Woven Carbon Fiber Composite

Abstract

Carbon Fiber Reinforced Polymer (CFRPs) composites are extensively used in structural applications due to their attractive properties. Although the components are usually made near net shape, machining processes are needed to achieve dimensional tolerance and assembly requirements. Drilling is a common operation required for further mechanical joining of the components. CFRPs are vulnerable to processing induced damage; mainly delamination, fiber pull-out, and thermal degradation, drilling induced defects being one of the main causes of component rejection during manufacturing processes. Despite the importance of analyzing thermal phenomena involved in the machining of composites, only few authors have focused their attention on this problem, most of them using an experimental approach. The temperature at the workpiece could affect surface quality of the component and its measurement during processing is difficult. The estimation of the amount of heat generated during drilling is important; however, numerical modeling of drilling processes involves a high computational cost. This paper presents a combined approach to thermal analysis of composite drilling, using both an analytical estimation of heat generated during drilling and numerical modeling for heat propagation. Promising results for indirect detection of risk of thermal damage, through the measurement of thrust force and cutting torque, are obtained.

4. Numerical modeling of LFRP machining

“…Despite the potential risk of thermal effects in machining CFRP, they have only been analyzed in few works in the literature, mostly based on experimental work. The lack of information related to the numerical prediction of thermal issues in drilling processes has motivated the development of a work focused on the estimation of heat amount from variables easy to measure in process: torque and thrust force [60]. A simple analysis based on energy balance was presented to obtain the heat generated at the interface indirectly from experimental tests.…”

“…The control of the machine tool maintains these parameters, and the resultant torque and thrust force measured at the spindle are a consequence of cutting parameters, material properties and characteristics of the cutting tool, including contact behavior at the interface. Scheme of the drilling process: differential volume removed during the differential time dt and effective cutting edge at the different stages of drilling from entrance to drill exit [60].…”

“…Also with a system for chip aspiration[60].The drilling experiments were conducted without coolant with a feed of 0.1 mm/rev and cutting speed 50 m/min. The characteristics of the workpiece and drill stated for the experiments allowed the calculation of time intervals defined in equations (4.4)-(4.6).…”

Drill-exit temperature characteristics in drilling of UD and MD CFRP composites based on infrared thermography

“…15, have been studied to further elucidate the damage mechanisms within the large angle region of UD and MD [24][25][26][27][28][29][30][31][32][33][34][35][36][37] CFRPs. Fig.…”

“…On the other hand, Zhu et al [27] and Sadek et al [28] demonstrated preliminary simulation results for the drilling-exit temperature characteristics in the drilling of UD and MD CFRPs. The percentage of cutting energy (defined as the heat partition ratio flowing into the workpiece) is critical for the accuracy of the simulation results [29]. However, it is affected instantaneously by the time-dependent fiber cutting angle [30] and the distinct mode of material removal induced by the serious deflection at drill exit [26].…”