A continuum approach for consolidation modeling in composites processing

During composite processing, consolidation refers to the application of pressure and/or temperature cycle to the fiber preforms and the uncured liquid resin to increase the fiber volume fraction. The goal is to eliminate voids before the resin solidifies. Consolidation process involves two stages. In the first stage voids are filled and reinforcement compressed due to the application of pressure. Elevated temperatures facilitate this by reducing the viscosity of the resin. In the second stage, the resin cures and the structure solidifies. This paper describes the modeling approach for the first stage of the consolidation process. Governing equations are presented for reinforcement deformation, resin redistribution and porosity evaluation and a semiimplicit numerical scheme well suited to handle complex material models is formulated to track the evolution of part properties during the consolidation process. The applicability of the model is demonstrated with the help of two diverse examples: (1) Consolidation of prepreg facesheets during co-cure of a sandwich panel and (2) Corner consolidation during autoclave processing of a prepreg-based panel. The effects of geometry (such as radius of curvature) and materials (such as initial porosity) are discussed.