Degree Type

Dissertation

Date of Award

2018

Degree Name

Doctor of Philosophy

Department

Aerospace Engineering

Major

Engineering Mechanics

First Advisor

Wei Hong

Second Advisor

Ashraf Bastawros

Abstract

Soft materials and structures are very common in our daily life and industry products, but still shows great potential on many innovative applications. To make better use of them, we need a good understanding of the fracture and deformation of the materials. Starting from soft elastic foams, this paper proposes a scaling law for the fracture energy of soft elastic foam by using the analogy between the cellular structure and the network structure of rubbery polymers. To verify the scaling law, a phase-field model for the fracture processes in soft elastic structures is developed. The numerical simulations in two-dimensional foam structures of various unit-cell geometries have all achieved good agreement with the scaling law. Inspired by the toughening mechanism of double-network (DN) hydrogels, a highly stretchable soft composite and a magnetic double-network composite capable of large recoverable deformation were fabricated. Just as the DN gels, the coexistence of the partially damaged and intact regions resulted in a stable necking in the composite when subjected to uniaxial tension. The propagation of the necking zone corresponded to a plateau on the stress–stretch curve. The experimental observations serve as a good evidence of the fracture process of DN gel. Finally, a phase field model for the fracture of DN gel is proposed. The numerical results are compared with transformation toughening results since the mechanical behavior of both material shows great similarity. The process zone shows similar pattern with what we observed in DN composite experiments.

Copyright Owner

Zhuo Ma

Language

en

File Format

application/pdf

File Size

104 pages

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