Abstract
A great deal of attention is currently paid to recycling or reusing carbon fibres, as it improves sustainability and the lifetime of carbon products. The applicability of recycled carbon fibre–reinforced polymer (rCFRP) composite materials is supported by the results of material scientists; however, the machinability of rCFRPs has not been analysed yet. The machinability of virgin and rCFRPs was compared by analysing cutting force and torque in drilling. Six different CFRPs (virgin and recycled CFRPs with different reinforcing structures) were drilled at three feed levels using two different solid carbide cutting tools. The cutting force and torque were measured with a KISTLER 9257BA dynamometer, processed, and analysed by fast Fourier transformation (FFT) and analysis of variance (ANOVA). The experimental results proved at a significance level of 0.05 that the recycled/virgin status of the applied CFRPs significantly influences both the thrust force and drilling torque of each CFRP. Furthermore, the cutting force and torque are higher in rCFRPs than in virgin CFRPs at each reinforcing structure. The present study suggests spreading rCFRP applications, as there are no essential barriers against them from the point of view of drilling force and torque.
Highlights
Carbon fibre–reinforced polymer (CFRP) composites have superior material properties, like excellent specific strength, good chemical and dimensional stability, high damping ability, outstanding corrosion resistance, and good damage tolerance [1]
While the cutting resistance of the material remains quasi-consistent during drilling, an increase in tool wear can result in increased thrust force and torque and vice versa [10]
As the thrust force diagrams, the torque diagrams are divided into different sections highlighted by different colours, which correspond to the drilling workflow steps illustrated in Fig. 10b, d
Summary
Carbon fibre–reinforced polymer (CFRP) composites have superior material properties, like excellent specific strength, good chemical and dimensional stability, high damping ability, outstanding corrosion resistance, and good damage tolerance [1]. The use of CFRP is spreading fast in Pimenta and Pinho [7] analysed the microchemical properties and reinforcement architectures of recycled carbon fibres. They achieved 80% of fibre strength and similar quality recycled fibres compared to virgin CFRPs. They achieved 80% of fibre strength and similar quality recycled fibres compared to virgin CFRPs They highlighted that rCFRPs would spread in applications requiring high toughness or damage tolerance. The International Journal of Advanced Manufacturing Technology Based on their promising results concerning tensile, flexural, and impact strength, they expect a wide range of potential applications of rCFRPs in the near future. The applications of recycled carbon fibre–reinforced polymer (rCFRP) composites are limited and no studies have been published on their machinability, their main cutting characteristics and challenges may be similar to those of virgin CFRPs: (i) difficult to cut mainly due to the inhomogeneous and anisotropic characteristics, and the abrasive wear effect of carbon fibres on the cutting tool [10, 11]; (ii) chip removal mechanisms are mainly influenced by the fibre cutting angle (θ), followed by the cutting edge radius (rβ) and rake angle (γ) [12, 13]; (iii) high axial cutting forces and inappropriate support of laminated CFRP layers result in significant machining-induced damage formations i.e. delamination, burrs, tearing, and fibre pull-outs [14,15,16,17,18,19]; (iv) difficult to clamp due to their relatively low stiffness and hardness [20]; and (v) often machined in dry condition because of the wettability of composites; the removal of carbon chips from the cutting space often requires a vacuum equipment due to their adverse impact on machine tool elements and on human health [21]
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