Process Behavior of Short Glass Fiber Filled Systems during Powder Bed Fusion and Its Effect on Part Dimensions

In powder bed fusion of polymers, filled systems can provide a wide range of part properties, which is still a deficit in additive manufacturing, as the material variety is limited. Glass fiber filled polymers provide a higher strength and stiffness in parts; nevertheless, the process behavior differs from neat polymer systems. In this study, the optical properties and their effect on the part dimensions are analyzed. A higher glass fiber content leads to an increased absorption of laser energy, while the specific heat capacity decreases. This results in larger part dimensions due to higher energy input into the powder bed. The aim of the study is to gain process understanding in terms of ongoing mechanisms during processing filled systems on the one hand and to derive strategies for filled polymer systems in powder bed fusion on the other hand.

To Problem of Filler Failure in Processing of Fiber-Reinforced Materials

Filled polymers seem very promising materials for production. Polymers can be filled with a variety of diverse materials, be it polycaprolactam fiber, glass fiber, or steel wire. Compared to their non-filled counterparts, filled composites have a number of advantages. Production of filled polymers can be challenging due to the processing equipment (the rubber mixer, rollers, and extruders) mixing the fiber with the polymer matrix. In their purest form, polymers mostly don’t have the desired properties, which is why special additives (fillers, plasticizers, dyes, stabilizers, etc.) must be added to obtain the desired functional properties. This is why composites account for an ever greater share of polymers.

Use of Dynamic Mechanical Analysis (DMA) for Characterizing Interfacial Interactions in Filled Polymers

Dynamic mechanical analysis (DMA) provides reliable information about the viscoelastic behavior of neat and filled polymers. The properties of filled polymers are relevant to different industries as protective organic coatings, composites etc. Interfacial interactions in filled polymers play an important role in determining their bulk properties and performance during service life. In this brief review article, studies that used DMA to characterize the interfacial interactions in filled polymers have been reviewed. The available open literature provides a mixed opinion about the influence of interfacial interactions on the glass transition temperature of filled polymers. Nevertheless, it appears that in the case of strong interfacial interactions between the filler particles and the polymeric matrix, the peak value of tan δ is reduced in comparison to that of a filled polymer where these interactions are weak.