Formability mechanism of CFRP sheets using multiscale model based on microscopic characteristics of thermosetting resin
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ORIGINAL PAPER
Formability mechanism of CFRP sheets using multiscale model based on microscopic characteristics of thermosetting resin Tetsuo Oya1
· Akihiro Nishino2
Received: 20 June 2020 / Accepted: 22 September 2020 © Springer Nature Switzerland AG 2020
Abstract This study was undertaken to attempt to establish the press-forming of carbon fiber-reinforced plastic (CFRP) sheets through a forming simulation. Since press-forming induces large plastic deformation of a material, a reliable simulation requires accurate modeling of the plastic deformation of resin. However, there has been little research on the deformation mechanism of thermosetting resins under large plastic forming, which is targeted in this study, and therefore no appropriate plastic deformation model of a resin has been established. Thus, a new model was constructed for a thermosetting resin on the basis of plastic deformation characteristics considering the microscopic mechanism. In the proposed model, the breakage of molecular chains of a thermosetting resin is considered. A molecular dynamics simulation of epoxy resin determined the effect of this molecular chain breakage. It was confirmed that the proposed model can appropriately represent the mechanical characteristics of an actual thermosetting resin. Furthermore, using this model, the numerical analysis of a CFRP sheet through its representative volume element was carried out, and the result explained the improved formability of CFRP at high temperatures, as observed in related experiments. Keywords Sheet forming · Formability · CFRP · Thermosetting resin · Finite element analysis · Molecular dynamics
1 Introduction Carbon fiber-reinforced plastic (CFRP) composed of carbon fibers and a thermosetting resin, has both lightness and strength, and its application as a new structural material has been drawing attention. In recent years, its application to not only limited fields such as airplanes and sports equipment, but also general industries such as the automobile industry has been increasing, and the demand for CFRP is increasing year by year. However, low production efficiency has been a problem in the manufacture of CFRP products. This is because no plastic working method such as press-forming has been established owing to the poor ductility of CFRP. To conduct press-forming on CFRP sheets, it is necessary to understand the plastic deformation behavior and fracture criteria of CFRP.
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Tetsuo Oya [email protected]
1
Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Japan
2
NIPPON STEEL Chemical & Material Co., Ltd., Tokyo, Japan
In recent studies, it has been confirmed that CFRP shows sufficient ductility to realize press-forming at 100 ◦ C, and it has been found that the formability of CFRP has temperature dependence. Uriya et al. (2015) and Uriya and Yanagimoto (2016) performed press-forming on CFRP sheets at different temperatures. Uriya and Yanagimoto (2017a) also performed an Erichsen test on CFRP sheets, which showed that CFRP
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