COMBOO may very well be a new approach for green core materials for sandwich applications. COMBOO is a honeyCOMB structure made of bamBOO. It consists of bamboo rings arranged in a honeycomb pattern and a top and bottom layer made of different types of wood and plywood.
Bamboo is an extremely fast growing grass. Growth rates of up to 1 meter per day were reported. It is native to all continents except Europe and Antarctica. Over 1000 different species can be found on earth. Bamboo has a density of approximately 0.6 – 0.7 g/cm3 considering the solid material only. Tensile strength, hardness and bending capabilities are also very high. Asian countries have been using bamboo and derived products for ages in a more traditional way as building materials, for weapons, furniture, household equipment and accessories, cooking material and even for scaffolds for skyscrapers.
The concept of COMBOO is to use the bamboo in a nearly unmodified way, to preserve its superior properties and to reduce necessary machining steps. At around 0.22 g/cm3 the density of COMBOO is significantly lower than that of the solid bamboo material itself considering that the honeycomb structure consists of over 70 % of air.
The sandwich panels investigated in a PTJ-funded project enable CO2 savings through reduced material usage on the one hand and rapid CO2 sequestration in regions of the world where a lot of CO2 is produced on the other. Furthermore, the low transport weight due to the lower density of the new material also significantly reduces the amount of CO2 produced during transport. In addition to the lower density all other properties of conventional CLT panels, in particular the structural and thermal insulation properties, remain the same or can even be improved. This means that more living space can be created by adding storeys and thereby increasing the capacity of existing buildings, as the mass of the new walls is smaller and therefore the load-bearing capacity of the existing building fabric is better utilized.
This paper gives an overview of possible bamboo based honeycomb like core structure applications in civil engineering and timber architecture.