[LUM#7] The wood that will shape tomorrow
The oldest material in the world is now considered one of the most modern. A renewable natural resource, wood offers extraordinary mechanical qualities. And it is by far the most eco-friendly of materials...
Furniture, transportation, construction, civil engineering, aeronautics, and even robotics: visible or hidden, rustic or high-tech, solid or processed, it's everywhere! Is wood making a big comeback? It's only just beginning, promises Bernard Thibaut, a researcher at the Laboratory of Mechanics and Civil Engineering (LMGC). And with good reason: "like metal and polymers, it is one of those universal materials that can be used to make just about anything," says , a researcher who has been studying the biomechanics of trees and the properties of wood for 40 years (Wood machining with a focus on French research over the last 50 years, in Annales des sciences forestières, 2016).
Reference material
This material, as old as humanity itself, has nevertheless undergone a recent eclipse. Humans have extensively practiced an "all-wood" lifestyle: since their appearance on Earth, almost everything around them has long come from the generosity of trees. This reached its peak in the18th century: a golden age when wood became a universal material, invading the human sphere more than ever before.
Then came the industrial revolution and the triumph of competitors: the19th century was the age of steel, the20th century that of concrete and plastic. And the21st century? It is the age of a renaissance in wood, says Bernard Thibaut. "Wood took a long time, but it has finally made its transition to modernity. This timeless material of choice is now being rediscovered thanks to the technological advances it benefits from."
New industrial uses
If wood is making a comeback, it is in new forms, confirms Cédric Montero. "Historically, raw wood has been used for a very long time," summarizes this researcher specializing in structural wood at the LMGC. The current boom in wood, particularly in construction, is largely due to new processing methods: plywood, glued laminated timber, cross-laminated timber, products that make use of wood chips or sawdust , such as particleboard or fiberboard..." (Feasibility of glued laminated beams made from tropical hardwoods, B. Thibaud, 2013)
A revolution. By breaking free from the limitations of its original form, wood has moved from craftsmanship to the industrial era. It can now be used for all kinds of purposes. This reconstituted wood is "comparable to a fiber composite," continues the researcher: a standardized, reproducible material. Used today even in high technology, it offers excellent mechanical performance: it is every bit as good as its artificial cousins, fiberglass, carbon fiber, and Kevlar... over which it has one major advantage: its lightness, due to its microscopic honeycomb structure.
The current trend is to combine wood with these same materials or with others—steel, for example—in composites whose structure depends on the desired results. The result is performance that is far superior to that of each of the individual components. "This is a field with vast potential: we are only at the beginning, with many technological innovations still to come."
Strong, lightweight... and fire-resistant!
Man's oldest ally is proving to be a promising material, capable of turning any industrialist into a staunch wood lover. "Recent innovations have brought about a real revolution in attitudes," notes Bernard Thibaut. Building quickly, thanks to prefabricated modular structures? The lightness of wood makes it possible. Building huge towers? It's possible! The race for height is on: new industrial materials derived from wood can support buildings exceeding 20 stories. And they offer ideal performance in terms of seismic constraints...
Wood construction, which has been relatively uncommon in France until now for cultural reasons, is gaining ground. "Attitudes towards this material have changed, particularly in terms of fire risk: just a few decades ago, it was unthinkable to build large structures out of wood. Its fire resistance is now being reevaluated." Less heat-conductive than steel or concrete, wood burns slowly without warping or releasing toxic substances.
Eco-friendly fiber
The greatest asset of wood lies elsewhere: this product of the forest is resolutely eco-friendly. Abundant and under-exploited—particularly in France, which has thefourth largest forest area in the European Union—wood is a renewable and inexpensive resource that requires little energy to process. And while the manufacture of steel, concrete, aluminum, and plastic produces greenhouse gases, wood can help reduce them: trees naturally capture and trap carbon dioxide (CO2), a gas responsible for global warming, at a rate of one ton per cubic meter. CO2 is removed directly from the atmosphere... and all that remains is to store it in the form of wooden furniture or buildings. Wood is making a big comeback against a backdrop of sustainable development: using it as a material helps combat the greenhouse effect. It's unavoidable.
30,000 different species
"There are at least as many types of wood as there are tree species—more than 30,000 species worldwide! Each has its own properties, which can vary by a factor of 1 to 100 depending on the variety," explains Bernard Thibaut. The best approach is to combine different species for the best results. This practice is particularly relevant in construction. Even in its raw form, wood, a protean material, offers an extraordinary range of possibilities. As for its mechanical properties, they are "necessarily" of great interest (Physical and mechanical properties of reaction wood, in The biology of reaction wood, 2013): "Let's not forget that wood built a tree, which is a particularly daring structure: few architects would dare to attempt this type of construction!"
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