Abstract
This article presents a simple framework for predicting the occurrence of delamination during milling of unidirectional carbon-fiber-reinforced plastics (CFRPs), based on a concept of effective critical cutting zone. To validate the concept, sets of milling experiments were conducted on unidirectional CFRP samples of varying fiber orientations and the delamination signature was measured through microscopic images. By observing the damage extent for different fiber orientation angles and different fiber cutting angles for up-milled and down-milled edges, and correlating them with different material removal mechanisms, it has been shown that the damage mainly depends on the portion of the fiber cutting angles that lie within the effective critical milling zone. Both the delamination and the normal cutting forces were found to be strongly dependent on the range of angles in this zone. In addition, it is shown that the cutting force may be used as a good approximation to determine the effect of machining/process parameters on the ensuing delamination damage during milling of CFRPs. For the tested samples, the normal cutting force decreased with an increase in the cutting speed and it increased with an increase in the feed rate of the cutting tool.
Highlights
The use of carbon-fiber-reinforced plastics (CFRPs) has grown considerably in recent years due to their superior properties such as light weight and high strength/stiffness
By making 5 mm slots on unidirectional carbon-fiberreinforced plastics (CFRPs), it was found that the damage occurring on the slot edges clearly vary between specimens of different fiber orientations
Maximum damage is experienced when eccr = 90°, that is based on Table 3 when machining is conducted on a specimen that is aligned at a fiber orientation of ø = 90° and minimum damage is seen when eccr = 45°, that is machining is done on a specimen aligned at a fiber orientation of ø = 0°
Summary
The use of carbon-fiber-reinforced plastics (CFRPs) has grown considerably in recent years due to their superior properties such as light weight and high strength/stiffness. It is critical to understand and predict the mechanisms of material removal in composites for achieving desired quality of the machined surfaces.[4,5]. Wang et al.[6] performed an experimental study on edge trimming of unidirectional composites with polycrystalline diamond tools. They found that the fiber orientation plays a significant role in the material removal process of fiber composites. The effect of cutting parameters and tool geometry on the sub surface damage in machined samples was investigated by Nayak and Bhatnagar.[14] In most of the earlier experimental studies above, flank wear phenomenon was clearly observed during milling composites.
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