Bamboo is an appealing green building option but there are limitations to the product. MIT researchers are looking for ways to engineer the grass to create a more structurally sound material similar to plywood.
In collaboration with architects and wood processors from England and Canada, the research team has been investigating the idea of slicing the stalk, or culm, into smaller pieces and then bonding them like wood composites to form sturdy blocks.
Although the effect created by using traditional bamboo can be spectacular, the material is susceptible to insect damage and its hollow, cylindrical form limits both the shape and durability of buildings that make use of it.
There are already a number of similar bamboo products in development but the MIT project intends to gain a better understanding of their behaviour so that they can be more effectively used structurally.
Very few species of bamboo have been classified, and the lack of knowledge of the material’s microstructure has impaired efforts to design efficient, optimal structural products.
“MIT’s work is very timely and has great potential to support development of the sector,” said Oliver Frith, acting director of programme for the International Network for Bamboo and Rattan.
“While bamboo has similarities to wood, the material also has very distinct properties. Although current approaches to developing structural engineered bamboo have tended to focus on mimicking engineered wood products, the future will probably lie in innovating new approaches that can better enhance the natural advantages of this unique material.”
In-depth analysis of the microstructure of bamboo has uncovered its potential for use in composite materials with stronger and denser properties than softwoods such as pine, fir and spruce. Bamboo also grows significantly faster than commonly-used trees such as pine, reaching heights of 20 metres in a matter of months.
Using electron microscopy, the MIT researchers obtained images of the bamboo microstructure and created complete, microscale cross-sections of the entire culm wall at different heights along the stalk. They gauged the stiffness and strength of the samples by performing bending and compression tests. The outer walls, they found, are particularly dense.
Using this data, a model has been developed which predicts the strength of any given section of bamboo and bamboo type which may help wood processors determine how to assemble a particular bamboo product.
“If you wanted a bamboo beam that bends, maybe you’d want to put the denser material at the top and bottom and the less dense bits toward the middle, as the stresses in the beam are larger at the top and bottom and smaller in the middle,” explained Lorna Gibson, the Matoula S. Salapatas Professor of Materials Science and Engineering at MIT.
“We’re looking at how we might optimize the selection of bamboo materials in the structure that you make.”
With bamboo growing extensively in regions where there are rapidly developing economies, Gibson said it is a good alternative material to concrete and steel but admits that the potential for the time being remains with low-rise structures and houses rather than complex skyscrapers.
Hong Kong does often use bamboo as scaffolding in skyscraper construction. The practice, however, has been banned in China.
The Big Tree Factory in Ubud, Bali is currently said to be the world’s largest commercial structure made from bamboo, sprawling across 23,500 square feet.