Much work has been accomplished since the discovery that particles in a dielectric fluid experience forces when placed in an electric field, including mathematical descriptions of the forces and resulting motion of particles of differing shapes, particle separation and segregation for use in drug delivery, and even the manipulation of long-chain molecules of certain polymers.

The initial FALCom Processing Apparatus.
Recently, researchers at the University of Wisconsin-Madison developed a technology called Field-Aided Micro- Tailoring (FAiMTa) that uses a liquid polymer solution containing nano- to micro-sized particles that is cured in the presence of an electric field. This produces a solid structure with fillers aligned in a particular direction, according to the orientation of the electric field.

The research presented here builds upon the FAiMTa technology in the design of a processing system that allows for nano- to micro-scale fillers to be aligned and oriented in a liquid photopolymer solution before being locked in place by the laser curing of the photopolymer matrix. The Field-Aided Laminar Composite (FALCom) processing technology is the realization of this research. Using FALCom processing, fillers are aligned into pseudo-fibers that can be arranged by design. Systems can then be designed with structural, thermally conductive, or electrically conductive fillers for multifunctional applications that will allow for the production of three-dimensional composites for structural, electrical, or heat sink applications.

A combination of properly controlled electric fields and accurate material selection can lead to functionally graded composite materials with locally tailored filler modifications by design. The experimental FALCom process has shown the capability to fabricate multilayered particulate reinforced polymer composites with controlled filler orientation. It has been shown that the selected fillers can be aligned in order to create pseudo-fiber support structures. In future experimentation, these structures may be used for structural, electrical, or thermal manipulation of a polymer composite.

This work was conducted to facilitate a proof of concept for the FALCom technology, and therefore a limited number of specimens were fabricated for each sample set. In the future, an indepth study will be conducted into the mechanical properties of FALCom fabricated composite structures. Preliminary results from mechanical characterization of the composite samples with the bidirectional alignments have shown to increase the flexural modulus by up to 24% over those with randomly oriented fillers. Photoelastic response of FALCom specimens will also be evaluated in the future.

The work was conducted with a benchtop version of the FALCom processing technology, with a fabrication envelope of approximately one cubic inch. A large-scale FALCom machine is being constructed currently that will have a working volume of approximately one cubic foot. This machine will be used to determine if the technology is applicable for the fabrication of three-dimensionally reinforced rapid prototype composites, and will continue to support research and analysis of micro-composites.

This work was done by Larry R. Holmes, Jr. of the Army Research Laboratory. ARL-0153

This Brief includes a Technical Support Package (TSP).
Micro-Composite Fabrication via Field-Aided Laminar Composite Processing

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This article first appeared in the June, 2013 issue of Defense Tech Briefs Magazine.

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