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The review traces the development of composite shafts in varied applications. The different theoretical and experimental aspects of dynamics of composite shafts, under investigation for the past two decades, are reviewed and the state of the art discussed including possible future developments.Keywords." Composite shaft, dynamics, driveshaft design, non-metallic rotors INTRODUCTION Present day rotors have predominantly metallic shafts. Use of fiber reinforced composites has been attempted in a few specific applications. Studies on composite shafts started in 1970's. The most important development of composite shafts has taken place in aerospace (helicopter) industry [Kraus andDarlow, 1987 andBielefield, 1994], and automotive applications [Kliger and Yates, 1980, Golding, 1982and Hoffmann et al., 1994. Other applications include the use of composite shafts as quill shaft by Spencer [1989], an aircraft power take off shaft by Garguilo [1986], generator shaft by Raghava and Hammond [1984], shaft for a cooling tower by Berg [1989], a papermill by Cox [1994] and naval propulsion systems by Wilhelmi et al. [1986]. The two U.S. patents by Worgan and Smith [1978] and Yates and Rezin [1979] indicate that the preliminary hurdles to a composite driveshaft design were overcome. Fromknecht [1992] highlighted the possible benefits accruing from the use of composite shafting in mechanical power transmission.In the early developments, composite shafts were designed to operate in the sub-critical range. Therefore, initial studies were directed towards design requirements and in overcoming the problems in practical application. Subsequently, in order to derive greater advantage in terms of reduction of weight, the possibility of super-critical operations of composite shafts was explored. Thus, the present trend in research, as highlighted by Gupta and Singh [1996], emphasizes such aspects as rotordynamic analysis, elaborate optimization procedures, cost sensitivity analyses, and possibility of supercritical operation. Yates [1980] discussed the design and material considerations for composite driveshafts in automotive applications, initially, the materials used for the driveshafts were glass/epoxy and boron/epoxy. However, as developments in composite technology continued, carbon fibers became more readily available. In many of the current applications they replaced boron fibers, which had proved too costly and were difficult to process. In automotive driveshafts, carbon fibers were found to be particularly suitable. Hybridization with glass/epoxy was also tried, and proved cost effective as shown by Linsenmann [1978].Belingardi et al. [1990] showed that carbon fiber becomes a necessity when a critical balance between torque, diameter, length and natural frequency cannot be achieved with metallic or glass/epoxy configurations. The stepwise description of the complete design procedure which is adopted for replacement of a two piece metallic automotive driveshaft by a single piece composite shaft was described by Spencer and ...

The integration of variable distributed generations (DGs) and loads in microgrids (MGs) has made the reliance on communication systems inevitable for information exchange in both control and protection architectures to enhance the overall system reliability, resiliency and sustainability. This communication backbone in turn also exposes MGs to potential malicious cyber attacks. To study these vulnerabilities and impacts of various cyber attacks, testbeds play a crucial role in managing their complexity. This research work presents a detailed study of the development of a real-time co-simulation testbed for inverter-based MGs. It consists of a OP5700 real-time simulator, which is used to emulate both the physical and cyber layer of an AC MG in real time through HYPERSIM software; and SEL-3530 Real-Time Automation Controller (RTAC) hardware configured with ACSELERATOR RTAC SEL-5033 software. A human–machine interface (HMI) is used for local/remote monitoring and control. The creation and management of HMI is carried out in ACSELERATOR Diagram Builder SEL-5035 software. Furthermore, communication protocols such as Modbus, sampled measured values (SMVs), generic object-oriented substation event (GOOSE) and distributed network protocol 3 (DNP3) on an Ethernet-based interface were established, which map the interaction among the corresponding nodes of cyber-physical layers and also synchronizes data transmission between the systems. The testbed not only provides a real-time co-simulation environment for the validation of the control and protection algorithms but also extends to the verification of various detection and mitigation algorithms. Moreover, an attack scenario is also presented to demonstrate the ability of the testbed. Finally, challenges and future research directions are recognized and discussed.