PLAN 86: Article
A New Approach To Assembling Big Structures

A Potential Revolution in the Construction of Buildings and Bridges

Researchers at SA+P’s Center for Bits and Atoms have developed a lightweight composite material that could revolutionize the assembly of buildings and bridges and other large structures such as airplanes and spacecraft, dikes and levees. The new approach is described in the August 15 issue of Science, co-authored by postdoc Kenneth Cheung and Center director Neil Gershenfeld.

Made from tiny interlocking parts that can be snapped together much like the bricks of a child’s construction toy, the chainmail-like composite is ten times stiffer than existing lightweight materials so that pound-for-pound less of it is needed to carry a given load – a factor that could greatly reduce the costs of construction and assembly while allowing greater design flexibility.

The mass-produced parts can easily be disassembled and reassembled to repair damage, or to recycle the parts into different configurations, and the team is now developing an assembler robot that can crawl, insect-like, over the surface of a growing structure, adding pieces one by one.

Although this new material is made by linking many small components – and structural failures in traditional composite manufacturing typically start in the joints between components – it behaves like an elastic solid, with a stiffness equal to that of much heavier composites, because forces are distributed through the lattice-work inside the pieces.

What’s more, when conventional composite materials are stressed to the breaking point, they tend to fail abruptly and at large scale. But this new modular system tends to fail only incrementally, making it more reliable and more easily repaired.

Furthermore, there is no risk of the pieces falling apart on their own because, like the buckle on a seat belt, they are designed to be strong in the directions of forces applied in normal use and require pressure in a different direction in order to be released.

The possibility of linking multiple types of parts introduces a new degree of design freedom into composite manufacturing. Combining different part types can result in structures that bend in different ways in response to loads – instead of moving only at fixed joints, for instance, the entire arm of a robot or wing of an airplane could change shape.

In addition to Gershenfeld and Cheung, the project included alumna Sarah Hovsepian (SM’12, Architecture), now at NASA’s Ames Research Center, and Joseph Kim, an undergraduate student in electrical engineering and computer science. The work was supported by the Defense Advanced Research Projects Agency and the sponsors of the Center for Bits and Atoms, with Spirit Aerosystems collaborating on the composite development.

This piece is based on a story by David L. Chandler of the MIT News Office.