A viscoelastic bonded particle model to predict rheology and mechanical properties of hydrogel spheres

The use of hydrogels has exponentially increased in recent years in many fields, such as biology, medicine, pharmaceuticals, agriculture, and more. These materials are so widely used because their mechanical properties change drastically with the different chemical compositions of the constituent polymer chains, making them highly versatile for different applications. We introduce a numerical simulation tool that relies on the Discrete Element Method to reproduce and predict the behavior of hydrogel spheres. We first use a benchmark test, namely an oscillatory compression test on a single hydrogel, to calibrate the model parameters, obtaining a good agreement on the material’s rheological properties. Specifically, we show that the normal modified storage and loss moduli, E’ and E”, obtained in the simulation match the experimental data with a small relative error, around 3%, for E’ and 11% for E”. This result aligns with recent work on numerical modeling of hydrogels, introducing a novel approach with bonded particles and a viscoelastic constitutive relation that can capture a wide range of applications thanks to the higher number of elements. Moreover, we validate the model on a particle-particle compression test by comparing the simulation output with the contact force in the compression direction, again obtaining promising results.