Modeling of the anisotropic thermal conductivity of fabrics embedded in a thermoplastic matrix system

Processing of thermoplastic composites is increasingly gaining importance due to their excellent mechanical properties combined with their recycling-feasibility. However, distinguishing anisotropic thermal properties of these materials make process simulation challenging. This work deals with an alternative way of analytical modeling of the anisotropic thermal conductivity of fabrics embedded in a thermoplastic matrix, as in the case of sheets for thermoforming applications, in which heating times are often process limiting. By creation of a unit cell and applying heat flux balances, the thermal conductivity in the fiber direction and in the transversal direction can be calculated. The transversal direction is the most important factor for the addressed thermoforming applications. The proposed model is then successfully validated through Hot Disk measurements of glass fiber reinforced polyamide sheets. Furthermore, authentication is reached by the comparison to measured thermal conductivity values from another study. Hence, it can be shown that the model proves to be more accurate than existing analytical models.