This study presents computational analysis of the complex dynamics observed in chemically blown polyurethane foams during reaction injection molding process. The mathematical formulation introduces an experimentally motivated non-divergence free setup for the continuity equations which reflects the self expanding behaviour observed in the physical system. The foam growth phenomena which is normally initiated by adequate pre-mixing of necessary reactant polymers, leading to an exothermic polymerization reaction, bubble nucleation, and gas formation, is captured numerically. We assume the dependence of material viscosity on the degree of cure/polymerization, gas volume fraction, and temperature as well as nondependence of mixture density on pressure. The set of unsteady nonlinear coupled partial differential equations describing the dynamics of the system are solved numerically for state variables using finite volume techniques such that the front of the flow is tracked w ith high resolution interface capturing schemes. Graphical representation of the foam volume fraction, evolution of foam heights, and temperature distributions is presented. Results from our simulations are validated with experimental data. These results show good quantitative agreement with observations from experiments

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In consideration of environmental aspects and limited availability of resources, the focus of automotive and aerospace industry lies on significant weight optimisations especially for moving loads. In this context, innovative lightweight materials as well as material combinations need to be developed. A considerable potential for lightweight structures can be found in fibre- or textile-reinforced semi-finished products. Due to their specific characteristics and extraordinary structural diversity, thermoset and thermoplastic matrix systems can be used. In particular, carbon fibres as reinforcing components combined with a thermoplastic matrix polymer are able to create new high-performance applications. Besides the significant lightweight characteristics of the fibre-plastic-composites, in some instances contrary requirements must be satisfied in many areas, such as strength and ductility. In this field, the combination of fibre-reinforced polymers with aluminium or titanium sheets creates unique composite materials, so called hybrid laminates, which fulfil the unusual expectations.The focus of the current study lies on the development of a new thermoplastic hybrid laminate named CATPUAL (CArbon fibre-reinforced Thermoplastic PolyUrethane/ALuminium laminate). The structure of the laminate is an alternating sequence of thin aluminium sheets (EN AW 6082-T4) and fibre-reinforced thermoplastic polyurethane (TPU). The individual layers are consolidated to each other by using a hot pressing process. First results showed that the impregnation capability of thermoplastic polyurethane surpasses any other commercially available hybrid laminates. Furthermore, the mechanical properties regarding bending strength and interlaminar shear strength are exceeding the state of the art drastically.

In the present article, the polymer melt impregnation of textile fiber reinforcements in an injection molding process is explored theoretically and experimentally. Simplifying the numerical simulation of the thermoplastic melt flow behavior a specific mold with integrated single-glass fiber bundle was developed and used for experimental fill studies with thermoplastic melt. The polymer melt impregnation of the fiber bundle in the injection molding process is modeled and calculated with Complex Rheology Polymer Solver (CoRheoPol), a simulation tool developed at Fraunhofer Institut fAr Techno- und Wirtschaftsmathematik by the present authors. Navier-Stokes and Navier-Stokes-Brinkman equations are used to describe the melt flow in a pure fluid region and porous media, considering the non-Newtonian flow behavior of thermoplastic melts. Experimental and numerical results are compared determining the filling fronts and fiber impregnation of the injection molded test samples. A clear relationship between the degree of impregnation, verified by magnified photomicrograph, and the position of flow front can be detected. A good correlation of simulated and experimental flow fronts against the degree of filling of the mold is observed too. The differences in macroscopic flow behavior between the cavity with and without an integrated fiber bundle with respect to the impregnation process can be simulated with high accuracy