Characterization and control of the fiber-matrix interface in ceramic ...

7. CHARACTERIZATION OF THE FIBER-MATRIX INTERFACE
Quantitative analysis of the interfacial bond strength and
frictional stresses and detailed characterization of the chemical
interactions at the fiber-matrix boundary are essential to begin relating
composite properties to interfaces.
When the nature of the fiber-matrix
interface is fully understood, interfacial pretreatments can be employed
to control fiber-matrix bonding and interaction and, ultimately, the
mechanical behavior of composite materials.
7.1 Quantitative Analvsis of Forces at the Interface
Numerous methods have been developed to quantify the strength of
interfacial bonding in fiber-reinforced composites (83-88).
These have
hvolved either pushing or pulling on individual fibers embedded in a
continuous matrix and determining the required forces.
Such tests permit
a quantitative determination of the bond strength arid interfacial
frictio;lal stresses, which are derived from relatively shpl~ load and
displacement relationships.
7.1.1 Indentation techniques
Several indentation methods for measuring interfacial bonding forces
have been examined (85-88).
These techniques involve using a micro-
hardness indentor to apply a force to the end of a fiber embedded in a
matrix.
The bond strength can be calculated from the applied load and
the displacement of the fiber.
In the method developed by Marshall (88), a load is applied to the
end of a single fiber embedded in a matrix and having an orientation
perpendicular to a prepared surface (Figure 7.1).
An analysis of the
forces needed to displace a fiber in a thin specimen yields
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