A sample of a co-continuous polymer composite material produced in the lab by a team including MIT postdoctoral researcher Lifeng Wang. Device in background is used to test the strength of the material. (Credit: Melanie Gonick)
A team of researchers at MIT has found a way to make complex composite materials whose attributes can be fine-tuned to give various desirable combinations of properties such as stiffness, strength, resistance to impacts and energy dissipation.
composites is a “co-continuous” structure of two different materials with very different properties, creating a material combining aspects of both. The co-continuous structure means that the two interleaved materials each form a kind of three-dimensional lattice whose pieces are fully connected to each other from side to side, front to back, and top to bottom.
The research — by postdoc Lifeng Wang, who worked with undergraduate Jacky Lau and professors Mary Boyce and Edwin Thomas — was published in April in the journal Advanced Materials.
The initial objective of the research was to “try to design a material that can absorb energy under extreme loading situations,” Wang explains. Such a material could be used as shielding for trucks or aircraft, he says: “It could be lightweight and efficient, flexible, not just a solid mantle” like most present-day armor.
In most conventional materials — even modern advanced composites — once cracks start to form they tend to propagate through the material, Wang says. But in the new co-continuous materials, crack propagation is limited within the microstructure, he says, making them highly “damage tolerant” even when subjected to many crack-producing events.
Some existing composite materials, such as carbon-carbon composites that use fibers embedded in another material, can have great strength in the direction parallel to the fibers, but not much strength in other directions. Because of the continuous 3-D structure of the new composites, their strength is nearly equal in all dimensions, Wang says.
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