AFRL and University Partners Used 3D Printed Composite Materials to Make Structural Parts

The Air Force Research Laboratory (AFRL), located at Wright-Patterson Air Force Base (WPAFB) near my hometown of Dayton, Ohio, has long been interested in using 3D printing and composite materials for the purposes of aerospace applications. Last year, AFRL’s Composites Branch at the Materials and Manufacturing Directorate partnered up with researchers from the University of Arkansas, the University of Miami in Florida, Louisiana Tech University, and the University of Texas at El Paso (UTEP) to work on advancing 3D printable composite materials.

The Composites Branch works on the research and development of organic and ceramic matrix composite technologies for legacy, developmental, and future Air Force system components. Together with its university partners, the AFRL branch demonstrated 3D printed composite materials, made from a combination of carbon fiber and epoxy, which had been successfully fabricated and used to make structural parts on both air and space craft. The results of this 3D printed composite material effort will soon be published in a special issue of the Journal of Experimental Mechanics that’s dedicated to the mechanics of 3D printed materials.

Dr. Jeffery Baur, leader of the Composite Performance Research Team, said, “The potential to quickly print high-strength composite parts and fixtures for the warfighter could be a tremendous asset both in the field and for accelerating weapon system development.”

Composite materials are made up of two, or sometimes more, constituent materials that have very different chemical or physical properties. When combined, these components produce a new material that has characteristics which are different from the originals. The individual components that make up the composite will remain distinctly separated within the final material structure.

When compared to the more low-quality polymers that are typically used in 3D printers, the composite materials demonstrated by AFRL and its partners are the same type that are already being used to make Air Force system components. These materials are very strong, while also lightweight, and have higher thermal and environmental durability than most.

Most traditional epoxy and carbon fiber composites are made by layering carbon fiber sheets, coated with epoxy resin, on top of each other. Then, the whole thing is cooked for hours in a costly pressure cooker to finish. The major downside to this method is that it’s more difficult to create parts that have complex shapes when sheets are being used.

This is where additive manufacturing comes in. Composite materials that are 3D printed are able to create parts with those complex shapes, and additionally don’t require the use of long heating cycles or expensive pressure cookers. On a materials level, there aren’t a whole lot of downsides to using composites for the purposes of producing, assembling, or repairing parts for the Air Force, whether at the depot or out in the field.

Military branches in other countries are also seeing the benefit of 3D printable composite materials. For example, engineers in India are manufacturing complex core structures using the composite 3D printing process; when combined with top and bottom face sheets, these structures will create lightweight sandwich structures that have properties tailored specifically to, as AFRL put it, “the physical forces that need to be carried.”

Conventionally fabricated sandwich structures use the same core geometries over the entire area of an aircraft skin, but a 3D printed version would be able to stand up under heavier forces when necessary, while also remaining lightweight in other parts of the skin.

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