Fracture-Induced Acoustic Emissions in Gelatin

Background The ever-growing use of soft swollen (multiphasic) materials in engineering and medical applications necessitates monitoring, understanding, and modeling of their mechanical behavior. Energy-to-crack nucleation and propagation are essential in determining load-carrying capacity and toughness of such materials. Therefore, high-throughput and robust testing techniques need to be developed for measuring failure properties of soft swollen materials. Objective To address the above need, the current study seeks to investigate the acoustic emissions (AE) released from surface cracks on gelatin samples and explore links among AE characteristics and mechanical (mostly failure) properties of the tested samples. In hard materials such as ceramics, composites, and metals, localized indentation cracks generate AE energies proportional to nucleation energies. However, to the best knowledge of the authors, a correlation study between fracture and AE properties on soft swollen materials is currently missing in the literature. Methods Synchronous Multi-Point Vibrometry (MPV, non-contact) is used to obtain reliable surface wave information (referred to as AE) emitted from cracks induced by quasistatic indentations on gelatin samples. Non-contact sensing of AE from soft materials is essential in eliminating sensor attachment induced mass and stiffness effects. Results Several properties of the AE signals such as energy, duration, rise time are analyzed and correlated to quasistatic elastic and fracture properties of the gelatin samples. Conclusions Specifically, a power-law type correlation is found between AE and fracture energies is found for gelatin and compared with hard materials in the literature.