Microscopic delamination processes and the resulting crack tip strain fields of graphite/epoxy composites

Thesis/Dissertation · Thu Dec 31 23:00:00 EST 1987

OSTI ID:5210837

Hibbs, M F

The microscopic failure mechanisms for five graphite/epoxy composites with different degrees of resin toughness were examined. Correlations between these failure mechanisms and the resulting delamination toughness were made for mode I, mode II and mixed mode loadings. A combination of scanning electron microscope (SEM) real-time fracture observations and post-failure fractography was used to identify the microscopic fracture mechanisms. The mode I, mode II, and mixed-mode energy-release rates were determined using unidirectional double-cantilever beam specimens. The mode I delamination energy release rate was calculated using linear beam theory, an area method, and a compliance calibration analysis. Results from these three different methods of analysis are compared and discussed. Two techniques for measuring the microscopic crack tip strain fields were developed and tested. These techniques used stereoimaging and direct measurement of the crack-tip displacements from SEM electron-beam-induced reference marks. Also, careful observations of the neat resin and composite fractured surfaces were made to evaluate the use of fracture morphology in failure analysis of composite materials.

• Research Organization: Texas A and M Univ., College Station, TX (USA)
• OSTI ID: 5210837
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
42 ENGINEERING
420500 -- Engineering-- Materials Testing
CARBON
COMPOSITE MATERIALS
ELEMENTAL MINERALS
ELEMENTS
EPOXIDES
FAILURES
FRACTURE PROPERTIES
GRAPHITE
MATERIALS
MATERIALS TESTING
MECHANICAL PROPERTIES
MINERALS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
TESTING