چكيده لاتين
Hydrogels possess unique properties due to the presence of water in their network structure, making them suitable for various biological and engineering applications such as tissue engineering and prosthetics. However, the main weakness of these materials in the mentioned applications can be attributed to their ability to withstand tensile and cyclic loads. Thus, enhancing the strength and investigating the fatigue of hydrogels presents a significant challenge for researchers in this field. In this study, the experimental and numerical analysis of the fatigue of cellulose-based hydrogels is examined to increase ultimate strength, toughness, and fatigue life. To create the desired hydrogel sample, which includes cellulose, acrylic acid, acrylamide, sodium hydroxide, and ammonium persulfate, a mixture was prepared with 0.3 grams of cellulose, 3.75 cc of acrylic acid, 6.6 cc of a 20% weight/volume sodium hydroxide solution, 2.5 cc of a weight/volume acrylamide solution, and 1 cc of a 3.7% weight/volume ammonium persulfate solution. To enhance mechanical properties and maintain elastic characteristics, variations in the amount and concentration of the crosslinking agent and the amount of water in the hydrogel are utilized. Finally, by changing the amount of the crosslinking agent to 0.008 grams and 3 cc of water, so that the final strength reached 3.2 times more than the initial state. With the completion of the hydrogel manufacturing, the uniaxial tension and cyclic fatigue tests were performed with four final tensions of 3.88, 4.2, 4.52, and 4.92, which are less than the maximum elongation of the cellulose base hydrogel. Considering these ultimate tensile values, the analytical relationship governing the failure cycle of the cellulose-based hydrogel is presented, and the S-N diagram obtained from the experimental and analytical results is mentioned .Next, we went to the numerical analysis and by considering the hyperelastic behavior of the second order Ogden model and Mullins damage for the hydrogel in question, the values of the ultimate stress of the first cycle, the failure cycle and the failure stress of the final cycle were modeled in Abaqus software. By examining the results obtained from the experimental fatigue tests and the numerical model, a suitable convergence between the two analyzes was observed and the correctness of the numerical results was confirmed.
The improved cellulose-based hydrogel maintains its elasticity and at the same time shows an acceptable strength and toughness, so that its final strength value is 0.699 MPa and the maximum elongation of the sample is 5.22.
