A numerical study of crack-tip plasticity in glassy polymers

Abstract

A numerical study of crack-tip plasticity in glassy polymers Lai, J.; van der Giessen, E. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractThis paper reports on a finite element analysis of the crack-tip plastic zone and near-tip fields in viscoplastic glassy amorphous polymers. The constitutive model employed in this study accounts for the typical shear yielding behavior of glassy polymers, i.e., the intrinsic softening upon yielding and the subsequent orientational strain hardening. The small scale yielding, boundary layer approach is adopted to model the local finite-strain deformation processes in front of a crack with a blunt notch, Numerical[ results show that the shape of the plastic zone near the tip of a Mode I crack in a glassy polymer depends sensitively on the combined effect of softening and strain hardening. Softening tends to intensify the plastic deformation, while the subsequent hardening tends to depress plastic flow and gives rise to continuous propagation of the current plastic zone. "lhus, the plastic zone in typical amorphous polymers is found to be quite different from the HRR solution for yielding in hardening metals. It is also found that the distribution of hydrostatic stress, which is probably responsible for crazing, is intimately related to the pattern of the plastic deformation in front of the crack tip.

Modeling of the competition between shear yielding and crazing in glassy polymers

“…A significant advance was made by the model for plastic deformation in glassy polymers developed by Boyce et al (1988). Lai and Van der Giessen (1997) recently adopted this model for an analysis of the development of plasticity around a blunted mode I crack in glassy polymers. This study pointed out that, owing to the intrinsic softening and final orientational hardening, plasticity develops in a pattern of shear bands, distinctly different from the standard fields in strain hardening metals.…”

A possible mechanism for cross-tie fibril generation in crazing of amorphous polymers

“…The initiation of crazing is primarily controlled by the hydrostatic stress, whereas shear yielding is a result of large shear stresses. Shear yielding alone does not lead to fracture immediately but intersecting shear bands may assist in triggering crazing by locally enhancing the hydrostatic stress [1,2].…”

Effects of microstructure on crack tip fields and fracture toughness in PC/ABS polymer blends

“…As already mentioned earlier, plastic deformation at a notch under plane strain conditions in neat PC takes place by the formation of a pair of shear bands which intersect at some distance ahead of the notch (Narisawa and Yee 1993;Lai and Van der Giessen 1997;Estevez et al 2000;Gearing and Anand 2004). Close to this intersection a concentration of hydrostatic stress appears (Fig.…”

“…The computational models in the present work are two-dimensional and plane strain conditions are considered. Mode I loading is imposed in terms of the respective displacements u prescribed as far-field boundary conditions, see e.g., (Lai and Van der Giessen 1997). Inside the process zone the two-phase blend microstructure is explicitly resolved and different morphologies-particulate or lamellar-are considered as sketched in Fig.…”