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Title:Bioinspired microvascular self-healing in polymers and composites
Author(s):Patrick, Jason
Director of Research:Sottos, Nancy R.; White, Scott R.
Doctoral Committee Chair(s):Mondal, Paramita
Doctoral Committee Member(s):Sottos, Nancy R.; White, Scott R.; Geubelle, Philippe H.
Department / Program:Civil & Environmental Eng
Discipline:Civil Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Abstract:Inspired by fluid transport in biological systems, engineered vasculature in synthetic materials provides an effective pathway to self-healing and ultimately mechanical stasis. In polymers, autonomous release of reactive chemistries from ruptured vasculature offers distinct advantages over prior self-healing approaches; largely, the capacity to achieve macro-scale fracture recovery over multiple damage cycles by replenishment of sequestered, liquid healing agent(s). Significant repair of both interfacial and internal fractures has been realized in solid polymer systems through in situ microvascular delivery. However, translation of these capabilities to load-bearing materials has been limited due to the delicate, sacrificial templates used to construct the inverse vasculatures. This dissertation outlines further development of in situ, microvascular self-healing in heterogeneous polymeric materials, particularly fiber-reinforced polymer composites, to recover fracture resistance over consecutive damage-heal cycles. A serendipitous outcome of the research is the ability to provide multi-functional properties such as active cooling, magnetic modulation, and electrical reconfiguration to otherwise quiescent, structural materials by circulating different fluids through the vasculature. Two-part, microvascular self-healing is pursued for individual constituents of a structural sandwich panel: (1) central foam core, (2) outer composite face sheets. Expansive polyurethane foam chemistry is delivered through straight, one-dimensional (1D) microchannels to heal the lightweight core material after mode-I fracture damage. The self-mixing and rapid reaction kinetics of the healing system lead to fast repair (75% in 1 h) of the macro-scale crack over repeated cycles. Precise control over delivery amount and component proportions provides a mechanism to augment healing performance. For composite face sheets, a new technique is developed around catalyst-promoted, thermal depolymerization of poly(lactic) acid (PLA) to create 3D microvascular networks within epoxy matrix fiber-reinforced composites. The vascularization approach, designated vaporization of sacrificial components (VaSC), is scalable and integrates seamlessly with current fiber composites manufacturing. Robust, sacrificial PLA monofilament is incorporated by manual and automated weaving procedures to produce pervasive vascular architectures that impart multifunctionality via simple fluid substitution within the network. A prototype, frequency-reconfigurable antenna is fabricated to demonstrate newfound electromagnetic capabilities. VaSC is also employed to create 3D, isolated and interpenetrating microvascular networks in woven fiber-composite laminates to compare in situ mixing effectiveness of a two-part epoxy/amine healing system and ensuing recovery of interlaminar fracture resistance (GIc). Unfilled networks render an increase in GIc over neat composites, while the diagonally interpenetrating vasculature achieves consistently higher healing efficiencies (> 100%) over the isolated construction for multiple cycles. Advanced microscopy and spectroscopy techniques are adapted for visualizing the internal microvascular networks and characterizing in situ healing agent distribution. Further development of sacrificial PLA is pursued to create more complex, branched and interconnected sacrificial precursors that continue to survive fiber-composite processing. Efficient procedures for uniform catalyst incorporation lower both evacuation time and residual mass in comparison to early sacrificial monofilament. Melt-spun fibers for weaving and extruded filaments for 3D printing via fused deposition modeling provide a new suite of sacrificial PLA templates. Integration of these latest precursors into state-of-the-art fiber-reinforced composites demonstrates the array of architectures and capabilities beyond self-healing that are now possible in bioinspired microvascular materials.
Issue Date:2014-11-03
Rights Information:Copyright 2014 Jason F. Patrick
Date Available in IDEALS:2017-09-29
Date Deposited:2014-12

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