Experimental observation and modeling of fiber rotation and translation during foam injection molding of polymer composites

We investigated the interactions between dispersed carbon fibers and growing cells in high-pressure foam injection molding experiments using a polystyrene/carbon-fiber/carbon-dioxide system with an in-situ visualization technique. We found that the fibers exhibited both translational and rotational displacements in close proximity to the growing cells. Their rotational and translational displacements were measured quantitatively using visualization snapshots. These were found to be a strong function of the cell size, the initial cell-fiber distance, and the initial fiber angle. We developed an analytical model to describe the instantaneous fiber orientation and location as a function of the corresponding cell size and the fiber's initial orientation and location. The theoretical predictions were in a good agreement with the experimental results. This showed the model's accuracy in predicting the fiber displacement. Our research provides a deeper understanding of the mechanisms through which foaming influences the percolation threshold of conductive polymer composites. (C) 2016 Elsevier Ltd. All rights reserved.