2. Rotary ultrasonic machining of CFRP composites

Abstract

Drilling is a major machining process performed for assembly purposes in CFRP composite applications. Traditional methods of drilling CFRP composites (including twist drilling and its relative methods) have many machining problems such as short tool life, poor hole quality and low machining efficiency. There are critical needs to develop time-efficient and cost-effective processes for drilling CFRP composites. Rotary ultrasonic machining (RUM) can be one of them. This chapter presents RUM of CFRP composites, including definitions, features, machine elements (system set-up) as well as experimental and theoretical investigations. These investigations include effects of input variables (tool rotation speed, feed rate and ultrasonic power) on cutting force, torque, cutting temperature, edge quality, surface roughness, burning of machined surface, tool wear, material removal rate (MRR), power consumption and feasible regions during RUM of CFRP composites. Introduction CFRP composites Properties and applications of CFRP compositesFiber reinforced plastic composites can be classified into different categories based on the type of fibers. The fibers include glass fiber, carbon fiber (graphite fiber), polyethylene fiber, boron fiber, ceramic fiber and kevlar fiber [36].Carbon fiber reinforced plastic (CFRP) composites consist of two materials: carbon fibers and polymer. Within CFRP composites, the carbon fibers are surrounded in one or more orientations in a polymer matrix and can be in the form of small particles, whiskers or continuous filaments. The carbon fibers are used to support the load, while the polymer matrix is used to bind and protect the fibers and transfer the load to the reinforcing fibers [10,23,28]. The polymers used as the matrix of CFRP composites are generally classified as thermoset (epoxy, phenolic, polyester, etc.) or thermoplastic (polyether-ether-ketone, polyimide, etc.) resins [53].CFRP composites have a variety of attractive properties, including low density (lower than aluminum, providing light-weight engineering solutions); high stiffnessto-weight ratio (stiffer than titanium); excellent fatigue, corrosion and wear resistance; outstanding toughness and damage tolerance (enabled using proper fiber orientations); high dimensional stability; excellent chemical resistance (controlled by the polymer matrix); and low friction coefficient, thermal expansion, electrical conductivity [10,21,37,41,51,53].

A mechanistic ultrasonic vibration amplitude model during rotary ultrasonic machining of CFRP composites

“…Ultrasonic vibration amplitude, one of the most important input variables in RUM, is controlled by ultrasonic power supply. Numerous studies have found that ultrasonic vibration amplitude has direct influences on almost all output variables in RUM [7,8,13,14,22,23]. Ultrasonic vibration amplitude measurement would be thus beneficial for exploring the explanations for some experimentally observed phenomena and predicting the results of output responses in RUM.…”