TechFront Research and Development in Manufacturing and Technology Research Team Develops New Ultralight, Ultrastiff Additive Materials A
team of researchers from Lawrence Livermore Na- tional Laboratory (LLNL; Livermore, CA) and Mas- sachusetts Institute of Technology (MIT; Cambridge, MA) has developed a new material for additive manufacturing processes that is as dense and light as an aerogel, but has 10,000 times more stiffness.
This material is described in the researchers’ paper pub- lished in a June 20 article in the journal Science. The paper, “Ultralight, Ultrastiff Mechanical Metamaterials,” outlines the development of micro-architected metamaterials that have properties not found in nature and that maintain a nearly constant stiffness per unit of mass density. The materials, the researchers say, hold promise for future use in develop- ing components used in automobiles, aircraft or space vehicles.
“These lightweight materials can withstand a load of at least 160,000 times their own weight,” said Law- rence Livermore Labs Engineer Xiaoyu “Rayne” Zheng, the lead author of the Science article. “The key to this ultrahigh stiffness is that all the micro- structural elements in this material are designed to be over-constrained and do not bend under applied load.” While most lightweight cellular materials have mechanical properties that degrade substantially with reduced density because their structural ele- ments are more likely to bend under applied load, the materials developed by the research team maintain ultrastiff
Spadaccini, corresponding author of the article, who led the joint research team. “We fabricated these materials with pro- jection micro-stereolithography.” The team’s additive micromanufacturing process involved using a micro-mirror display chip to create high-fidelity 3D parts one layer at a time from photosensitive feedstock materi- als. This allowed the team to generate materials with complex 3D microscale geometries that are otherwise challenging or, in some cases, impossible to fabricate. “Now we can print a stiff and resilient material using a desktop machine,” said MIT professor and key collaborator Nicholas Fang. “This allows us to rapidly make many sample pieces and see how they behave mechanically.”
Lawrence Livermore Engineer Xiaoyu “Rayne” Zheng studies a macroscale version of the unit cell, which constitutes the ultralight, ultrastiff material.
properties across more than three orders of magnitude in density. The observed high stiffness is shown to be true with multiple constituent materials such as polymers, metals and ceramics, according to the research team’s findings. “Our micro-architected materials have properties that are governed by their geometric layout at the microscale, as opposed to chemical composition,” said LLNL Engineer Chris
The research team was able to build microlattices out of polymers, metals and ceramics. They used polymer as a template to fabricate the microlattices, which were then coated with a thin-film of metal ranging from 200 to 500-nm thick. The polymer core was then thermally removed, leaving a hollow-tube metal strut, resulting in ultralightweight metal lattice materials.
August 2014 |
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Photo courtesy Julie Russell/LLNL
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