Journal of Bionic Engineering (2023) 20:2732–2741 https://doi.org/10.1007/s42235-023-00393-3

Effects of Geometrical Characteristics of Suture on Fracture Resistance of Walnut Shell

Peng Xu1 · Lizhen Wang1 · Jinglong Liu1 · Yanxian Yue1 · Yubo Fan1,2

Lizhen Wang lizhenwang@buaa.edu.cn * Yubo Fan yubofan@buaa.edu.cn

1 Key Laboratory of Biomechanics and Mechanobiology (Beihang University), Ministry of Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing 100083, China

2 School of Engineering Medicine, Beihang University, Beijing 100083, China

Abstract：Nut shells have good impact and fracture resistance, but many kinds of nut shells have suture structures with low bonding strength. Therefore, the mechanism of impact and fracture resistance of nut shells as a whole is important to study, particularly given that sutures maintain low bonding strength. In this study, we investigated the effect of the geometrical characteristics of sutures (morphology, thickness, and number) on the overall fracture resistance of walnuts, based on mechanical tests of C-ring samples, microstructure analysis after cracking, quantitative analysis of suture geometric model, and numerical simulations. We found that the cracking of walnuts was mainly caused by tensile stress, and the bonding strength was approximately 2.48?±?0.64 MPa. We discovered that the thickness of the suture was 1.55?±?0.32 times thicker than the shell, which improved the fracture resistance ability by more than 28.4%. The undulating and inclined morphology of the walnut suture also increased the fracture force. Additionally, an appropriate suture number reduced the cracking of walnuts. In conclusion, our study sheds light on the physiological function of walnut sutures from a biomechanical perspective and provides useful references for designing fracture resistance measures in thin shell structures.

Keywords： Fracture resistance · Walnut · Suture · Bonding strength · Numerical simulations · Biomechanics