A NONISOTHERMAL 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 locall y to composite tows to achieve consolidation. During the consolidation of thermoplastic composite tows or plies, a modest amount of flow tak es place. Due to the high viscosity of thermoplastics, the fibers and the matrix move together. We propose a novel approach to model this pr ocess-approximate the medium as a compressible viscous continuum rathe r than use Darcy's law which has been successful in modeling thermoset composites processing. The void content of the composite changes duri ng the consolidation process due to various mechanisms. A consolidatio n model for thermoplastic composites that incorporates the relevant vo id growth and transport phenomena has been developed. The model is cap able of predicting the final void fraction and the final thickness of a composite part as a function of the processing speed and the consoli dation pressure under non-isothermal conditions.