Development and characterization of magnetic particle reinforced polymers for additive manufacturing processes

• Author / Creator

  Nagarajan, Balakrishnan

• Additive manufacturing enables the production of complex parts with less tooling and minimum material wastage. Polymer composites with magnetic functionality are promising for many applications like sensors, non-contact actuators and permanent magnets for electromechanical devices. The primary goal of this research work is to develop magnetic particle reinforced polymers and engineer additive manufacturing processes for manufacturing magnetic field responsive composites and permanent magnets involving hard ferrites and critical rare earth materials. Two different additive manufacturing techniques namely, stereolithography and material jetting were utilized to manufacture both isotropic and anisotropic magnetic composites. Irrespective of the additive manufacturing technique, developing magnetic polymer formulations that offer synergistic properties are a prerequisite for developing composites with engineered properties. The research study is broadly classified into four sections. The first section deals with the manufacture of isotropic magnetic field responsive composites using a stereolithography process. A commercial 3D printer with the capability of printing UV curable resins was utilized. Adopting a structured experimental framework, the curing behavior of magnetic particle reinforced formulations and dimensional variability in printed magnetic composites were evaluated. It was observed that characteristics of 3D printed magnetic structures depend on the formulation materials, 3D printing equipment and the process parameters. The second section of the study deals with the manufacture of field structured magnetic composites using material jetting additive manufacturing process. The finite element method in magnetics was used to develop permanent magnet-based particle alignment fixtures to orient ferromagnetic particles during the printing process. Directionality analysis using microscopic images was conducted to evaluate the orientation angle and count of oriented structures at specific orientation angles. Fundamental work carried out in this section enabled the development of a 3D printer with magnetic particle alignment capability. Ferromagnetic particle reinforced formulations were engineered to exhibit enhancement in low shear viscosity and time dependent viscosity recovery that enabled control of particle aggregation, particle chaining and control of microstructure distortions in the UV curable polymers. X-Ray diffraction technique was used to identify the orientation of the easy axis of magnetization in anisotropic specimens. Magnetic characterization conducted on field-structured composites exhibited enhanced magnetic characteristics along the direction of field structuring. The third section of the study entailed the manufacture of permanent magnets using magnetic particles and additive reinforced epoxy resin formulations. Modifications in rheological behavior of polymer formulations was achieved adopting multimodal magnetic particle mixtures and additive materials. Control of particle settling, modifications in rheological behavior and geometric stability were accomplished using an additive that enabled controlling the formulation behavior at different process conditions. The characterization of magnetic polymers and composites using rheometry, scanning electron microscopy, X-ray diffraction and magnetometry analyses enabled correlating of the behavior observed in different stages of the manufacturing processes. In the fourth section of the study, an acrylate based UV curable photopolymer was engineered for additional thermal cure, and permanent magnets with a filler loading of up to 80 wt% were printed using the engineered formulation. Overall, this research work broadens the capabilities for manufacturing magnetic composites with properties tailored for a multitude of engineering applications and provides a framework to understand to role of engineering material formulations to suit a wide range of processing conditions and requirements.

• Subjects / Keywords

  • Magnetically loaded polymer composites
  • magnetic characterization
  • Micro-structure control
  • Materials for energy storage systems
  • Additive manufacturing

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-324k-qj97

• License

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