Phase selective flame-retardant laminates

Fibre-reinforced polymer composites are widely used in structural applications due to their lightweight and high strength. However, their poor fire performance–particularly the flammability and softening of the polymer matrix at elevated temperatures–poses a significant safety concern. This thesis explores three strategies to enhance the fire performance of polymer laminates through structural optimisation and material innovation. The first approach involves applying external protective coatings to carbon fibre-reinforced polymer (CFRP) laminates using three configurations: cellulose nanofibres CNF/clay nanocomposite papers, commercial intumescent coatings based on expandable graphite, and vermiculite-based nonwoven mats. These coatings delayed the onset of mechanical failure under fire by acting as thermal barriers, reducing heat transfer and promoting char formation. Bench-scale fire resistance tests showed significantly prolonged failure times and reduced heating rates. The second strategy addresses the limitations of coating adhesion by applying flame retardants (FRs) directly into the top layer of the laminate based on this same polymer - polybutylene terephthalate (PBT), which provides strong interfacial bonding between layers. Three potentially synergistic FR systems – Boehmite/Melamine poly(zinc phosphate) (AlOOH/MPZnP), Aluminium diethylphosphinate/Melamine cyanurate (AlPi/MC), and Expandable graphite/Melamine polyphosphate) (EG/MPP) – were selected to enhance fire performance. Concentrating FRs in the top layer offers fire protection while reducing the total FR concentration in the laminates. Thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA-FTIR) revealed synergistic effects in decomposition behaviour, particularly in the AlOOH/MPZnP system. This was further supported by the superior performance of this laminate in cone calorimetry, which showed reduced peak of heat release rate (pHRR) and maximum average rate of heat emission (MARHE) values, indicating lower fire hazards. The third approach introduces protective interlayers – such as WHIPOX ceramic composite, titanium foil, rubber insulation mat, and sustainable fibre mats within CFRP laminates. The front section of CFRP laminate, with two strategically placed interlayers, acted as sacrificial and insulative barriers, extending the time to failure up to tenfold. The combination of Ceramic layer and titanium foil proved most effective, while bio-based mats (hemp/basalt) offered comparable fire resistance, demonstrating eco-friendly alternatives. Microstructural damage, such as delaminations and bucklings, was analysed via X-ray CT to understand failure mechanisms. Overall, this study presents that laminate design – encompassing material selection, targeted flame retardant incorporation, and structural configuration – has a critical influence on the fire performance of fibre-reinforced polymer composites. The investigation of three innovative fire protection strategies provides valuable insights for future material development and design.

Author dc:creator

• Tabaka, Weronika

Advisor dc:contributor.advisor

• Auhl, Dietmar

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Identifier URI

https://doi.org/10.14279/depositonce-24019

OAI identifier oai:identifier

oai:depositonce.tu-berlin.de:11303/25197