Fundamental Studies in Crack Initiation.
Abstract
Damage evolution before crack initiation in an amorphous polymer show that damage consists of a core of highly dense crazing and peripheral less dense zone of crazing. Analysis of the kinematics of damage at different times involves comparisons of the inertia moments of damage distributions. The results indicate that damage evolution can be approximated by a linear transformation of the space variables. The crack initiates within a core zone immediately ahead of the notch. The experimental results suggest that damage density within the core is independent of the loading conditions considered herein. An energy release rate is evaluated with the use of a semi-empirical method. Correlation of the elementary movements of the damage zone with the energy release rate shows that damage growth decreases monotonically. Assuming that damage evolution is a stress-temperature driven process, it is shown that a first order reaction equation describes reasonably well damage growth within the core zone. An activation energy for defect nucleation is found twice the enthalpy of activation for secondary chain motions below glass transition. This result indicates that chain motions and chain scission are possible process leading to crack initiation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1996
- Accession Number
- ADA311401
Entities
People
- John Botsis
Organizations
- University of Illinois at Chicago