Wallpapered safety

"Intelligent composite seismic wallpaper" is the material's full name, but its inventors refer to it simply as "earthquake wallpaper."

At first glance, the material looks like an endless placemat, which someone has woven from plastic fiber: white, finely patterned and very thin.

It's difficult to imagine that the material can protect walls from collapsing. Researchers at the Institute of Solid Construction and Construction Material Technology at the Karlsruhe Institute of Technology (KIT) claim it can do exactly that. The fine fabric is designed to support walls and distribute the powerful forces released by earthquakes across their entire surfaces and protect them from collapsing.

Absorb earthquake tremors

Here is the trick: The material must be very firm yet at the same time flexible and elastic enough to absorb the earthquake tremors. For this reason, the fabric consists of two components, according to Mortiz Urban, a co-developer and researcher at KIT: Very stiff, high-strength glass fibers, on the one hand, are woven into the wallpaper with a very thin, elastic polypropylene plastic, on the other. The fibers run in four directions, ensuring that the energy is distributed evenly.

"Cracks are much more difficult," Urban said. The earthquake wallpaper spreads the acceleration forces caused by an earthquake across a large surface, he explained. As such, they can't concentrate on weak spots in walls as they otherwise would. And should a strong earthquake cause cracks in the wall, it won't collapse. "The fibers that run across the surface straddle the cracks and close them like a rubber band," Urban said.

If the earthquake is too strong, the glass fibers can tear apart, of course. In this case, polypropylene works as backup security. It prevents stones from falling from walls. Often, clumps of rocks and collapsed walls hinder people from trying to escape damaged buildings during earthquakes.

"With the wallpaper, we can give people the necessary time they need to flee buildings or even to stabilize walls so they don't collapse," said Lothar Stempniewski, director of the Institute of Solid Construction and Construction Material Technology at KIT.

Like proper wallpaper, earthquake wallpaper can be applied to a plastered wall, which can then be either painted or decorated with normal wallpaper. Since the material is highly porous, damp walls and the resulting mould pose no problems, according to Urban. Another variant of the earthquake wallpaper allows buildings to be covered with the material from the outside. "The fabric lies pressed in the exterior plaster like a sandwich," he said.

Special adhesive

Typical wallpaper glue is not suited for fixing earthquake wallpaper. Like the wallpaper, the glue must also be rock solid yet elastic. It must firmly secure the wallpaper to the wall but also swing when an earthquake tremor hits the wall. "Typical wallpaper adhesives are either firm or elastic but not both," said Michael Engel, project direct at Bayer Earth Science.

Bayer developed a special glue for this purpose, based on polyurethane. A special feature is that within the adhesive, the chemical groups interact in a mesh network via hydrogen bonding. Bonds loosened by the tremors reform immediately at another spot but they don't tear apart.

"We have tested the fabric on a real house located on a vibrating platform," KIT researcher Urban said. The researchers erected an Italian-style stone building on a 35-quare-meter steel platform and then proceeded to shake it. Without the fiber glass reinforcement, the house would have been completely destroyed at a certain earthquake intensity.

"Because of the earthquake wallpaper, we were unable to make the building collapse," Urban said. In fact, the house withstood another earthquake test that was one and a half times more powerful.

"Our earthquake wallpaper is optimal for a medium-strong earthquake," Urban. The wallpaper, he added, is suitable only for brick buildings but not those made of concrete, which the wallpaper can't stabilize. Stronger carbon fibers are necessary for that. The German research team is already working on this material.

"The system is ready," Bayer's Engel said. The product will launch for global marketing this year. Initially, it will not be sold in home furnishing stores but rather through partners supplying home builders and craftsmen. Municipalities, particularly in earthquake regions such as Turkey, Japan and Chile, should be encouraged to deploy the material in hospitals, retirement homes and kindergartens.

More negotiations will be required in the world's poorer countries, given the price of the earthquake wallpaper, which the product's developers expect to cost more than normal wallpaper. And because the product is to be applied initially by craftsmen, their work will add further to the price. So it can be assumed that some time will pass before earthquake wallpaper becomes a mass-market product.

Author: Brigitte Osterath / jrb
Editor: Kristin Zeier