PhD Proposal by Sarah A. Paluskiewicz
THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Thursday, November 19, 2020
BlueJeans Video Conferencing
will be held the
DISSERTATION PROPOSAL DEFENSE
Sarah A. Paluskiewicz
"Deformation and Structure-Property Relations of Paper during Steady-State Tearing”
Paper-based products have become ubiquitous with demand for containers/packaging, medical supplies, and commodity products. A fundamental understanding of Mode I tearing in paper is useful for both the intentional fractures induced by perforation and the unintentional fracture of a web break during roll-to-roll manufacturing. Fracture mechanics and modelling have been extensively applied to the material system with some successful agreement between empirical results and theoretical projections. However, prior work has not accounted for uncontained early yielding (extensive plasticity) from this thin-sheet material nor fully described the fracture mechanisms and process.
This work will spotlight the evolution in damage accumulation of paper to steady-state tearing and the structure-property relationships that exist within the steady-state zones. We will characterize steady-state crack growth by the size, shape, and extent of the active incremental zones. Both primary and secondary incremental zones will be characterized for a more complete energetics description of the tearing process. While thin metal sheets exhibit transverse necking, paper appears to dissipate energy by rotation of the crack flanks then reversed unloading in the crack wake. In addition, the critical and offset stresses will be measured for the system's overall resistance to tearing. We will explore how the inter-fiber bonds, internal stresses, severeness of anisotropy, and material length-scales (floc size and fiber length) can affect the zone sizes and extents in steady-state. Empirical results will be translated to models by finite element analysis to broaden the applicability of our findings. This work will help to better understand how changing aspects of the structure affect the overall resistance to steady-state crack growth in paper.