Findings made through the indentation testing of composites are presented in this thesis.
The concept was developed as an attempt to evaluate the interfacial shear strength at a mesolevel,
possibly overcoming the deficiencies of present techniques. Vickers Microhardness Testing
and Continuous Ball Indentation Testing (CBIT) of composite materials provided data for assessing
the sensitivity of indentation techniques to interfacial characteristics and engineering properties.
Both methods proved capable of discerning the level of fiber-matrix adhesion. The CBIT presented
the greatest potential for making quantitative measures of interfacial shear strength. A unique
micromechanics model of the contact situation predicted failure events and trends consistent with
the observed data from the CBIT. The present elastic model predicted an interfacial shear strength
slightly higher than those reported in the literature. However, the interface strength obtained
through the CBIT provides more of an engineering assessment of the interfacial quality when
compared to other techniques.
Both experimental and analytical results suggest that indentation testing of composites is
most sensitive to shearing characteristics of the system. Vickers and ball penetration results
displayed some correlation to global laminate properties. Vickers hardness shows a close
relationship to IITRI compression strength only when fiber compressive failure is observed in·the
laminate test. The CBIT provides the best opportunity for exploring fiber composite stress-strain
information.
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