PSI - Issue 52

Dita Puspitasari et al. / Procedia Structural Integrity 52 (2024) 410–417 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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or in this case air, since the samples were freeze-dried, will drain and escape from the hydrogel. Therefore, even a small load applied is possible to deform the hydrogel. 3.4. Compression Simulation

Fig. 4 a) 2D porous model from Matlab b) Meshed 2D porous model.

Table 4. Compression and tensile test data for hyperelastic validation test

Compression test data Tensile test data Pressure (Pa) Volume Ratio Stress (Pa) Strain 1.20E+05 0.3 1.51E+07 0.05 4.70E+05 0.5 1.86E+07 0.1 1.80E+06 0.8 2.14E+07 0.15 2.34E+07 1 2.32E+07 0.2 9.10E+07 1.05 2.47E+07 0.25 1.31E+08 1.07 2.81E+07 0.429 1.36E+08 1.08 2.72E+07 0.449

Fig 4a shows result of Matlab code to model 2D porous sample with size 10 mm x 8 mm. Resulting 2D model from Matlab then processed to be simulated in Abaqus CAE. It used 2D deformable sheet. Fig 4.b shows meshed model of 2D porous. For the material model, test data from compression test results and tensile test data from previous studies for the same material are used (He et al. (2017)). Compression and tensile test data (Table 4) were input into Abaqus for analysis. It is validated with Ogden strain energy function (N=1). Ogden model is selected because it can accurately describe the behavior of rubber-like materials. It is based on the idea that the strain energy of a material can be expressed as a power series expansion in terms of the principal stretches. The model also can be characterized by a set of material parameters that can be determined from experimental data.

Table 5. Ogden Strain and Neo-Hookean Energy Function

Ogden Strain Energy Function with N=1

μ

α

D

53713693.8

-3.118

7.423

Table 5 shows hyperelastic engineering constant from validate data of hydrogel compression and tensile test. In the Ogden strain energy function, μ, α, and D are material parameters that characterize the behavior of the material. Specifically: μ (mu) is a scaling parameter that determines the overall stiffness of the material. It is related to the shear modulus o f the material, α (alpha) is a dimensionless parameter that determines the shape of the stress -strain curve. It controls the degree of nonlinearity in the materi al’s response, D is a material parameter that determines the degree of compressibility of the material. It is related to the bulk modulus of the material. Ogden strain energy (N=1)