Transfer Mechanisms of flame-retardant Polymer Materials in fibre-reinforced Composites: Fire Behaviour - Fire Resistance - Post-Fire Mechanics

• Applicants: Professor Dr.-Ing. Holger Ruckdäschel, since 2/2023; Privatdozent Dr. Bernhard Schartel
• Subject Area: Polymeric and Biogenic Materials and Derived Composites
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 466390889

The flame retardancy and fire resistance of composites is becoming increasingly important. A wide range of flame retardant (FRs) additives is available for non-intrinsically flame retardant polymeric matrix systems, such as the epoxy resins studied here. The selection of suitable FRs and combinations in the pure resin is already challenging, but their transfer into the fiber composite is even more complex. A fundamental understanding of the mode of action of FRs in the fiber composite compared to the pure resin and their influence on the mechanical performance before, during and after the fire event has not yet been established. The main objective of the research project is to establish knowledge-based combustion residue design for fiber reinforced composites considering structure-property relationships of the FRs used. In order to meet the enormous demands on the material, the transfer mechanisms of the flame retardants/mechanisms from the pure resin into the composite material are fundamentally investigated and evaluated with respect to their effectiveness.First, suitable FRs combinations are selected. In addition to the different classes (ceramic, glass-forming or intumescence), the particle size and size distribution of the additives also play a decisive role. The maximum adjustable upper limit of the additive mixtures in the prepreg process allows conclusions to be drawn about the optimum FRs parameters and mechanics. The first sub-objective thus represents the evaluation of the transfer properties of the resin formulations into the composite material in terms of processing, mechanics at RT and flame retardancy. The corresponding properties must be determined in the composite and in the pure resin in order to generate meaningful transfer mechanisms.An essential goal is the meaningful description of the FR mechanisms and the quantitative evaluation of their effectiveness in the fiber composite compared to the resin, as well as in the comparison of fire resistance and fire behavior. By selecting different FRs combinations, especially ceramicizing combinations of metal hydroxides and glass formers and intumescent FRs combinations, generally valid statements on the different FR concepts such as charring, flame poisoning or intumescence are expected. In the last part of the project, the influence of FRs on the mechanical properties of the composite will be evaluated. In analogy to the combustion process, where the sample can be divided into a burned and an unoccupied zone, mechanical tests will be performed. Mechanical pressure properties below and above the glass transition point of the matrix, are performed, as well as a measurement after decomposition of the matrix (post-fire). The aim of this sub-project is to establish structure-property relationships between FRs and temperature-dependent mechanical properties.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Volker Altstädt, until 1/2023