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Title:Microvascular composites as a multifunctional material for electric vehicles
Author(s):Pety, Stephen J
Director of Research:White, Scott R
Doctoral Committee Chair(s):White, Scott R
Doctoral Committee Member(s):Sottos, Nancy R; Geubelle, Philippe H; Braun, Paul V; Evans, Christopher M
Department / Program:Materials Science & Engineerng
Discipline:Materials Science & Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Microvascular composites
Multifunctional materials
Battery cooling
Thermal imaging
Computational fluid dynamics
Crashworthiness
Carbon fiber
Abstract:Electric vehicle (EV) batteries require both thermal regulation and structural protection. A novel form of battery packaging is proposed to accomplish this multifunctional objective using microvascular fiber-reinforced composites. Batteries are sandwiched between carbon fiber/epoxy panels containing embedded microchannels. Coolant flow enables active cooling while the composite material provides strength, stiffness, and crashworthiness at low weight. Several studies are performed on the cooling performance of microvascular panels. First, thermography experiments and computational fluid dynamics (CFD) simulations are used to characterize the cooling performance of carbon/epoxy panels with straight 500 µm diameter microchannels. Panels with high enough channel density and coolant flow rate can sufficiently cool batteries below 40 °C for applied heat fluxes up to 1000 W m-2. Next, experiments and simulations are performed on carbon/epoxy panels with more complex 2D microvascular networks (parallel, bifurcating, serpentine, and spiral networks). The spiral network offers optimal thermal performance at high pumping pressure (>100 kPa), while the bifurcating network and a computationally optimized parallel network offer slightly reduced thermal performance at much lower pumping pressure (<10 kPa). In a collaborative effort, gradient-based optimization is used to improve the blockage tolerance of microvascular networks. Optimizations are performed on networks with different nodal degree (a measure or redundancy) to minimize temperature while the network is subject to a blockage. Tests on microvascular silicone panels confirm that optimized networks with high nodal degree experience minimal temperature rises when blocked. Finally, crush tests are performed on microvascular carbon/epoxy panels to demonstrate how channels affect composite crashworthiness. Corrugated panels are fabricated containing 400 µm channels at different spacing (10 mm and 1.2 mm), orientation with respect to the load (transverse and longitudinal), and orientation with respect to surrounding plies. Crush tests revealed no significant reduction in specific energy absorbed (SEA) for all test cases. Further tests demonstrate that microchannels can actually improve composite crashworthiness by triggering stable, energy-absorbing failure modes in flat panels.
Issue Date:2017-04-17
Type:Thesis
URI:http://hdl.handle.net/2142/97373
Rights Information:Copyright 2017 Stephen J. Pety
Date Available in IDEALS:2017-08-10
Date Deposited:2017-05


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