Flow modelling for an anisotropic fiber reinforced fluid




University of Twente
Faculty of Engineering Technology
Chair of Production Technology
P.0. Box 217
7500 AE Enschede
The Netherlands
Room: N204 , Horstring
Phone: +31 (0)53 489 4066
Email:  w.ali@utwente.nl


This project is jointly funded by University of Twente and TPRC under the UT Impulse program.


Thermoplastic composites are increasingly being used in the aviation industry. They offer excellent specific properties and allow part manufacturing in larger series by using press forming or compression molding technologies. The latter is especially useful for parts such as clips, brackets and stiffeners of which several hundred are required per aircraft. Despite the advantages, the use of thermoplastic composites is still relatively limited. This is partly due to the underdeveloped part development process, which generally involves extensive trial-and-error procedures and heavily relies on specific manufacturer knowhow. The application of thermoplastic composites on a larger scale requires predictable and reproducible part performance after manufacturing. This can only be achieved by maturing the part development process, which in turn requires robust virtual processing tools to predict final part performance. The research  aim is to consider performance prediction for long discontinuous fiber reinforced thermoplastics as used in compression molding processes


Compression molding of long discontinuous fiber reinforced thermoplastics combines good mechanical performance with short processing times, while it also allows for a large degree of freedom in terms of part design. The process involves flow of a long discontinuous fiber reinforced thermoplastic compound. The material flow affects the fiber orientation distribution in the part, which in turn influences the distribution of mechanical properties. Prediction of the mechanical performance, therefore, requires a proper understanding of the filling behavior and its effect on fiber orientation. The development of predictive tools for material flow and resulting fiber orientation distribution is complex, as both problems cannot be decoupled; that is flow will affect the fiber orientation, while simultaneously fiber orientation will affect flow. Moreover, due to the length of the fibers, the molding compound shows anisotropic flow properties, which complicates the filling analysis.

Tools need to be developed to predict the mold filling behavior during the compression molding process. The anisotropic character of the compound gives rise to numerical locking. Efforts need to be spent to resolve this problem. Subsequent process optimization, moreover, requires robust optimization strategies in order to account for the stochastic nature of the molding compound.

Current work

At the moment the main objective is to choose an appropriate model for our problem in order to describe fiber orientation during compression molding process. Material flow will play a key part in the process. Later on the chosen model will be solved numerically. Alongside there will be some experiments that will be performed in order to understand compression molding of long discontinuous fiber reinforced thermoplastics. Numerical and experimental results will be compared in order to have a better understanding  of the effect of fiber orientation on mechanical properties.