Modelling decomposition and fire behaviour of small samples of a glass‐fibre‐reinforced polyester/balsa‐cored sandwich material

Abstract

This publication presents the experimental and numerical methods to model the devolatilization process of a glass‐fibre‐reinforced polyester/balsa‐cored sandwich material on small scale. The fundamental modelling of the source term in pyrolysis‐based fire simulations requires as input data the thermochemical properties of solid fuel and the kinetic parameters of the devolatilization process. First, the thermal decomposition of both elements composing the sandwich structure was studied by thermogravimetry coupled with gas analysis, in air and pure nitrogen atmospheres at several heating rates, in order to define a comprehensive multi‐step reaction pathway. A differential equation system is defined to model these decomposition processes. The kinetic parameters were then estimated by solving the system of equations by an inverse problem. Second, the fire behaviour of each element was studied separately and then combined in the sandwich structure on the cone calorimeter. In addition, numerical simulations with Fire Dynamics Simulator were performed to gradually assess the ability of the model(s) to reproduce each element composing the sandwich structure. Numerical and experimental results are compared and then discussed. Overall, the model provides a good agreement with the experimental data and encourages to model higher scales. Copyright © 2012 John Wiley & Sons, Ltd.

Modelling Reaction-to-fire of Polymer-based Composite Laminate

“…It shows that the ignition time decreases slowly with increasing oxygen content and this is because more oxygen is available to react in the flame with the devolatilization products of thermoset matrix. Marquis et al (2011) have shown for a thermoset-based sandwich composite that when the inlet oxygen level is close to 10 %, the decomposition rate of solid phase is halved compared to the ambient level. The slowest of the mass loss rate with O 2 depletion is the result of the reduction of oxygen diffusion processes in the solid phase.…”

“…Nevertheless, it is often necessary to use a combination of methods to understand the occurring processes. Some simplifications can be defined to hypothesize that the behaviour observed with measurement instruments is caused mainly by the mechanism of decomposition and is not very much influenced by external noise [Bustamante-Valencia (2009), Marquis et al (2011]. Generally, these researches are carried out for various heating rates β and two atmospheres (pure nitrogen and air).…”

“…They are generated based on the hypothesis that each peak of the mass loss rate curves in thermogravimetry represents a reacting species in the solid phase [Ohlemiller (1985), Rein et al (2006)]. As an example, a reduced comprehensible kinetic mechanisms for polyester resin was found by Marquis et al (2011), as shown in Table 1. It was defined in accordance with the chemistry of the thermal process.…”

“…Velocity of the CO formation depend of the type of hydrocarbon, the temperature, the local concentration in O 2 and the residence times. A variety of other gases can be produced during the combustion of composite material [Hume (1992), Sorathia (1993), Tewarson (1993), Sastri et al (1999), Marquis et al (2011)]. The amount of gaseous products and the diversity of the species can be influenced by: (1) the composition of the matrix; (2) the reinforced fibre and architecture; (3) the geometry and orientation of the composite; (4) the decomposition processes (char formation, delamination, crack...); and (5) the fire conditions (oxygen content, pressure and temperature).…”

“…The amount of gaseous products and the diversity of the species can be influenced by: (1) the composition of the matrix; (2) the reinforced fibre and architecture; (3) the geometry and orientation of the composite; (4) the decomposition processes (char formation, delamination, crack...); and (5) the fire conditions (oxygen content, pressure and temperature). For a given composite, the analysis of Marquis et al (2011) shows that the kinetics of mass loss and production of species depend on the oxygen concentration and the incident radiant heat flux on the material (or ambient temperature). The depletion of oxygen concentration leads to an increase of unburnt, namely: CH 4 , C 2 H 4 and HCOH.…”