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Machining process of glass fiber composites usually induces delamination damage. The presence of delamination may cause changes in the mechanical characteristics of the composite structures. In this research, a comprehensive experimental study is performed to analyze the influence of different parameters such as thermal fatigue, lay-up arrangement, resin type, feed rate and cutting velocity on the delamination of glass fiber composites under different drilling processes. Besides, influence of ultrasonic vibration exerting on the tool as a new and high-tech process is investigated. To follow this aim, different composite specimens with various resin types and lay-up arrangements are fabricated and a thermal fatigue condition is provided. Additionally, the Taguchi method is employed to obtain the optimized damage reduction condition in terms of mentioned parameters. The results indicated that thermal fatigue and unsymmetrical lay-up arrangement result in more delamination damage. It was also established that the influence of mentioned parameters is more considerable in higher cutting velocities. Moreover, ultrasonic vibration application is suggested to have the least delamination damage. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced plastics are used in variety of industrial and constructional applications for their superb mechanical and physical properties. Delamination is one of the most important and prevalent damages in machining of glass fiber reinforced plastics. Diamond core drills have the capability of simultaneously drilling and grinding of fiber reinforced plastics, which results in hole quality improvement. Rotary ultrasonic-assisted drilling is the new machining process to drill holes on fiber reinforced plastics and has attracted increasing attention in recent years. In this paper, thrust force and delamination in rotary ultrasonic-assisted drilling of glass fiber reinforced plastics using diamond core drill have been investigated. A proper ultrasonic system for a core drill in ABAQUS was designed and fabricated. Influence of ultrasonic vibration and then tool grain size, fiber-volume fraction and machining parameters including spindle speed and feed rate on thrust force and delamination was investigated. Higher thrust force induces more delamination. As a result of the study, less delamination was achieved in ultrasonic-assisted mode by using a tool with larger grain size onto lower fiber-volume fraction composites. Additionally, experiments showed that lower spindle speed and higher feed rate induce more delamination. [ABSTRACT FROM AUTHOR]

Application of glass fiber reinforced polymers (GFRP) has been appreciably increased in recent decades because of their admirable properties. Thus, various investigations are focused in machinability of GFRPs. Delamination is one of the major damages in drilling of GFRPs. Rotary ultrasonic drilling (RUD) is a state-of-the-art drilling operation that has been noticeably considered in composites machining industry. In this paper, delamination of GFRPs in RUD process is examined. To reach the goal, appropriate ultrasonic system was established and using a HSS tool, the experiments were carried out. Then, the influence of multi-walled carbon nanotube (MWCNT) addition, thermal fatigue and drilling parameters on delamination were investigated. Additionally, statistical analysis was performed. The results showed that the delamination quality can be well optimized by increase of the cutting velocity. It was also established that thermal fatigue condition results in delamination deterioration. In contrary, addition of nanoparticles enhances the delamination state. [ABSTRACT FROM AUTHOR]