ENERGY-BASED APPROACH FOR CRACK INITIATION AND PROPAGATION IN VISCOELASTIC SOLID

The development of simple and computationally efficient analytical mod els for predicting the time-dependent initiation and propagation of cr acks in linear viscoelastic materials is of paramount importance in pr actical structural design using polymeric materials. A crack tip-model similar to that of Schapery is adapted (R. A. Schapery, A theory of c rack initiation and growth in viscoelastic media I. Theoretical develo pment. International Journal of Fracture, 1975, 11(1), 141-159), in wh ich the failure zone is assumed to be of highly-damaged material prece ding the physical crack tip. In the spirit of Wnuk's total energy rele ase formulation of elasto-plastic solid (M. P. Wnuk, Subcritical growt h of fracture (inelastic fatigue). Inter national Journal of Fracture Mechanics, 1971, 7(4), 383-407), the theoretical expression for the to tal energy release rate of viscoelastic materials has been derived thr ough the application of the correspondence principle. The derived theo ry has been applied to three specific case studies: (i) an infinite pl ate with central crack subjected to remote tension, (ii) an edge crack in a semiinfinite plate subjected to a pair of equal and opposite con centrated forces, and (iii) a pre-notched three-point bending beam. Th e significance of the influence of the plastic energy dissipation (due to viscoelasticity) on the crack initiation and propagation in these three cases has been examined and discussed in this paper. (C) 1997 El sevier Science Ltd.