The U.S. Army’s timeframe for developing future vertical lift aircraft may have become shorter with the demonstration of a technique that makes a composite material stiffer and stronger when exposed to ultraviolet light. Such on-demand control of composite behavior could help accelerate the evolution of new capabilities for future rotorcraft design, performance and maintenance.

According to engineers at the U.S. Army Research Laboratory and the University of Maryland, the enhanced Control of the composite’s mechanical behavior could potentially lead to increased aerodynamic stability in rotorcraft structures. Source: U.S. Armymechanical properties with potentially low-weight penalties as enabled by the new technique could lead to nanocomposite-based structures for use in advanced rotorcraft concepts.

These composite materials were shown to become 93 percent stiffer and 35 percent stronger after five minutes of exposure to ultraviolet light. The process involves attaching ultraviolet light reactive molecules to reinforcing agents like carbon nanotubes, which 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.

Although military aircraft were the driving force behind the research, the work has the potential for multiple uses. The chemistry used in the technique could be applicable to various reinforcement/polymer combinations, opening up this approach to applications with various materials.

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, including soft in-plane tiltrotors.