Micromechanical modeling of discontinuous long fiber reinforced composites

The performance of discontinuous fiber composites is intricately linked to the microstructure of the composite material. Therefore, micromechanics prove valuable for the analysis and design of these materials. Two micromechanics theories, the high fidelity generalized method of cells and Carrera Unified Formulation, are used to model a repeating unit cell (RUC) of the Tailorable Universal Feedstock for Forming, a highly aligned discontinuous fiber carbon fiber composite system. The models are evaluated for their ability to predict the effective properties and local stress fields within the RUC. The stress fields between the fiber ends and the fiber-matrix interfacial stresses are of particular interest. The models are used to predict the effective properties of single fiber and multiple fiber RUCs with varying fiber-to-fiber end gap lengths, as well as the local stresses in the fiber and matrix. Both models produced similar results and demonstrated that they could capture the complex local load transfer. A statistical study is also undertaken to understand the effect of gap clustering on the effective properties and local stress fields.