Elyas Haddadi, Abuzar Eshaghi Oskui,
Volume 24, Issue 5 (4-2024)
Abstract
Linear viscoelastic constitutive laws, such as hyperelasticity with the Prony series, are commonly used in commercial software to simulate polymer materials. However, these models are not accurate regarding large strain problems despite performing well for small strain problems. To gather experimental data for soft adhesives, various shear modes were employed, including monotonic, creep, and low-cycle tests using single-lap shear specimens. These tests were conducted on optically clear adhesives (OCAs). Initially, the validity range for linear viscoelasticity was established, revealing the inability to predict large strains accurately using this approach. Subsequently, the three-network viscoplastic (TNV) model parameters were calibrated experimentally under large strains. The calibration procedures took advantage of variations in loading modes, enhancing the precision and improving the accuracy of the constitutive models. For calibration purposes, it is recommended to utilize the low-cycle loading-unloading test as it offers a suitable and cost-effective means of precision. This approach provides a cost-effective way to accurately predict material behavior, owing to the variations in loading modes. Finally, the characteristic model was used to evaluate the results through the finite element method. The results showed that the proposed model accurately predicts stress values, energy dissipation, and energy loss due to softening
