While not a new development, Boeing recently got visibility for a new video on the lightest metal structure ever made, a microlattice by its jointly-owned research unit HRL Laboratories (the former research arm of Hughes Aircraft). At 99.99 percent air, it’s light enough to balance on top of a dandelion and strong enough that an egg wrapped in the material would survive a 25-story drop. The structure may enable new lightweight aeronautical and automotive designs.
The process to create the material, which is about 250 times lighter than Styrofoam, was first achieved at HRL in 2007 by Dr. Alan Jacobsen. Using his innovative fabrication process, the HRL team was able to make a material that consists of 99.99% open volume by designing the 0.01% solid at the nanometer, micron and millimeter scales, fabricating a lattice of interconnected tubes with a wall thickness of 100 nanometers, 1,000 times thinner than a human hair.
The genesis of the material was explained by Dr. Jacob Hundley of HRL in 2012. “My colleague, Dr William Carter, who is the manager of the Architected Materials Group at HRL, puts microlattice materials in the context of large structures. For instance, prior to the construction of the Eiffel Tower in the 19th century, the largest structure built by man was the Great Pyramid at Giza in Egypt. Modern buildings, like the Eiffel Tower are incredibly light and weight efficient by virtue of their architectures. The revolutionary concept from HRL is to bring the same principles down to the materials level by designing their architectures at the nano and micro scales.”
“In effect, it’s about architecting a material to make it the most efficient: putting material only where you need it. The design philosophy is to mimic what is done on the architectural scale using existing, commercially available materials. This is the important thing for the automotive and aerospace industries: there is no need to use exotic materials; for these sectors, you just want to take existing materials that the sectors are familiar with, but engineer and architect them so that they have new, innovative properties.”
According to Dr. Hundley, microlattice materials are energy absorbing, efficient and very light. They are also formed through a rapid net-shape process, so they enable the replacement of materials, or the elimination of processes within the manufacturing life cycle with associated high costs.
He said that its true benefit to industry is that it is a material that can be designed with an open cellular architecture that enables multiple functions to be combined within the same component, including structural reinforcement and heat transfer. In this way microlattice materials become an attractive proposition to manufacturers because they combine three desirable benefits: reduced manufacturing process cost, multi-functionality and light weight.
Microlattice materials offer a significant design freedom thanks to the ability to decouple many of the stiffness and density constraints associated with conventional materials. Rather than designing around a material that has a particular property — which means that your component is going to take on a certain shape, you can now design a material to achieve that function. For an aircraft component that needs to look and perform in a certain way, the material can be designed to meet those requirements.
According to the lab any industry sector that has a requirement for lightweight multi-functional structures could be using microlattice materials, which offers a low cost, rapid production process. The growth of the polymer template that is the model for a product takes just 30-60 seconds. The time to convert to an actual metallic structure depends on the truss geometry/thickness and the type of material that is being converted, which can take longer.
HRL is equally owned by General Motors and Boeing, and both companies want lightweight multi-functional structures which absorb energy or transfer loads efficiently, but in terms of costs, loads and throughput scales, both organisations are at different ends of the spectrum.
Source: Insitute of Mechanical Engineers, Boeing and Cleantech Concepts.