Fiber Alignment in Directed Carbon Fiber Preforms - Mechanical Property Prediction

A finite element method is presented for predicting the mechanical performance of discontinuous fiber mesostructures typically produced by directed carbon fiber preforming. High-filament count bundles are modeled using beam elements to enable large representative volume elements to be studied. The beams are attached to a regular grid of 2D continuum elements, which represent the matrix material, using an embedded element technique. The model is validated by comparing simulations with experimental data for random and aligned fiber architectures produced with different tow sizes ( 6 and 24 K) and fiber lengths ( 28, 58, and 115 mm). Stiffness and strength predictions are generally within 10% for 6K preforms, but this error increases up to 40% with increasing tow size because of the assumption that the fiber bundles are circular in cross-section.