Army researchers are studying new polymer composites for use in unmanned vehicle systems, such as the RQ-7B Shadow shown here, because the composites are lightweight, less susceptible to corrosion and have higher electrical conductivity than traditional elastomers. Photo: Master Sgt. Matt Hecht.Using computational modelling, a team led by researchers at the Army Research Laboratory of the US Army's Combat Capabilities Development Command has discovered that polymers filled with carbon nanotubes could potentially improve how unmanned vehicles dissipate energy. The researchers report their discovery in a paper in Polymer.
"Our motivation for this research is that there could potentially be a use, as matrix material, for incorporation into lightweight composites in unmanned vehicle systems," said Yelena Sliozberg, a computational materials scientist at the laboratory.
Polyurethanes are versatile polymers used in a broad variety of applications, including coatings, foams and solid elastomers. As film adhesives, for example, they are commonly used as bonding agents between layers of glass and as polymer back layers in the transparent glass or plastic composites used as side windows in tactical vehicles. In particular, high-performance segmented poly(urethane-urea) (PUU) polymers exhibit versatile physical and mechanical properties.
In this study, the team used computer modeling to look into the nature of these materials. According to Sliozberg, hierarchical composites are a promising area of research for Army vehicles, as they are less susceptible to corrosion, which can lead to early component death.
"In contrast to traditional thermoset composites performance, poly(urethane-urea) elastomers are far less brittle and they offer unparalleled control over material architecture," Sliozberg explained. "Carbon nanotube/polymer composites have desirable electrical and thermal characteristics that exhibit behaviors superior to conventional fiber materials."
Sliozberg said that a deeper understanding into the nature of molecular level interactions in these composite materials is needed in order to enhance the maximum stress levels they can withstand and to tailor their energy dissipation mechanisms. This team's results strongly indicate the effectiveness of incorporating aligned carbon nanotubes to optimize the microstructure of hierarchical PUU polymers in the matrix and at the interface.
"It shows that the presence of high affinity of poly(urethane-urea) to carbon nanotubes would lead to a novel green synthesis pathway without the need of any surface functionalization of nanotubes for fabrication of carbon-nanotube-reinforced poly(urethane-urea) nanocomposites hierarchical composites," she said.
Future Army vehicles could see an improvement in their structural materials since these composites are lightweight, and are less susceptible to corrosion and have higher electrical conductivity than traditional elastomers. They also show great potential for protecting vehicles against static build-up and discharge, and lightning strikes.
"Certain military vehicles such as Army helicopters must withstand intense vibration and fatigue, and the conductive nature of these materials could lead to an unprecedented level of multifunctionality with potential in real-time structural health monitoring through embedded strain sensing and damage monitoring that will lead to safely and accurately assessing the remaining life in vehicle components," Sliozberg said.
Collaborators at Drexel University are furthering this research by investigating the potential uses of PUU polymers with carbon nanotubes as filament materials for 3D printing. The researchers also plan to collaborate with other Army teams for testing in the near future.
This story is adapted from material from the US Army Research Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.