Wood can do more
The Fraunhofer WKI combines various materials into high-performance building elements using minimal material and energy. These novel hybrid material systems are designed to conserve resources, protect the climate, and at the same time expand the scope for architectural design.6 Mar 2023
The Fraunhofer Wilhelm-Klauditz-Institut (WKI), headquartered in Braunschweig, Germany, has been dedicated to wood research and sustainability through the use of renewable raw materials for more than 75 years. One of the most pressing questions at present - given that eight percent of global greenhouse gas emissions are caused by cement production - is how to build in a way that is as resource-efficient, cost-effective and aesthetically pleasing as possible. To find out, researchers at the Fraunhofer WKI are combining different materials to create high-performance building elements using minimal materials and energy.
Basically, the research is based on the properties of the wood. In relation to its weight, it has high strength and also offers high adaptability and workability. This is contrasted by the rather variable properties of wood in terms of tensile and compressive strength, which means that its use in load-bearing structures in particular has been limited to date. To compensate for this drawback, the WKI is developing both suitable fiber composite plastics and the appropriate manufacturing processes for wood-fiber composite plastic systems (wood-FRP systems). One approach, for example, is to incorporate multiple layers of polymer matrix and reinforcing fabric into a wooden structure as a tensile component. Several processes are available for implementing this technology. For example, a particularly high quality and reproducibility can be achieved by vacuum infusion. The hand lay-up process, on the other hand, allows in-situ applications, whereby the fiber composite plastic can even be used to reinforce existing wooden structures, provided the wooden components are accessible.
Another approach is wood-concrete composite systems (HBV systems), intended as an alternative to reinforced concrete. According to the WKI, they are particularly suitable for use under bending loads, in which high tensile stresses can occur on the underside of the composite system, for example in beams or ceiling slabs. To absorb these tensile forces, the Braunschweig researchers replace the steel with suitable wood. In this way, ceiling slabs are created, for example, in which a beam structure is first installed with a top layer of wood-based panels. The top layer is an integral part of the construction and also serves as formwork and possible support for the ceiling. It is coated with an adhesive and then filled with fresh concrete. While the concrete layer ensures high strength in the compression zone, the wood takes over the tensile forces that occur. In the composite, this not only results in high flexural strength, but also saves a large proportion of tensile reinforcement and concrete compared with reinforced concrete floors. In addition, HBV-Systems facilitate processing on the construction site, because in contrast to conventional construction methods, the formwork no longer has to be removed after the concrete has cured.
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