Methodology to establish a forming process window for thermoset aligned discontinuous fiber composites

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Highly aligned discontinuous fiber composites have been pursued with the goal of achieving high performance properties with the formability of short fiber composites. The feedstock consists of a highly aligned discontinuous fiber preform which can be combined with thermoplastic or thermoset resins to create prepreg that can extend in the fiber direction. With this added benefit of lamina extensibility in the fiber direction, a methodology is needed to determine the degradation of material quality with applied forming strain. A framework is established to define a forming process window which sets the optimal process conditions—temperature and strain rate—for maintaining lamina uniformity after deformation. Digital image correlation was used to measure strain uniformity for samples stretched in uniaxial tension at constant temperature and strain rate. The experimental results show that forming strain rate should increase with increasing process temperature. The process window established in this work will be used to ensure that material uniformity can be optimized in manufacturing trials and other material characterization evaluations.