Accession Number:

ADA244600

Title:

Determination of Interfacial Properties

Descriptive Note:

Final rept. 20 Feb 1989-19 Aug 1991,

Corporate Author:

ROCKWELL INTERNATIONAL ANAHEIM CA SCIENCE CENTER

Report Date:

1991-11-01

Pagination or Media Count:

41.0

Abstract:

The primary objective of this program was to determine surface displacements in the resin matrix adjacent to a graphite fiber during applied fiber strain. These data are to be used to quantify the effect of interphases on fiber-matrix interfacial elastic properties. We successfully demonstrated the measurement of in-and out-of-plane displacement fields with sufficient spatial resolution to produce data for calculating the modulus and thickness of interphase layers in the epoxy within a few microns of the graphite fiber. The interphase layer was modified by using different surface treatments and coatings applied to the AS-4 fibers. The shear lag and finite element models used by NADC and ourselves to model the interphase are elastic. Our initial efforts at measuring surface displacement indicated that significant inelastic effects occurred during first load. At fiber strains above 0.4, the inelastic effect could be shaken-out or relaxed by cyclic loads, after which the measured displacements were elastic and showed significant influence of the fiber surface treatment. However, substantial changes in the matrix could have occurred during the relaxation process, including microcracking of the interface. Measurement of the small displacements induced by the low fiber strains of less than 0.1 required the improved sensitivity obtained by a unique approach to recording SEM images of surface displacements resulting from load changes during image recording.

Subject Categories:

  • Laminates and Composite Materials
  • Plastics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE