Jörg Nickel

Natural fibre-reinforced biopolymers as construction materials - new discoveries

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.

Carbon Fiber Composite B-Rib for a Next Generation Car

Increasing environmental, economical, and social issues force future car concepts to strive for maximum efficiency. As metal designs have reached a very high level of maturity, further potentials are seen especially with extremely lightweight (carbon) fiber reinforced composites (CFRP) exhibiting high strength and stiffness, which are advantageously integrated into multi-material designs. This section focuses on improvements in weight reduction, safety and modularisation strategies for future cars. A novel Rib and Space-Frame concept incorporating carbon fiber composites is presented. Herein, an essential component replacing the former B-pillar is the B-rib, which uses a novel mechanical principle to meet the side impact crash requirements. Furthermore, using the Rib and Space-Frame concept as an example, the entire process chain of fiber composites—from materials to design, sizing, prototype manufacture, and testing—is being presented also opening up perspectives for future mass production strategies.

Structural Materials Made Of Renewable Resources (Biocomposites)

In view of the increasing shortage of resources as well as growing ecological damage, the aspects of the exploitation of raw materials and the recovery after the end of the lifetime of products have to increasingly be taken into consideration. In addition, the aspect of saving energy by means of lightweight constructions must also be regarded. The use of conventional, i.e. petrochemically-based plastics and fibre-reinforced polymers, the production process, as well as usage and recovery are often very difficult and demand considerable technical resources. An answer to solve all these problems may be provided by natural fibre-reinforced biopolymers based upon renewable resources, called biocomposites in the following. By embedding plant fibres, e.g. from flax, hemp, or ramie (cellulose fibres) into biopolymeric matrices, e.g. derivatives from cellulose, starch, shellac, or plant oils, fibre-reinforced polymers are obtained that can be integrated into natural cycles in an environmentally-friendly manner, e.g. by classic recycling, by CO2-neutral incineration (including recovery of energy), and possibly by composting.