Quantitative approaches to particle cavitation, shear yielding, and crazing in rubber-toughened polymers

• Published in: Journal of polymer science. Part B, Polymer physics Polymer physics, 2007-06, Vol.45 (12), p.1399-1409
• Main Author: Bucknall, C. B.
• Format: Article
• Language: English
• Subjects: Applied sciences; blends; crazing; Exact sciences and technology; Mechanical properties; modeling; Organic polymers; Physicochemistry of polymers; Properties and characterization; theory; toughness; yielding
• ISSN: 0887-6266; 1099-0488
• DOI: 10.1002/polb.21171

Models for rubber particle cavitation, shear yielding, and crazing are reviewed, and their ability to predict the large‐strain deformation behavior of toughened polymers is discussed. An existing model for void initiation and expansion in rubber particles correctly predicts the observed trends: cavitation resistance increases when either the shear modulus or the surface energy of the rubber is increased, or the particle size is reduced. However, further work is needed to improve quantitative modeling of the thermally‐ and stress‐activated void nucleation step. Shear yielding, which is also a rate process, is much better understood; here, the main problems in modeling relate to the formation and evolution of porous shear bands. Craze growth and failure are also reasonably well understood, but previous attempts at modeling have been hampered by uncertainties about craze initiation. To overcome these difficulties, a new theory of crazing is proposed, which treats initiation as a fracture process, and defines a new materials property, Gnasc, the energy required to form unit area of nascent craze. Because nascent crazes are ∼20 nm thick, Gnasc is low: calculations give values