Browsing > By author > Lancioni Giovanni

Understanding crack propagation mechanisms in thin elastomeric membranes is crucial for various engineering applications, yet accurately modeling their complex behavior poses significant challenges due to the inherent material nonlinearity. In this contribution, we present a novel viscoelastic constitutive model specifically tailored to capture the time-dependent response of elastomers subjected to mechanical loading and damage, with particular emphasis on finite strain effects. Developed by following the classical approach to phase field fracture, the model incorporates both short and long-term nonlinear elastic energy densities \cite{Ciambella2024}, as well as dissipation mechanisms \cite{Fischer2014}, that are attenuated by damage through distinct degradation functions.

Our primary objective is to accurately predict crack propagation velocities in thin viscoelastic membranes, accounting for the geometric and material nonlinearities that characterize their behavior, a problem tested in several recent papers in the literature. Energy dissipation around a propagating crack is the primary mechanism for the enhanced fracture toughness in elastomers. Such mechanism is spatially non-uniform and is highly coupled to the crack propagation process due to both the history-dependent nature of viscoelasticity and the large deformations involved. It is mainly driven by two processes: one intimately associated with viscoelasticity, which is controlled by the breaking and healing kinetics of ionic bonds as well as the degree of chemical crosslinking in the bulk material, and another occurring in the fracture process zone where the polymer chains experience extreme stretches, leading to significant strain-stiffening before their ultimate rupture.

By coupling finite strain elasticity, viscoelasticity, and damage, our model allows us to better highlight the combined role of material nonlinearity and dissipative mechanisms in crack propagation speeds. To validate the model, we conduct numerical simulations of a range of mechanical tests, including 1D and 2D simulations, that showcase the model's ability to capture the interplay between geometric nonlinearity, viscoelasticity, and crack propagation.