Accession Number:

ADA350573

Title:

Fracture Phenomena and Interface Properties of Composites: A Fundamental Approach

Descriptive Note:

Final rept. Sep 96-Dec 97

Corporate Author:

ILLINOIS UNIV AT CHICAGO DEPT OF CIVIL AND MATERIALS ENGINEERING

Personal Author(s):

Report Date:

1998-01-01

Pagination or Media Count:

42.0

Abstract:

This report presents a numerical approach to study the effects of bridging and shielding fibers on reduction in Stress Intensity Factor SIF at the crack tip. The variational foundation of the formulation is based on a modified Bu-Washizu variational principle. The crack is assumed to grow in a self-similar manner and an energy approach is undertaken to evaluate SIF at the crack tip. A perfect bond is assumed between the fiber and the matrix to account for the interaction of the two phases. It is observed that the area around the crack tip where the fibers strongly influence SIF extends to about three fibers ahead of the crack and five fibers in the wake of the crack. Numerical simulations also show that there is a certain limit beyond which increasing the ratio of the modulus of elasticity of the fibers w.r.t. the matrix may not help in reducing the SIF at the crack tip. A detailed study on the inter-phase stress fields around the reinforcing fibers shows that stronger fibers have a larger zone of influence and can potentially effect the stresses around the neighboring fibers. A study on temperature change indicates that thermal gradients result in a redistribution of the stress field and thus can have pronounced effect on the stress field at the crack tip.

Subject Categories:

  • Laminates and Composite Materials
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE