THREE-DIMENSIONAL HEAT TRANSFER ANALYSIS OF HOT GAS TORCH (HGT)-ASSISTED AUTOMATED FIBER PLACEMENT OF THERMOPLASTIC COMPOSITES

In-situ manufacturing of thermoplastic composites using the Automated Fiber Placement (AFP) process consists of heating, consolidation, and solidification steps. During the heating step using Hot Gas Torch (HGT) as a moving heat source, the incoming tape and the substrate are heated up to a temperature above the melting point of the thermoplastic matrix. The convective heat transfer occurs between the hot gas flow and the composites in which the convective heat transfer coefficient h plays an important role in the heat transfer mechanism, which in turn significantly affects temperature distribution along the length, width, and through the thickness of the deposited layers. Temperature is the most important process parameter in AFP in-situ consolidation that affects bonding quality, crystallization, and consolidation. Although it is well known that the convective heat transfer coefficient h is not constant and has a distribution, most studies have assumed a constant value for h for heat transfer analysis, which leads to discrepancies between numerical and experimental results. It has already been shown by the authors that, unlike other studies assuming constant h value, using a distribution function to approximate the convective heat transfer coefficient h in a three-dimensional finite element transient heat transfer analysis the temperature distribution can be well predicted in thermoplastic composite parts and matches experimental data. In this study, the use of the proposed h distribution function is analysed and validated by several measuring points. Furthermore, experimental trials are carried out to validate the results from the simulation.