Jingyi Guo, 5th year Ph.D. student in Prof. Chung-Yuen Hui’s group in the department of Mechanical and Aerospace Engineering at Cornell University, recently attended the 42nd Annual Meeting of The Adhesion Society. Jingyi won the Peebles Award for graduate student research in adhesion science and then the Alan Gent Distinguished Student Paper Award.
Her research focuses on the large deformation time-dependent mechanical behavior of a self-healing hydrogel through constitutive modeling, and fracture mechanics of the hydrogel using asymptotic and finite element analyses that compare with experiments.
The selection of awardees for the Peebles award is based on abstracts submitted as contributions to the annual meeting based on timeliness and relevance to the field of adhesion, clarity in statement of the problem or research goal, and soundness of the approach. There are 7 Peebles award winners this year.
The Peebles Award winners then presented at an oral symposium during the Annual Meeting. Then based on the presentations, the Alan Gent award, sponsored by Henkel, goes to the first place. The Gent Award winner receives a cash prize in addition to the remuneration associated wit being a Peebles Award winner.
'Fracture Mechanics of a Self-Healing Hydrogel with Covalent and Physical Cross-Links'
Traditional polymers are synthesized with a single type of bond. However, recent research has shown that a combination of physical and chemical bonds can increase toughness and promote self-healing – the two properties that are prevalent in natural biological materials. It is challenging to study the mechanical properties of these materials due to large deformation and strain rate sensitivity. Here we study the fracture mechanics of cracks in a Poly(vinylalcohol) (PVA) hydrogel chemically crosslinked by glutaraldehyde and physically crosslinked by borax ions. The physical bonds are formed by interaction of borax ions with the OH groups in the PVA chains. We formulated a 3D, large deformation viscoelastic constitutive model based on breaking and healing kinetics of physical cross-links. We demonstrate this model accurately captures the rate dependent behavior of this gel under complex loading histories. The asymptotic structure of the crack tip fields is derived in closed form, and a local correspondence principle between finite strain viscoelasticity and finite strain elasticity is established. Our constitutive model is used together with a novel time integration scheme to numerically study the stress and deformation fields near the tip of a stationary crack in single edge cracked specimens. The theoretical and finite element results (3D and 2D plane stress) agree remarkably well with experimentally observed crack opening profiles. We present preliminary theoretical and experimental results for crack growth in single edge cracked specimens. Our theoretical model is able to capture the evolving crack shape during crack growth.
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