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" Mechanics of Soft Networks and Network Based Composites at Finite Deformation "
Islam, Mohammad Refatul
Picu, Catalin R.
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Latin Dissertation
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English
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| Record Number
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1105801
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TLpq2325355330
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| Main Entry
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Islam, Mohammad Refatul
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Picu, Catalin R.
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| Title & Author
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Mechanics of Soft Networks and Network Based Composites at Finite Deformation\ Islam, Mohammad RefatulPicu, Catalin R.
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| College
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Rensselaer Polytechnic Institute
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| Date
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2019
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2019
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| Degree
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Ph.D.
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| Page No
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143
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| Abstract
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Fibrous materials, biological or engineered, are predominantly comprised of a random fiber network like microstructure. These materials exhibit significant nonlinear behavior that essentially originates from microscopic network architecture. In addition, most network based materials naturally occur as composites, in which the mechanics is tuned by complex interactions of inclusions and the underlying network. A precise knowledge of the micromechanics of fiber networks as homogeneous or composite systems is therefore crucial for the understanding of the mechanical behavior of network based materials. The objective of this thesis is to establish structure-property correlations for homogeneous and composite network systems subjected to finite deformation. In particular, this dissertation focuses on two model systems, representatives of engineered and biological materials respectively. Mycelium, a fungal biopolymer network, is studied as an engineered system and subsequently, mycelium based particulate composite is investigated. As a second model system, biological networks with or without embedded inclusions are studied in the context of soft tissue mechanics. Mycelium is the root of fungi that can be engineered to develop self-growing material. Our experimental results show that mycelium is a linear elastic material in small strain. At large strain, it exhibits strain hardening in tension whereas the material mimics cellular foam behavior in compression. Under cyclic loading, mycelium also exhibits strain dependent hysteresis and stress softening effect. Based on our experimental results, a multiscale model consisting of a microscale fiber network representation coupled with a macroscale stochastic continuum model is developed and validated to predict the mechanical behavior of mycelium. A phenomenological damage model is implemented to predict stress softening behavior under cyclic loading. For mycelium based particulate composite, we observed that the composite behavior is mycelium matrix dominated and largely insensitive to filler size and aspect ratio. The composite also exhibits significant hysteresis and gradual stress softening behavior under cyclic compression. A homogenization based numerical model is developed and validated for overall behavior of mycelium based particulate composite when subjected to compression loading. A key advantage of the model is that it efficiently incorporates the constitutive behavior of the fibrous mycelium matrix phase based on the multiscale model of pure mycelium. In the second part of this thesis, we focus on biological networks and aim to unravel the role of network structural parameters in defining the tissue characteristics such as strain stiffening and Poisson contraction. We consider three dimensional (3D) discrete network models with cellular and fibrous architectures and show that cellular networks undergo more pronounced strain stiffening and lateral contraction compared to fibrous networks. The two architectures exhibit different types of strain hardening and different dependence of the small strain elastic modulus on network parameters. It is concluded that the differences are due to the more pronounced heterogeneity and kinematic constraints of the fibrous networks. In terms of reinforced biological networks, it is observed that inclusions induce drastic transition from bending to stretch dominated deformation in the network by confinement effect. Reinforcement induced by rigid or soft inclusions is controlled by the type of base network where reinforcement is dramatically more pronounced for low density, sparsely crosslinked and bending dominated networks. In broader terms, the findings of this dissertation will enhance fundamental understanding of fiber network mechanics and will offer scientific rationale for the design of novel fiber network materials.
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Materials science
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Mechanics
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