Kevlar
Kevlar bullet proof vests.
Polymer fibres such as Kevlar and Nomex are well known for their use in defence applications, namely in the production of protective clothing for soldiers in conflict zones, but scientists have to continue developing polymer fibres to ensure they can protect the infantry from the weaponry of the future, which are certain to be much more sophisticated and deadly.
The Army Research Laboratory (ARL) in the US has been tasked with designing new polymers for superior protection capabilities and it is starting by unravelling the complex relationship between polymer chemistry, microstructure and energy absorption.
ARL is currently working on polymer fibres - the next-generation of polyamides such as Kevlar or polyethylenes like Spectra - that can withstand extremely ballistic environments. The research team is investigating polymers at a molecular level under high rate loading conditions at the ARL-established Enterprise for Multiscale Research of Materials, which is currently making breakthroughs that are allowing the team to model polymers at high strain rates, pressures and temperatures. This work will ultimately allow the team to design ultra high molecular weight polyethylene - the core constituent for Dyneema and Spectra.
ARL researchers Dr Jan Andzelm and Dr Tanya Chantawansri together with Professor Mark Robbins of Johns Hopkins University are leading the research to clarify mechanisms associated with polyethylene using atomistic simulations and coarse-graining methods. The key to modelling this system is the development of reactive potentials to be used in the atomistic modelling of Ultra-High Molecular Weight Polyethylene. The team has successfully achieved this by using accurate quantum mechanical data to find our atomistic potential.
Prof Robbins explained: "This potential is unique and its development was made possible by combining the expertise in state of the art electronic calculations at ARL with the complementary experience at JHU on classical models of polymers."
Dr Andzelm added: "These potentials are general enough to be applied to many materials and will help in the advancement of other materials too, such as graphene and other novel 2D polymers."
Valid computational models are pivotal to the team's work. The data the researchers generate provides valuable input to the computational models, but when it comes to complex systems such as ballistic fibres, the production of appropriate model systems can prove a challenge. ARL's new in-house Center for Advanced Polymer Processing is a state-of-the-art facility with extremely controlled processing conditions that can provide these model systems as well as complex fibres with advanced performance based on computationally predicted relationships between chemistry, microstructure and performance.
Once researchers understand the processes of how these materials respond to ballistic simulations, ARL believes "the parents of soldiers in 30 years' time can be rest assured that ARL has provided the scientific foundation to protect them to the fullest extent".