Investigating Near-Tip Damage and Crack Growth Behavior in a Solid Propellant
Abstract
When cracks occur, whether resulting from the manufacturing process or from service loads, the stresses near the crack tip will be redistributed according to nonlinear material behavior. Depending on the magnitude of the local stresses and the local strength, various defects, microvoids or microcracks, can develop in the crack tip region. And, depending on the severity of these defects, crack growth behavior can be significantly affected. Therefore, to obtain a fundamental understanding of crack growth behavior in particulate composite materials, the effect of the defect on local fracture behavior near the crack tip needs to be determined. In recent years, a considerable amount of work has been done studying crack growth behavior in particulate composite materials. This work was based on linear fracture mechanics. The principles of classical fracture mechanics are well established for single-phase materials. However, experimental evidence indicates that linear fracture mechanics theories have been applied to particulate composite materials with varying degrees of success. In this study, pre-cracked specimens were used to study local damage near the crack tip in a solid propellant under a constant strain rate at room temperature, using biaxial strip specimens. The effect of local damage on crack growth rate also was investigated. The results indicate that, on a macroscale, the material can be considered a continuum, and plane strain fracture toughness may not exist for it. In the highly strained region at the crack tip, material may be damaged and voids may develop and the crack can grow by the coalescence of the voids with the crack tip. The crack-damage interaction is a contributing factor to the fluctuation of the crack growth behavior. Experimental results also indicate that crack tip blunting occurs during the loading process, and that crack growth consists of a blunt-growth-blunt phenomenon that appears to be highly nonlinear. (6 figures, 8 refs.)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 2001
- Accession Number
- ADA410276
Entities
People
- Chun Ting Liu
Organizations
- Air Force Research Laboratory