US Army Research Laboratory develops technique for adaptive composite materials

Engineers at the US Army Research Laboratory (ARL, Adelphi, MD, US) and the University of Maryland (College Park, MD, US) announced April 17 that its engineers have developed a technique that causes a composite material to become stiffer and stronger on-demand when exposed to ultraviolet light. This on-demand control of composite behavior could enable a variety of new capabilities for future Army rotorcraft design, performance and maintenance.

ARL research engineer Dr. Frank Gardea says the focus of the research is on controlling how molecules interact with each other – to have them interact in such a way that changes at a nanoscale, could lead to observed changes at a larger size.

"In our lab at UMD we have been developing unique carbon nanomaterials and chemistry, but it was not until Gardea approached us did we become aware of the intriguing challenge and opportunity for reconfigurable composite materials," says Dr. YuHuang Wang, professor of the Department of Chemistry and Biochemistry at the University of Maryland. "Together we have achieved something that is quite remarkable."

The technique consists of attaching ultraviolet light reactive molecules to reinforcing agents like carbon nanotubes. These reactive reinforcing agents are then embedded in a polymer. Upon ultraviolet light exposure, a chemical reaction occurs such that the interaction between the reinforcing agents and the polymer increases, thus making the material stiffer and stronger – the research determined the composite materials could become 93% stiffer and 35% stronger after a five minute exposure to ultraviolet light.

"The enhanced mechanical properties with potentially low weight penalties, enabled by the new technique, could lead to nanocomposite based structures that would enable rotorcraft concepts that we cannot build today," says Dr. Bryan Glaz, chief scientist of ARL's Vehicle Technology Directorate.

Future structures based on this work may help lead to new composites with controlled structural damping and low weight that could enable low maintenance, high speed rotorcraft concepts that are currently not feasible – soft in-plane tiltrotors, for example. In addition, controllable mechanical response will allow for the development of adaptive aerospace structures that could potentially accommodate mechanical loading conditions.