Micromilling Responses of Hierarchical Graphene Composites

Abstract

The objective o f this research is to examine the micromachining responses o f a hierarchi cal three-phase composite made up o f microscale glass fibers that are held together by an epoxy matrix, laden with nanoscale graphene platelets (GPL). To this end, micromil ling experiments are performed on both a hierarchical graphene composite as well as on a baseline two-phase glass fiber composite without the graphene additive. The composite microstructure is characterized using transmission electron microscopy (TEM) and scan ning electron microscopy (SEM) methods. Tool wear, chip morphology, cutting force, surface roughness, and fiber-matrix debonding are employed as machinability measures. In general, the tool wear, cutting forces, surface roughness, and extent o f debonding are all seen to be lower fo r the hierarchical graphene composite. These improvements are attributed to the fact that GPL improve the thermal conductivity o f the matrix, provide lubrication at the tool-chip interface, and also improve the interface strength between the glass fibers and the matrix. Thus, the addition o f graphene to a conventional twophase glass fiber epoxy composite is seen to improve not only its mechanical properties but also its machinability.

A Review on Nanocomposites. Part 2: Micromachining

“…Although graphene has high potential in terms of reinforcing various matrix materials such as polymers, metals or ceramics, it has been seen that few studies have investigated these graphene-based nanocomposites recently. One of the early studies about micro-machinability of graphene-based nanocomposite has employed graphene platelets (GPL) as the secondary filler [49]. The main objective of this study is to consider the differences in micromachining responses between two-phasecomposite (epoxy/GF) and three-phase composite (epoxy/GF/GPL).…”

“…In addition, an elevation of cutting force has been observed in this case that was different from the aforementioned studies. While adding graphene [49] or CNTs [45] have in polymer matrix have been indicated the main factor for cutting forces reduction due to two reasons: reduce friction coefficient in tool-chip interaction that lead to superior rake face lubrication and low interfacial failure strength between polymers and nano-fillers, this study, however, differently claimed a high specific surface area of GPL increasing tool-GPL interaction associated with its rough/wrinkled morphology enhancing mechanical interlock within PC matrix were two reasons that leading to cutting forces rise.…”

“…On the other hand, tool wear has been received more attention in case of micromachining polymer/graphene nanocomposites [49,54,56] that indicated its importance as a machinability indicator. By discussing aforementioned studies, it could be seen that effects of graphene addition associated with cutting speed and feed rate have been considered changing the thermos-mechanical properties of the based polymer matrix, hence affecting the cutting mechanism, chip formation and subsequent cutting force, surface roughness and tool wear.…”

“…In addition, the infestation of CNT and polymer smearing on the machined surface also contributed to its high surface quality. The cutting forces when micromachining PC/CNT nanocomposites were also lower in this case due to the reduction of shear strength for failure than plain PC or the low-quality bonding of PC-CNT[49], especially when high feed rates (shearing-dominated regime) were applied(Figure 13Figure 13). The lower friction coefficient of PC/CNT might also play a key role in cutting forces reduction[50] that has not been addressed by the authors.…”

“…Copyright 2013 by ASME)Schematic of micromilling CNT-based nanocomposite (Reprinted with permission from[51] . Copyright 2013 by ASME) of the matrix-fiber bond's strength to the chip formation and surface generation (Reprinted with permission from[49]. Copyright 2015 by ASME)Influence of the matrix-fiber bond's strength to the chip formation and surface generation (Reprinted with permission from[49].Copyright 2015 by ASME) of cutting speed on cutting force and surface roughness when micromachining epoxy/0.8 vol.% GF and epoxy/0.8 vol.% GF/0.2 wt.% GPL composites (Reproduced from [49])Effect of cutting speed on cutting force and surface roughness when micromachining epoxy/0.8 vol.% GF and epoxy/0.8 vol.% GF/0.2 wt.% GPL composites (Reproduced from [49]) of cutting speed and filler content on cutting force when micromilling different polymer nanocomposites at feed rate = 3 µm/tooth (Reproduced from [44, 54])Effect of cutting speed and filler content on cutting force when micro-milling different polymer nanocomposites at feed rate = 3 µm/tooth (Reproduced from [44, 54]) trends of cutting forces as a function of graphene addition when micromachining graphene reinforced PMNCs (Reproduced from [49, 54, 56])Different trends of cutting forces as a function of graphene comparison of the standardized effects of various parameters on cutting forces for Mg/Graphene nanocomposites (Reproduced from [57]Quantitative comparison of the standardized effects of various parameters on cutting forces for Mg/Graphene nanocomposites (Reproduced from [57]) cutting energy when micro-milling Mg and Mg/10 vol.% SiC nanocomposite (Reproduced from [58])Specific cutting energy when micro-milling Mg and Mg/10 vol.% SiC nanocomposite (Reproduced from [58]) of SiC content on cutting force when micro-milling Mg/SiC nanocomposite (Reproduced from [59])Effect of SiC content on cutting force when micro-milling Mg/SiC nanocomposite (Reproduced from [59]) of feed rate on cutting force when micromachining Mg/ceramic nanocomposites (Adapted from [59, 60])Effect of feed rate on cutting force when micromachining Mg/ceramic nanocomposites (Adapted from[59,60]) showing the correlations between micro-machinability of nanocomposites and some basic factors…”