The team of Professor Fan Yubo and Professor Wang Lizhen from the Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education and Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, conducted a biomechanical study on the lightweight reinforcing and toughening mechanism of walnut shell. The research result, titled “Fracture resistance biomechanisms of walnut shell with high-strength and toughening”, was published in the famous comprehensive journal Advanced Science. Professor Fan Yubo is the corresponding author of this paper, while Professor Wang Lizhen and postdoctoral fellow Xu Peng are the co-first authors (Adv.Sci.2023, 2303238).
The research team has been conducting basic and technical research to address the challenges of high overload damage and protection, such as high damage rate and difficult protection, which are essentially problems caused by unclear damage mechanism/ tolerance limit or insufficient efficiency of protection technology and equipment. The research is another important progress in the field of biomechanics of injury and protection, funded by the Joint Fund of the National Natural Science Foundation of China (U20A20390) and other projects.
In this study, it is found for the first time that the asymmetric distribution of the center of mass and centroid causes rotational energy consumption after collision and decreases the rebound height and impact peak value. It is also revealed that the unique distractive wood structure in a walnut can enhance the overall rigidity, resist the large deformation caused by external force, avoid cracking and thus realize the protection of the kernel. The mechanical properties and porosity of the walnut shell show a unique S-shape gradient distribution, which enhances the cushioning capacity of the shell and reduces the peak load based on the mechanical theory, numerical simulation and experimental verification. In addition, the single cellwall of the shell is concave and polycellular with tensile expansion characteristics, and the porous structure on the cellwall can divert cracks, increase the energy consumption in the process of deformation and fracture of the cellwall, and realize the strengthening and toughening on the micro scale.
Mechanical properties and gradient porosity distribution of walnut shell
Microstructure of single cellwall of walnut shell and its strengthening and toughening mechanism
Link to the Article:
https://onlinelibrary.wiley.com/doi/10.1002/advs.202303238
Reported by Ni Yikun
Reviewed by Li Deyu
Edited by Wang Qing
Translated by Yao Zipeng
