A simplified model on vertical density profile and shrinkage ratio of virgin and charred medium density fibreboard

Abstract

This work is part of a wider scope of research on developing comprehensive pyrolysis model for medium density fibreboard (MDF) in fires. A simplified model is developed to predict the vertical density profile of virgin MDF. The model shows that vertical density profile can be reproduced using a second order conic curve. Several sets of experimental data are used to validate the model with promising results that are presented. Further investigation shows that the density difference between surface and core densities tends to maintain constant within a range of 300 to 450 kg/m3. Moreover, the model can predict the mean density with an error less than 30 kg/m3. Typical MDF panels were experimentally charred using thermogravimetric analysis and cone calorimetry to investigate the shrinkage and density of char. The actual char density is measured as 330 kg/m3 with a uniform density distribution along the char layer thickness. A model is developed to predict the shrinkage ratios. The restraining effect caused by surface deformation will lead to different vertical and horizontal shrinkage ratios. The volume reductions at vertical and horizontal directions are experimentally measured as 40% and 20% for the two tested MDF panels, which is comparable with the model predictions. Copyright © 2013 John Wiley & Sons, Ltd.

A thermomechanical explanation for the topology of crack patterns observed on the surface of charred wood and particle fibreboard

“…In the following, w tt ≡ ∂ 2 w/∂t 2 and so on. 3 The following argumentation is based on thin plate theory, which is extensively discussed in [36].…”

“…During combustion, the char acts as a heat barrier between the combustion zone and virgin material, reducing the burning rate of the uncharred material [1]. The shrinkage and cracking of the char layer have been found to influence the pyrolysis [2,3] and the fire resistance of structures made of cellulosic materials. For instance, the char layer reduces the heat transfer to the virgin material while the cracks enhance it due to the flame attachment to the crack locations [4].…”

“…In the studies of wood pyrolysis, i.e. the thermal decomposition of solid into flammable liquids and gases and solid char, attention has mainly focused on physicochemical processes taking place during and beyond pyrolysis, ignoring the thermomechanical processes occurring below the pyrolysis temperature T p ≈ 300 • C [3,4,9,10,11]. Understanding the mechanisms of char cracking can thus lead to improved accuracy of the combustion modelling of wooden materials, enabling more profound considerations of charring behaviours in fire safety and energy technologies.…”

Modelling pyrolysis of charring materials: determining flame heat flux using bench-scale experiments of medium density fibreboard (MDF)

“…Therefore this article specifically presents the burning behaviours of MDF in bench-scale combustion experiments while the thermophysical and kinetics properties were presented elsewhere in the literature (Li et al, 2013a(Li et al, , 2013b(Li et al, , 2014. These experimental data will be used to validate a developed pyrolysis model while the measured irradiances will be used as the boundary conditions in modelling.…”

Experimental study on fire properties of interior materials used in low‐floor light‐rail trains

“…Effects of external heat flux and sample thickness on combustion characteristics of EPDM and GC were investigated. Thermogravimetric analysis and cone calorimetry were employed by Li et al to investigate the shrinkage and density of char from fiberboard in fires. A literature review was performed by Lattimer and McKinnon to assess the state of knowledge of effects of railcar interior finish materials on fire growth and fully developed fires from railcars.…”