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

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fiber-matrix bonding; thus, a fundamental understanding of the fibermatrix
interface is necessary to design and produce composites that
possess the optimum combination of strength and fracture resistance.
The study of interfaces is not limited to the mechanical aspects,
but is interdisciplinary, a combination of materials evaluation and
mechanical relationships.
A practical correlation relating interfaces to
composite properties is impossible without an understanding of the
mechanical, physical, and chemical interactions that are present in a
given system.
Chemical, physical, and mechanical bonding are present at
the interfaces in all composite systems.
These factors combined with the
mechanical properties of the individual components can be used to explain
the observed behavior of A rnulticomponcnt composite material.
6.2 Role of tk!e Interface
The mechanical properties of filamentary composites are influenced
strongly by the fiber-matrix interface.
The interfacial bond affects
matrix-cracking and composite-fracture behavior (57,78-80).
For
composites having a very strong interfacial bond, a crack propagating in
the matrix will pass undisturbed through the fibers and the composite
will fail in a brittle manner, much the same as the unreinforced matrix
material does (Figure 6.1).
For composi.tes having poorly bonded
interfaces, the fracture process begins progressively with debonding at:
the fiber-matrix interface, followed by subsequent matrix failure, fiber
slip and pull-out, and finally, fiber failure (81,82). These energyabsorbing
mechanisms all contribute to improve fracture toughness and are
controlled by the strength of the fiber-matrix bond.