Mechanical Properties Analysis of Scaffold Material Using Nonlinear Least Squares Fitting by Hyperelastic Model

Abstract—Nowadays, the number of chronic wounds is on the rise. Wounds can caused by many problems such as disease, burn, ulceration, trauma and accident. Tissue engineering aims to produce porous scaffold biomaterials to regenerate damaged tissues to growth of new tissue. This research, gelatin was blended with Carboxymethylcellulose (CMC) in various conditions and fabricated to porous structure by using freezedrying method. All scaffolds were strengthen their structure by dehydrothermal crosslinking. Normally, the scaffold behavior is likely to be a foam-like hyperelastic material. Therefore, this research was selected Blatz-Ko model to describe the material behavior that acts as a foam rubber. This model could apply with both cases of compressible and incompressible material. The mechanical characterization of the scaffold was investigated by compressive test using universal testing machine (UTM). The experimental data obtained from the UTM was used to plot the stress-strain curve. The initial shear modulus of the material was identified by function derived from Blatz-Ko hyperelastic model using non-linear curve fitting method. The result revealed that Blatz-Ko model could fit curve at approximately 7% strain which was suitable for infinitesimal strain theory. The dehydrothermal treated scaffold with 90:10 gelatin/CMC ratio showed the highest shear modulus of 10.47±1.21 kPa. The structural collapse occurred in 60:40 gelatin/CMC scaffold. The physical characterization was done by using scanning electron microscopy (SEM) to investigate surface morphology and pore size of scaffolds. The results showed the appropriate pore size of the scaffold with average pore size of 117 μm to 197 μm. The 90:10 gelatin/CMC scaffold showed the biggest pore size.

Index Terms—Hyperelastic model, Blatz-Ko, mechanical properties, scaffold, gelatin, carboxymethylcellulose.

Fasai Wiwatwongwana is with Department of Advanced Manufacturing Technology, Faculty of Engineering, Pathumwan Institute of Technology, 833 Rama 1 Road, Wangmai, Pathumwan, Bangkok 10330, Thailand (email: fasaiw227@gmail.com).
Nattawit Promma is with Department of Mechanical Engineering, Faculty of Engineering, Chiang Mai University, 239 Huay Kaew Road, Muang District, Chiang Mai 50200, Thailand (e-mail: nano_504@hotmail.com).

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Cite: Fasai Wiwatwongwana and Nattawit Promma, "Mechanical Properties Analysis of Scaffold Material Using Nonlinear Least Squares Fitting by Hyperelastic Model," International Journal of Materials, Mechanics and Manufacturing vol. 8, no. 3, pp. 84-88, 2020.

Copyright © 2020 by the authors. This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).