This on-demand control of composite behaviour could enable a variety of new capabilities for future Army rotorcraft design, performance and maintenance.
ARL research engineer, Dr Frank Gardea said the focus of the research was on controlling how molecules interact with each other. He said the aim was to “have them interact in such a way that changes at a small size, or nanoscale, could lead to observed changes at a larger size, or macroscale.”
Dr Bryan Glaz, chief scientist of ARL's Vehicle Technology Directorate added: “An important motivation for this work is the desire to engineer new structures, starting from the nanoscale, to enable advanced rotorcraft concepts that have been proposed in the past, but were infeasible due to limitations in current composites. One of the most important capabilities envisioned by these concepts is a significantly reduced maintenance burden due to compromises we make to fly at high speeds.”
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 that sees the interaction between the reinforcing agents and the polymer increase, making the material stiffer and stronger.
The researchers said the chemistry used here is generally applicable to a variety of reinforcement/polymer combinations thereby expanding the utility of this control method to a wide range of material systems.
Dr Zhongjie Huang, a postdoctoral research fellow at the University of Maryland, said: “This research shows that it is possible to control the overall material property of these nanocomposites through molecular engineering at the interface between the composite components. This is not only important for fundamental science but also for the optimisation of structural component response.”
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, like soft in-plane tiltrotors. In addition, controllable mechanical response will allow for the development of adaptive aerospace structures that could potentially accommodate mechanical loading conditions.
“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,” said 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.”