A unified approach, considering three possible heating mechanisms: fiber (Joule losses) and fiber crossover junction (dielectric hysteresis and contact resistance), to identify dominant heating mechanisms during induction processing of conductive fiber reinforced composites is presented. Non-dimensional parameters were proposed to identify the relationships between heating mechanisms and process and material parameters. Parametric studies showed that junction heating mechanisms dominate fiber heating for the material systems considered, with the exception of relatively low contact resistance (< 10 3). Results for dielectric hysteresis and low contact resistance were consistent with individual models in the literature. A design map relating the three mechanisms is presented that can help identify the dominant heating mechanism, given the properties of the composite.
Thick electrode with high-areal-capacity is a practical and promising strategy to increase the energy density of batteries, but development toward thick electrode is limited by the electrochemical performance, mechanical properties, and manufacturing approaches. In this work, we overcome these limitations and report an ultrathick electrode structure, called fiberaligned thick or FAT electrode, which offers a novel electrode design and a scalable manufacturing strategy for high-areal-capacity battery electrodes. The FAT electrode uses aligned carbon fibers to construct a through-thickness fiber-aligned electrode structure with features of high electrode material loading, low tortuosity, high electrical and thermal conductivity, and good compression property. The low tortuosity of FAT electrode enables fast electrolyte infusion and rapid electron/ion transport, exhibiting a higher capacity retention and lower charge transfer resistance than conventional slurry-casted thick electrode design.
Recent work in the literature has identi ed a new heating mechanism during induction processing of carbon thermoplastic prepreg stacks: contact resistance between bers of adjacent plies. An experimental methodology has been developed to estimate the contact resistance through heating tests based on the properties of the composite and geometry of the specimen. Measured values indicate comparable resistance values at the contact region, compared to resistance in the ber direction, for AS-4 / PEI prepreg stacks under vacuum pressure. The measured values can serve as inputs for induction heating models and process models of carbon thermoplastic prepreg stacks.
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