Understanding the microstructure of fiber-filled polymeric melts during manufacturing processes
Thijs Egelmeers defended his PhD thesis at the Department of Mechanical Engineering on February 20th.
The use of short fiber-reinforced polymeric materials has increased significantly in recent years. These composites are used in everything from automotive parts to consumer products because they are lightweight yet incredibly strong. Next to that, manufacturing costs are low for these materials, and they can easily be used to form complex shapes by using conventional processing techniques. The challenge with these processing techniques is that they determine the orientation and alignment of the tiny fibers within the material and that influences the performance of the material. Thijs Egelmeers explores in his PhD research how fibers move, rotate and align as polymer composites flow during manufacturing processes. The findings from this research lay the foundation for more accurate predictions of the microstructure of short fiber-reinforced polymeric materials formed during composite processing.
In conventional polymer processing techniques like injection and compression molding, which are used a lot to make complex shapes with fiber-filled polymeric melts, the composites are subjected to a combination of shear and extensional flows. Though, the current models that are typically used in the industry are unable to accurately predict the orientation and alignment of fibers within short fiber-reinforced polymeric materials in complex flows or at high fiber volume fractions. In his research combined innovative lab experiments and computer simulations to be able make predictions more accurate. For the experimental approach he chose a unique method which involved light scattering to observe the fiber orientation in real-time while stretching and shearing the composite. Additionally, powerful computer models simulated the fibers’ movements at a microscopic level.
Research findings
A surprising finding within this research is that a lot of factors, like the speed of deformation or the elasticity of the polymer, have little effect on how quickly fibers rotate and align when the short fiber-reinforced polymeric material is initially in a completely relaxed state. Simple models can predict the orientation behavior of materials in this state. However, when stresses in the material are developed, the fibers rotate more slowly. This phenomenon was successfully captured using a refined model.
Foundation for accurate predictions
The findings that resulted from this research contribute significantly to a deeper understanding of the complex interplay between fiber orientation and the deformation and flow of the material in processing of short-fiber reinforced polymer composites. This facilitates more accurate predictions of the microstructure which are formed when a composite is processed. In turn, those predictions improve the ability to forecast the mechanical performance of products made with short fiber-reinforced polymeric materials.
Research School: EPL
Title of PhD thesis: Promotor: Prof. Ruth Cardinaels and Prof. Patrick Anderson. Co-promotor: Dr. Nick Jaensson.