Fire-resistant and Bio-based Fibre Reinforced Plastics for Structural Lightweight Construction

Due to their lightweight construction potential, fibre reinforced plastics (FRP) are used in particular in the aerospace and automotive industries and, to an increasing extent, in rail vehicles and shipbuilding. As lightweight construction materials, such fibre reinforced plastics have the potential to improve for instance the eco-balance of ships. If they are based on renewable raw materials, the carbon footprint can be reduced very effectively.

Integrating these materials as structural components is not state of the art and requires new concepts, for instance in shipbuilding, writes Katharina Koschek of the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in the journal ‘Technical Textiles’. The guideline ‘Interim Guidelines for use of fibre reinforced plastic (FRP) elements within ship structures: fire safety issues’ is the basic requirement for the use of FRP in ships and the subject of the research. Currently, integrated structures or non-structural parts that do not contribute to the strength of the ship can be replaced by fibre reinforced plastics. This is where the ‘GreenLight’ project of the Fraunhofer Institute in Bremen comes in: There, bio-based fibre composites are to be developed for load-bearing components that also meet the high fire safety standards.

Fire Safety for Structural Elements

Temperature resistance and fire behaviour are highly dependent on the organic polymer matrix. Under the influence of heat, thermal decomposition of the polymer occurs through pyrolysis processes, whereby the decomposition temperature, the gases produced, their flammability and toxicity are decisively influenced by the chemical structure of the polymers used. Therefore, particularly high fire protection requirements must be met here.

Polybenzoxazines show promising properties with regard to the necessary preventive fire protection and are characterised by lower heat release rates, lower smoke gas density and toxicity in case of fire. Even without the use of halogenated flame retardants, they show great potential to meet the necessary fire protection requirements in various application areas.

With this approach, the reaction to fire of fibre reinforced plastics can also cope with the requirements for mechanical deformation of components due to collisions or accidents – and further lightweight construction potential can be tapped in the future.

Focus on Sustainability

The Bremen researchers’ “GreenLight” project will analyse sustainable benzoxazine-based composite materials in terms of sustainable chemistry. Within the framework of a sustainability analysis, special attention will be paid to ecological and social factors in the selection of raw materials (origin, production, etc.).

Such high-performance plastics have a high value-added potential and should therefore be in future recycled in the sense of material upgrading in alternative applications. Recycling existing materials or even components reduces the use of raw materials – but this presupposes that the components are used in materially pure components.

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