Abstract
In this work, the fire reaction properties of flax-polypropylene (PP) composites were investigated at multiple sample angles both experimentally and numerically under two different heat flux conditions (35 and 50 kW/m2) in the cone calorimeter environment. An innovative testing setup which can accommodate a wide range of angles between 0° and 90° for the sample angle frame was developed to perform cone calorimeter tests at different sample angles. An advanced numerical predictive model based on the finite volume method was developed using the fire dynamics simulator (FDS) to quantify the dependency of ignition and combustion properties with sample angles. The numerical model was validated against experimental data from the cone calorimeter tests. The experimental and numerical analyses were conducted to quantify the effects of sample orientation on the different fire reaction properties i.e., ignition time, ignition temperature, burn time, heat release rate (HRR), critical heat flux, etc. The numerical method was utilised to analyse the mechanisms controlling the effect of heat convection and radiation blockage on the heating process. The study establishes that the sample orientation (with respect to the heat flux normal) has a significant influence on the fire reaction properties of natural fibre composites.
Highlights
Accepted: 2 August 2021Response of a material to an external heat flux and/or fire is quantified by the fire reaction properties
There were few assumptions made during the simulation, viz., combustible gases are immediately available and do not accumulate within the material; thermal equilibrium is established between gases and solid material; no change of incident heat flux during expansion of heated surface; reaction rate kinetics obtained from TGA can be used to simulate the fire reaction properties
At any given heat flux and sample angle, it is evident that the auto-ignition will be longer
Summary
Response of a material to an external heat flux and/or fire is quantified by the fire reaction properties. Conventional polymeric composites (reinforced by synthetic fibres) have been widely used in different engineering applications due to their superior mechanical properties. Dutta et al [25] recently conducted a comprehensive study on the effects of vertical and horizontal orientations of natural fibre reinforced composites (NFRc) on their fire reaction properties. They developed a detailed numerical model for predicting the fire reaction properties of NFRCs and validated against experimental data with good agreement. A complete spectrum of sample angles (from 0◦ to 90◦ ) with respect to the horizontal axis (X-axis, in Figure 1) was introduced to understand its effect on the ignition and combustion properties, in particular, for flax-polypropylene composites. The study aims at determining the influence of irradiance angle on the fire scenario, and whether the typical cone setups, namely the horizontal (0◦ ) and vertical (90◦ ) samples alone, can adequately characterise a fire situation
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