Investigation of Continuously Produced Thermoplastic Honeycomb Processing - Part II: Fusion Bonding

Following paper Part I, this article investigates the last step of ThermHex process namely fusion bonding. The critical point of the fusion bonding step is to prevent catastrophic deformation (collapsing) of cell walls under heat and pressure. This demands a rapid heating rate and short heating time to keep sufficient stiffness for the inner part of cell walls against the pressure applied on the honeycomb. Hence, in this work the transient heat transfer behavior during the fusion bonding is investigated by using a finite element model for the detailed hexagonal unit cell. Furthermore, a mathematical model is developed to analyze the deformation of molten cell walls and their gradual contact to the skin strips. The experiments based on the talc-filled polypropylene material have been performed to validate the analytical model. Consequently, the optimal fusion bonding conditions can be determined to ensure good quality for the final products.