Efficient Machining Strategies for Polymer Matrix Composites

Introduction

This chapter delves into the realm of efficient machining strategies tailored for polymer matrix composites. It covers aspects such as tool selection, the risk of damage, and the key parameters involved in this process.

Machining polymer matrix composites (PMCs) poses a significant challenge in terms of cutting tool prerequisites. In contrast to metal cutting, where chip formation is primarily due to plastic deformation, cutting PMCs involves compression shearing and the fracture of fiber reinforcement and matrix (Kaw 2006). This necessitates stringent criteria for cutting edge geometry and material selection. Achieving a sharp cutting edge and a substantial positive rake angle becomes crucial for effectively shearing fibers, while the tool material must possess high hardness and toughness to withstand the fibers' abrasiveness and the intermittent loads induced by their fracture (Daniel, Ishai 2006). The options for tool materials that fulfill these demanding requirements are quite limited.

Urresti (2022) identified that the tool wear and, consequently, the surface integrity in the machining of CFRP composites are predominantly influenced by the fiber orientation, highlighting it as a crucial parameter in the process.

In their research, Bi et al. (2022) carried out both theoretical analysis and practical experiments on CFRP machining, utilizing multi-tooth milling cutters featuring a segmented right-hand helical cutting edge (SRHCE) and a segmented left-hand helical cutting edge (SLHCE). Their findings indicated that the SLHCE tool exhibited greater wear resistance compared to the SRHCE tool. Additionally, they observed that a reduced feed per tooth resulted in increased tool wear and diminished surface quality.

According to Haddad et al. (2014), the use of a multi-tooth cutter in CFRP milling results in reduced damage and lower cutting forces, consistent with the findings reported by Chatelain and Zaghbani (2012). Additionally, Slamani et al. (2015) observed that, during CFRP trimming, the normal cutting force surpassed the feed force.

Lin and Shen (1999) investigated the high-speed drilling characteristics of unidirectional (UD) fiberglass-reinforced composites, exploring a cutting speed range from 210 to 850 m/min. Two types of drills, a twist drill and a multi-face drill, were subjected to testing. Their observations revealed that the axial distance between the outer corner of the cutting edge and the drill tip increased with tool wear. Consequently, the authors proposed a variation in tip height (axial distance) as a parameter for quantifying wear in multi-facial (C-shaped) drills. This discovery was further affirmed by Lin and Chen (1996) in the context of composites drilled with carbon fiber reinforcement. They noted significant wear in tungsten carbide drills as the cutting speed escalated.

Recently, Abd-Elwahed (2022) employed a modeling and optimization strategy grounded in response surface analysis and artificial neural networks. This approach aimed to predict drilling process parameters and optimize cutting conditions for woven glass fiber-reinforced epoxy composites with varying laminate thicknesses. Their findings indicated that achieving optimal results, such as maximizing drilling torque and minimizing the delamination factor, involves employing a low feed rate and high spindle speed during the drilling process.

Mohan et al. (2005) determined that the thickness and drill size collectively constitute the most crucial factors impacting torque, while cutting speed and drill size are the primary influencers of cutting thrust. Erturk et al. (2021) delved into the impact of machining parameters on the drilling performance of GFRP composite, highlighting the influence of tool coating on tribo-mechanical behavior. Their study also emphasized the significant role of drill bit type in determining material temperature.