1.3 In-Situ Real-Time Observation of Paper and Other Materials Under Varying Displacement Rates Using Optical Microscopy (60 fps)

Understanding the microstructural evolution of paper and other materials under mechanical stress requires high-resolution, dynamic observation techniques. Specifically, to investigate the benefits of improved interfiber bonding on fiber network properties, direct observation of failure mechanisms is essential. In this showcase, we present a versatile in-situ micro-tensile testing methodology achieved by integrating a tensile stage with an optical microscope. This custom configuration enables real-time, continuous monitoring of micro-scale deformation and fracture mechanisms. The system was optimized to capture dynamic structural changes at 60/30 fps within a maximum 2 mm×2 mm field of view. To evaluate the rate-dependent behavior of the tested material, tensile tests were conducted at various applied displacement rates, starting from 0.1 mm/min. The high temporal and spatial resolution of this setup successfully captured localized phenomena such as fiber pull-out, bond failure, and crack propagation in real-time. While demonstrated here on paper specimen, this integrated approach provides a platform for advanced mechanical characterization of various materials, such as polymers, composites, or thin films, and can be coupled with Digital Image Correlation (DIC) to map localized strain fields.