Crack formation during solid pyrolysis: evolution, pattern formation and statistical behaviour. (27th September 2019)

• Record Type: Journal Article
• Authors: Nguyen, Yen T.; Pence, Thomas J.; Wichman, Indrek S.
• Is Part Of: Proceedings. Volume 475:Number 2229(2019)
• Publication Date: 2019-09-27
• Subjects: crack morphology -- shrinkage stress -- crack growth -- thermal decomposition; Physical sciences -- Periodicals; Engineering -- Periodicals; Mathematics -- Periodicals; 500
• DOI: 10.1098/rspa.2019.0211
• Languages: English
• ISSNs: 1364-5021

Abstract

Abstract : 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.