Master of Engineering Science
Mechanical and Materials Engineering
Fraunhofer Institute for Chemical Technology
Composite materials are widely used in the automotive industry to keep cost and weight down. The ability to simulate the fabrication of parts is an important way to use resources effectively. The molding process can also have very dramatic effects on material properties. These properties are determined by the microstructure of the polymer composite material, including the length, concentration, and orientation of the fibers used as reinforcement. Therefore this study seeks to characterize the material properties of a long glass fiber reinforced polyamide composite, the effects of molding conditions on those material properties, and characterization of the microstructure of the polymer composite under different processing conditions. It was found that material flow affects fiber orientation, including simple geometry changes, and that this material had an inherent fiber alignment from the initial state. Fiber length and concentration throughout the polymer composite part was found to be very consistent under all processing conditions investigated.
Summary for Lay Audience
Composite materials have become a staple for the automotive industry. One method of composite fabrication that is very effective for light and strong semi-structural parts is compression molding, where a material is formed into a shape using heat and pressure. For effective use of time, money, and materials, being able to simulate compression molding is greatly desired. A successful simulation needs a variety of input parameters relating to the material properties. Some of the key properties include the fiber volume concentration, fiber length, and fiber orientation, which are part of the materials microstructure. In addition, there is interest in understanding how the various molding conditions will affect those properties due to material flow, mold and material temperatures, and part geometry.
This study aims to characterize the microstructure of two simple parts: a plaque and a hat section. Both parts have been compression molded using Lanxess Tepex Flowcore, a glass-fiber/polyamide-6 composite. The reason that simple parts are being characterized is to provide a baseline for simulation validation, and to be able to isolate differences in molding conditions such as having the material undergo significant flow, but with no geometry changes.
The results show that fiber length remains very consistent regardless of molding conditions, and that part geometry influences the microstructure, specifically the fiber orientation. It was also found that the initial unmolded material has an inherent fiber alignment.
Clement-Thorne, Broderic, "Material Characterization of Compression Molded Composites" (2022). Electronic Thesis and Dissertation Repository. 8423.
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