Material modeling of long fiber reinforced thermoplastics including damage and failure
Advisors: Seelig (IfM), Sun (IWM Freiburg)


The objective of this research is to predict the material behavior of injection molded long fiber reinforced thermoplastics (LFT) in numerical finite element simulations, which is necessary for component engineering and design. When crash loading comes into focus, it is even more important to correctly predict damage and failure. This can be a challenging task when process induced locally varying fiber lengths, fiber orientations and fiber volume fractions need to be taken into account which affects the mechanical properties. The prerequisite for a successful use of this class of material is to simulate the injection molding process and provide information on FOD and fiber volume fraction to structural calculations. A macroscopic material model is developed based on an analytical homogenization procedure, where in addition plasticity and damage are considered phenomenologically. A significant and current focus of research is in analyzing damage mechanisms on the microscale using numerical unit cell models to derive qualitative damage evolution laws for the macroscopic scale. Experimental investigations are performed to characterize the macroscopic material behavior for different stress triaxialities and strain rates using particularly designed specimens. The whole process chain is simulated using the example of an industrial component.
 

 
Figure: Experiments and numerical models on different length scales focusing on
microstructure and damage mechanisms.