Multi-Material Properties via Multi-Field Processing on a Single Constituent Set

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This grant will support research that will contribute new knowledge enabling the processing of polymer matrix composites with controlled heterogenous architectures that possess spatially varying mechanical and electronic/magnetic properties throughout the structure. The work extends the range of materials and structures accessible via additive processing techniques promoting the progress of science and advancing national prosperity. Almost all modern materials consist of a mixture or composite of materials which can act synergistically to produce interesting and useful properties which do not exist in any of the constituents. The research looks to the simplification of these additive processing techniques by applying external electrical and magnetic fields during the manufacturing process that leads to a spontaneous internal ordering of the two phases. While state-of-the-art multi-material additive manufacturing utilizes complex machinery and separate reservoirs for each material, this process would simplify manufacturing by fabricating parts with a range of material properties from a single material reservoir. Such processing has the capacity to revolutionize additive manufacturing by fabricating fully functioning devices through the control of the micro-architecture of the composites and hence their material properties. The work will seek out material and processing condition pairings that can achieve dichotomous properties, allowing the source material to produce materials that are stiff or compliant, magnetic or non-magnetic, conducting or insulating, etc. as needed locally during component fabrication. For example, instead of needing conducting metals surrounded by insulating polymer to fabricate parts with integrated wiring, this work will determine specific processing techniques to produce locally conductive and insulating regions within the part from the single material reservoir. Structured polymer matrix composites which are critical to a wide range of industries including aerospace, automotive, and healthcare developed through additive manufacturing would simply product development and open new application areas benefiting the U.S. economy and society. The outreach and educational components of the work will help broaden participation of underrepresented groups in research and positively impact engineering education in an emerging field. The goal of this research is to experimentally and theoretically study and quantify the ability of uniform and non-uniform electromagnetic fields and their gradients to develop micro-architectures in polymer matrix composites that have not been achieved using traditional uniform and single field processing. An electromagnetically assisted manufacturing process can provide a viable, lower-cost route to multi-material properties by reducing the complexity of these manufacturing systems down to a set of process variables that lead to desired properties. Externally applied electric and magnetic fields act orthogonally on the embedded barium hexaferrite particles within the uncured composite due to the particles' planar shape and crystallographic c-axis magnetization, allowing multi-axis control of particle alignments. Furthermore, externally induced dielectrophoretic and magnetophoretic particle-particle interactions allow control of the arrangement of aggregates of particles, providing a second hierarchical level of control. While dielectrophoresis and magnetophoresis are well known phenomena, this research will provide new knowledge of how regulated interactions of both fields with anisotropic particles can be used to develop micro-architectures that produce extremum dielectric, magnetic, and mechanical properties. The research team will perform computational multi-physics simulations of the electromagnetic field processing to predict resulting micro-architectures. Finite element modeling of the resulting micro-architectures will then provide estimates of resulting material properties. Experimental fabrication of these composites using predicted process variables, combined with an array of electromagnetic and mechanical characterization, will be used to refine simulations and to direct iterative experimental and computational trials, closing the loop with a multi-level Monto-Carlo optimization scheme. Results of this work will provide data on the process parameter, constituent, effective property design space that others may use to fabricate materials with tailored properties in a general electromagnetic processing context.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.