Constitutive model for shape memory polymer and its thermodynamic responses in finite element analysis

Article type: Research Article

Authors: Wu, Jianlei^{a; b; c; *} | Guo, Jing^{b; d; e; *} | Luo, Yong^c | Sun, Jianfeng^{b; d; e} | Xu, Liangwei^a | Zhang, Jianxing^f | Liu, Yunfeng^g

Affiliations: [a] Intelligent Equipment Research Institute, Ningbo Polytechnic, Ningbo, Zhejiang, China | [b] Department of Orthodontics, Ningbo Stomatology Hospital, Ningbo, Zhejiang, China | [c] School of Materials Science and Physics, China University of Mining and Technology, Xuzhou, Jiangsu, China | [d] Savaid Stomatology School, Hangzhou Medical College, Hangzhou, Zhejiang, China | [e] Savaid Medical Institute for Stomatology and ENT, Ningbo, Zhejiang, China | [f] Department of Stomatology, Zhejiang Hospital, Hangzhou, Zhejiang, China | [g] College of Mechanical Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang, China

Correspondence: [*] Corresponding authors: Jianlei Wu, Intelligent Equipment Research Institute, Ningbo polytechnic, Ningbo, Zhejiang 315800, China. E-mail: wujl90@163.com. ORCID: 0000-0002-5470-5626. Jing Guo, Department of Orthodontics, Ningbo Stomatology Hospital, Ningbo, Zhejiang 315016, China. E-mail: guojing@sdu.edu.cn.

Abstract: BACKGROUND: As a new intelligent polymer material, shape memory polymer (SMP) was a potential orthodontic appliance material. OBJECTIVE: This study aimed to investigate the thermodynamic responses of SMP under different loads via finite element analysis (FEA). METHODS: FEA specimens with a specification of 0.1 × 0.1 × 1 mm were designed. One end of the specimen was fixed, and the other was subjected to displacement load. Different loading, cooling, and heating rates were separately exerted on the specimen in its shape recovery process and used to observe the responses of the SMP constitutive model. Furthermore, specimens with various tensile elongation and sectional areas were simulated and used to elucidate their effect on shape recovering force. RESULTS: The specimens obtained a similar stress of 0.5, 0.44, and 1.07 Mpa for different loading, cooling, and heating rates after a long time. The shape recovering force of specimen increased from 0.0102 to 0.0315 N when the elongation improved from 10% to 40% and to 0.0408 N when the sectional areas were expanded to 0.2 × 0.2 mm. CONCLUSION: The stiffness of SMP was small at a high temperature but large at a low temperature. The effects of the loading, cooling, and heating rates on SMP can be eliminated after a long time. Furthermore, it was possible to increase the recovering force by increasing the elongation or expanding the sectional area of the specimen. The force was quadratically dependent on the elongation ratio.

Keywords: Shape memory polymer, constitutive model, thermodynamic response, finite element analysis

DOI: 10.3233/THC-240078

Journal: Technology and Health Care, vol. 32, no. 5, pp. 3383-3391, 2024