<p>Bubble growth and collapse in soft materials under tensile pressure have significant implications for material damage. The growth is characterized by the soft material’s fiber network failure and the collapse can impose high strain rate deformation and secondary shock waves to surrounding materials. It is important to understand the mechanism of bubble growth and collapse within the soft material’s fiber network to quantify the critical condition of this event. Early experimental observations showed that the required tensile pressure for cavitation in soft materials is higher than pure water. It is suggested that the inherent elasticity of soft materials causes the delay of cavitation. Since the elasticity arises from the random fiber network of the soft materials, we have postulated that the growing bubble-network interaction plays a significant role.&nbsp;The molecular level heterogeneous cavitation mechanism and bubble growth kinetics in soft gelatin hydrogel and water have been studied. Gelatin, which is derived from collagen, is frequently used as a brain simulant material. As such, the morphology of gelatin is very different from water. In the heterogeneous cavitation study, using molecular dynamics simulation, the pressure requirement for nanoscale cavitation to grow in water and gel has been investigated. The results show that a gel-like structure requires higher pressure for the cavitation to grow, and both gel and water models exhibit strain rate effects on the cavitation threshold pressure. The apparent discrepancies of the threshold pressure between gel and water model during the cavitation growth come from the mechanical strength of the microfibrillar gel structure, inherent materials properties such as surface tension and viscosity of the medium, and interfacial tension between water and collagen fibril of the gel model. The mechanical Strength of Collagen at different scales has been studied, and it found that the gel-like microfibril exhibits mechanical properties comparable to collagen single coil. Therefore, the bubble growth requires additional force to deform the gel network. Furthermore, surface tension and viscosity of the medium at the nanoscale plays significant roles in cavitation dynamics, surface tension, and viscosity of the gel model is higher than the water. Finally, it is found that water and collagen fibril molecules exhibit net attractive interfacial tension in the gel model. To further quantify the extra tensile pressure, we have studied the microstructural topology of the gelatine fiber network and proposed a network strain energy-based failure model that takes into account the bubble-network interaction. The results of your proposed model are then compared with the continuum fracture model based on the critical energy release rate of the gelatine. Finally, validation is done with experimental data.</p>

Multiscale Cavitation Mechanics in Soft Materials

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

Supporting the need among researchers worldwide for additional online and multimedia content, ASME now offers the ASME Conference Video Collection. This platform will collect and provide long-term access to conference presentation videos, encompassing all technology areas within ASME's technical conference and events program. About 30,000-40,000 engineers across all mechanical engineering and related disciplines participate in ASME conferences each year. This includes authors of approximately 6,000 to 8,000 technical papers published by ASME, the majority of whom also submit video presentations for our virtual conferences. The video collection will be available as an add-on to existing product packages or as a separate subscription.