Char cracking of medium density fibreboard due to thermal shock effect induced pyrolysis shrinkage

Li, Kaiyuan; Mousavi, Seyed Mahmoud; Hostikka, Simo

doi:10.1016/j.firesaf.2017.04.027

Cited by 22 publications

(21 citation statements)

References 30 publications

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“…This hypothesis is amply supported by empirical observation and more recently by specific experiments that have sought correlations between cracking depth, heat penetration depth and pyrolysis depth (e.g. [6]). This Introduction section is followed in §2 by a basic theoretical model for stresses induced by pyrolytic mass loss.…”

Section: Introductionmentioning

confidence: 88%

“…With respect to actual crack formation and growth, char shrinkage and fissure formation have been examined using principles of fracture mechanics and energy minimization. For example, Li et al [6] correlates total crack length over a heated surface to the shrinkage gradient of the material surface density, while Li et al [7] calculates the size of char blisters arising from the surface elastic strain. However, neither of these studies seek to account for the physical mechanisms that originate cracking by mass loss-induced stresses in the heated material.…”

Section: Introductionmentioning

confidence: 99%

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Crack formation during solid pyrolysis: evolution, pattern formation and statistical behaviour

2019

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As solids pyrolyse during combustion, they lose chemical and structural integrity by gradually degrading into residual char and forming defects such as voids, fissures and cracks. The material degradation process, which is coupled to the crack formation process, is described using a theoretical model and is numerically simulated using the finite-element method for a generic, charring, rubber-like material. In this model, a slab of material is subjected to an external, localized heat flux and, as the material degrades, cracks form when the local principal stress exceeds a defined cracking threshold. The magnitude of the cracking threshold σ c is systematically varied in order to examine its influences on crack initiation, evolution, distribution and behaviour over time. When σ c exceeds the maximum principal stress for the entire process, σ m , then no cracks are generated. We quantify how the average crack spacing, total crack length and crack initiation time depend upon the ratio σ c / σ m . Two characteristic domains of crack formation behaviour are identified from the crack initiation behaviour. Correlations are produced for the crack length evolution and final crack length values as functions of σ c / σ m . Crack intersection patterns and behaviour are described and characterized.

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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Crack formation during solid pyrolysis: evolution, pattern formation and statistical behaviour

2019

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“…Therefore, the microstructure and surface chemical structure differ from char formed by slow heating [226,227]. Rapid heating produces much more volatiles than slow heating [225], thus reducing relative solid yield, and also increases the number of char fissures [228] that can significantly alter the pyrolysis result in the transition zone, namely by providing pathways for flow of reactants [217]. However, higher temperatures result in char with higher fixed carbon content than chars prepared at lower temperatures [212].…”

Section: How Charring Affects the Wood Structurementioning

confidence: 99%

“…Char cracking is a typical thermal shock process induced by unbalanced shrinkage [228]. Zicherman and Williamson [217] suggested that cracks are initiated at 200-270 • C because of mechanical stresses caused by uncontrolled drying in the transition zone and simultaneous degradation of the highly stressed surface, as well as uneven cooling after exposure.…”

Section: Dimensional Stability Hygroscopicity and Absorption Of Surfa...mentioning

confidence: 99%

Review of Wood Modification and Wood Functionalization Technologies

Zelinka

Altgen

Emmerich

et al. 2022

Forests

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Wood modifications are becoming popular as a way to enhance the performance of wood, either to make it more durable, improve the performance of wood, or give it new functionality as a multifunctional or smart material. While wood modifications have been examined since the early 1900s, the topic has become a dominant area of study in wood science over the past decade. This review summarizes recent advances and provides future perspective on a selection of wood modifications, i.e., the methods that are currently commercialized (acetylation, furfurylation, and thermal modification), a rediscovered ancient practice (charring), a family of polymerization modifications that have so far made it to the pilot scale, and examples of novel wood-based functional materials explored at laboratory scale.

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“…14,71,73 Shen et al 196 derived formulas for cracking of wood from an experimental study which can be readily implemented into pyrolysis model. Li et al 197 studied the char cracking of MDF and used FDS to model pyrolysis and modeled the mechanical process separately. Some charring materials such as PU foam undergo smoldering combustion which further complicates the modeling process because the chemical kinetics needs to be explicitly described.…”

Section: Applicationsmentioning

confidence: 99%

Pyrolysis modeling, sensitivity analysis, and optimization techniques for combustible materials: A review

Nyazika

Jimenez

Samyn

et al. 2019

Journal of Fire Sciences

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Over the past years, pyrolysis models have moved from thermal models to comprehensive models with great flexibility including multi-step decomposition reactions. However, the downside is the need for a complete set of input data such as the material properties and the parameters related to the decomposition kinetics. Some of the parameters are not directly measurable or are difficult to determine and they carry a certain degree of uncertainty at high temperatures especially for materials that can melt, shrink, or swell. One can obtain input parameters by searching through the literature; however, certain materials may have the same nomenclature but the material properties may vary depending on the manufacturer, thereby inducing uncertainties in the model. Modelers have resorted to the use of optimization techniques such as gradient-based and direct search methods to estimate input parameters from experimental bench-scale data. As an integral part of the model, a sensitivity study allows to identify the role of each input parameter on the outputs. This work presents an overview of pyrolysis modeling, sensitivity analysis, and optimization techniques used to predict the fire behavior of combustible solids when exposed to an external heat flux.

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Char cracking of medium density fibreboard due to thermal shock effect induced pyrolysis shrinkage

Cited by 22 publications

References 30 publications

Crack formation during solid pyrolysis: evolution, pattern formation and statistical behaviour

Crack formation during solid pyrolysis: evolution, pattern formation and statistical behaviour

Review of Wood Modification and Wood Functionalization Technologies

Pyrolysis modeling, sensitivity analysis, and optimization techniques for combustible materials: A review

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