Construction materials from renewable resources - state of the art and future potentials

Kurzfassung

Originally coming from aerospace technology, fibre reinforced plastics (FRP) are successfully used for various applications, today because of their excellent specific properties, e.g. high strength and stiffness, low weight and the potential of optimisation by orientating (esp. Continuous) fibres along the load paths. In order to successfully meet the environmental problems of these classic composites, the DLR Institute of Structural Mechanics developed an innovative idea in 1989: By embedding natural and near natural reinforcing fibres e.g. flax, hemp, ramie, cellulose etc. into a biopolymeric matrix from cellulose, starch or lactic acid derivatives etc. (thermoplastics as well as thermosets), new fibre reinforced materials, called biocomposites, were created and are still being developed. In terms of mechanical properties being comparable to glass fibre reinforced plastics (GFRP), latest developments on new fibre/matrix combinations and environmentally compatible flame retardants enable biocomposites to replace GFRP in most cases. Biocomposites are designed to meet the processing requirements for commonly used manufacturing techniques, e.g. pressing, injection moulding, filament winding, BMC, SMC etc. Apart from anisotropic and specially tailored lightweight structural parts with continuous fibre reinforcements, biocomposites are very well suited for panelling elements in cars, railways and aeroplanes, etc. using different kinds of nonwovens from single fibres (needlefelt nonwovens, fleeces etc.) to be easily adapted to the usually curved shapes of panellings, fairings etc. When modifying the resin systems more or less extensively, biocomposites can be designed for different applications either to be stable or biodegradable. Apart from re-use or recycling, this offers additional options of a convenient removal after the end of the lifetime, i.e. combustion of any kind of biocomposites now being carbon dioxide neutral and completely slag-free, or biodegradation or composting of the biodegradable kinds of biocomposites. Thus they are fully integrated into natural cycles and can also meet the steadily increasing environmental demands of legislative authories.