Mechanical behavior of additively manufactured polymer composite structures and interfaces

2021-9-6
Kepenekci, Mehmet
Additive manufacturing (AM) is a technology based on the layer-by-layer production of parts. Fused filament fabrication (FFF) is one of the most cost-effective and popular AM techniques for the production of polymeric structures. While the initial use of FFF was limited to thermoplastics such as PLA and ABS, recent advances enabled the printing of composite materials and structures for superior mechanical performance. Multi-material printing through dual-nozzle systems offers a unique opportunity towards this end, enabling the production of complex geometries composed of different types of polymers. The first part of this thesis investigated one aspect of these composites – the mechanical behavior of the interfaces between two polymers. For this purpose, a range of PLA-TPU interfaces were produced by FFF, and the bonding between the two domains was investigated through mechanical testing and finite element modeling. The results demonstrated that the poor adhesion between the polymers can be significantly improved through the design of interlocking structures. Another common approach to the printing of composite structures by FFF is the utilization of polymer-matrix filaments with reinforcements. Short carbon fiber reinforced polyamide (PA-CF) is among the most promising composite filaments due to its excellent properties. While the mechanical characteristics of this specific composite have been widely studied, the corresponding performance of lightweight cellular structures made of PA-CF is not well known. The second part of this thesis investigated the mechanical performance of a wide range of cellular structures made of PA-CF through compression testing and high-speed imaging. The results show that cellular PA-CF structures provide a great combination of high strength and lightweight. The findings of the thesis show that FFF-produced composites offer great potential for load-bearing applications in a wide range of industries. Further optimization of the polymer-polymer interfaces will enable the reliable application of multi-material printing in load-bearing applications. The additional characterization of the PA-CF cellular structures will focus on their impact performance and will further expand the applications of FFF technology towards the design and manufacturing of energy absorbing structures.

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Citation Formats
M. Kepenekci, “Mechanical behavior of additively manufactured polymer composite structures and interfaces,” M.S. - Master of Science, Middle East Technical University, 2021.