A team led by the U.S. Army’s Combat Capabilities Development Command’s (CCDC) Army Research Laboratory (Aberdeen, Maryland, USA) is conducting a set of theoretical research experiments through computer modeling. They say their initial findings show that polymers filled with carbon nanotubes could potentially improve how unmanned vehicles dissipate energy.
“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,” says Yelena R. Sliozberg, a computational materials scientist at the laboratory.
According to the research team, segmented polyurethane urea elastomers exhibit versatile physical and mechanical properties. So in their study, the researchers used computer modeling to look into the specific nature of these materials.
Sliozberg explains that hierarchical composites are a promising area of research for the Army vehicles as they are less susceptible to corrosion, which can lead to early component death.
“In contrast to traditional thermoset composites, performance polyurethane-urea elastomers are far less brittlem and they offer unparalleled control over material architecture,” Sliozberg says. "Carbon nanotube/polymer composites have desirable electrical and thermal characteristics that exhibit behaviors superior to conventional fiber materials.”
Sliozberg says the researchers need to have deeper understanding of the nature of molecular-level interactions in these materials in order to enhance the maximum stress levels that the material can withstand, as well as tailor energy dissipation mechanisms.
Chemical modification of nanofillers is nontrivial and can typically diminish properties by changing the structure and chemistry, she explains. For example, the Young modulus could be lower.
According to the researchers, their results strongly indicate the effectiveness of incorporation of aligned carbon nanotubes for microstructure optimization, as well as at the interface without any filler surface modification.
“It shows that the presence of high affinity of polyurethane 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 polyurethane urea nanocomposites hierarchical composites,” Sliozberg says.
Based on their research, future Army vehicles could see an improvement in their structural materials by making them lighter weight and less susceptible to corrosion, along with having higher electrical conductivity than traditional elastomers. The materials also show great potential to protect vehicles against static buildup 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,” Sliozberg says. She adds that there is “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 components.”
In a related study, collaborators at Drexel University (Philadelphia, Pennsylvania, USA) are investigating potential uses of polyurethane urea polymers with carbon nanotubes as filament materials for three-dimensional printing. However, the Army laboratory says it is not currently conducting these studies on any vehicles. The researchers say they plan to collaborate with other Army teams for testing in the near future.
Source: U.S. Army, www.army.mil.