Penetration Resistance of Rubber Vulcanizates

During my tenure as a Project Officer at IIT Kharagpur, I worked on studying the penetration resistance of rubber compounds using a newly developed quasi-static test. The research focused on the effects of indenter material and design, filler type and dosage, and crosslinking density on the penetration characteristics of vulcanized rubber.

The study revealed that while the material of the indenter had a negligible effect, the shape and size of the conical indenter tip played a crucial role in penetration characteristics. The research introduced the concept of a generalized penetration characteristic curve, where a change in slope indicated the fracture initiation point. Interestingly, although fracture initiation occurred earlier at higher carbon black loading, the overall penetration resistance was enhanced due to hysteresis. This finding was further validated using the impact energy method, showcasing a unique observation.

A comparative analysis between carbon black–filled and silica-filled vulcanizates was conducted. Surface morphology of specimens penetrated at different energy levels was examined through scanning electron microscopy (SEM). Additionally, a theoretical interpretation was proposed regarding the forces acting at the indenter tip and the energy required for penetration against a conical indenter.

The research found that the initiation energy for penetration had an inverse square root relationship with the Young’s modulus of the compounds. In contrast, the energy required for crack propagation was directly proportional to Young’s modulus and correlated with hysteresis loss and the frictional coefficient of carbon black–filled vulcanizates. This work contributed to a deeper understanding of the mechanical behavior of rubber compounds, with potential implications for designing more durable materials in protective and industrial applications.