Multi-layer polymer-metal laminate as fire protection for lightweight transport structures

Abstract

This study describes the development both of a new surface thermal insulation system, the experimental investigations into its fire protection mechanism and efficacy and a new thermal response modelling program. The use of multi-layer polymer metal laminates (PML) draws on the general principle common in conventional insulation methods, such as mineral-fibre and intumescent coatings, of immobilising high fractions of gas within the material and using the gas’ low thermal conductivity, harnessing the insulating effect. PMLs have the advantage over these systems in that they also form an integral part of the structure thereby contributing to the structural performance. With the view of taking this concept from laboratory scale to manufacture, material characterisation experiments were carried out to determine thermal and expansion characteristics of the PML material as these properties significantly influence fire performance. The PML FIRE model predicts the thermal response of PML-insulated substrates and was developed to take account of PML-specific effects such as expansion and foil melting. A series of small-scale fire tests were performed over wide heat flux ranges and on various PML designs, which included variations of PML ply numbers, foil thicknesses as well as the front face appearance, in order to gain insights into the PML fire protection mechanism and to validate the PML FIRE model. Fire-structural experiments on non-reactive and combustible PML-protected substrates commonly used in lightweight structures demonstrated the lower temperature transfer and the greatly improved structural resilience of the underlying substrate achieved. Good correlation of experimental and modelled temperature curves using PML FIRE has been obtained. The thermal state of specimens during heat exposure experiments up to structural failure can now be accurately predicted. Comparison of PML against other insulation methods illustrated the PML’s equivalent or superior behaviour in reducing underlying substrate temperatures and prolonging structural life during fire-structural testing.