A Non-Isothermal Process Model for Consolidation and Void Reduction during In-Situ Tow Placement of Thermoplastic Composites

In in-situ composites processing, heat and pressure are applied locally to composite tows to achieve consolidation. During the consolidation of thermoplastic composite tows or plies, a modest amount of flow takes place. Due to the high viscosity of thermoplastics, the fibers and the matrix move together. We propose a novel approach to model this process-approximate the medium as a compressible viscous continuum rather than use Darcy's law which has been successful in modeling thermoset composites processing. The void content of the composite changes during the consolidation process due to various mechanisms. A consolidation model for thermoplastic composite that incorporates—the relevant void growth and transport phenomena has been developed. The model is capable of predicting the final void fraction and the final thickness of a composite part as a function of the processing speed and the consolidation pressure under non-isothermal conditions.