Numerical and experimental investigation of mechanical properties of parts manufactured via carbon fiber reinforced material extrusion

Date

2024-8

Author

Süre, Akıncan

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With the improvements in manufacturing technology, it is possible to produce light parts with complex geometries with additive manufacturing today. This brings critical advances in many industrial fields, such as aerospace, defense, and automotive, where the weight of the parts is crucial. A new material extrusion process, continuous fiber fabrication (CFF), has been developed by an industrial company, namely Markforged, which enables the design of composites with fiber reinforcement in the material extrusion process. CFF process includes two types of reinforcements: isotropic and concentric. In isotropic reinforcement, the parts' interior is reinforced continuously with fibers, while concentric reinforcement allows the strengthening of the design locally, such as reinforcement of outer shells or regions around the holes where high stresses are usually encountered. The latter one, concentric reinforcement, is investigated in the scope of this thesis. One of the challenging problems regarding CFF is the mechanical performance measurement of the parts under certain loading cases. Although testing is usually the preferred way of evaluating mechanical performance, it is not always possible or feasible. Hence, finite element analysis (FEA) should be considered as an alternative way of measuring the mechanical responses of the parts. However, one should be meticulous about the accuracy and validity of numerical analysis. Even though there are many studies in the literature about the evaluation of the mechanical performance of CFF parts with FEA, there are many discrepancies between research. Hence, in this thesis, a finite element modeling strategy for parts manufactured with CFF is developed, and the modeling technique is verified with tests. First, required material characterizations are performed in order to obtain material properties for selected materials. Then, three specimens having different loading conditions, tensile, bending, and eccentric loads, are designed and manufactured. Later, specific load cases are created, and tests are performed. Finally, corresponding numerical models for tests are prepared, and FEA simulations are run to validate the numerical modeling approach. The validation criterion is based on the force and displacement of the parts for their elastic behavior. The results of the numerical models and tests are in good agreement with each other for lower displacement values since FE analyses are done with linear and elastic material properties. For higher displacements, where the mechanical response of the parts is plastic, there are discrepancies between numerical analysis and test results. The sources of errors are discussed in the thesis in order to develop better mathematical modeling techniques in the future.

Subject Keywords

Additive manufacturing, Continuous filament fabrication, Composite materials, Finite element analysis, Material characterization

URI

https://hdl.handle.net/11511/111021

Collections

Graduate School of Natural and Applied Sciences, Thesis