Fibre Debonding

The performance of many fibre composite materials is very sensitive to the mechanical properties of the interface region. This is often important for metal matrix composites, where considerable uncertainty surrounds the question of how best to tailor the interfacial behaviour in order to optimise selected mechanical properties. Part of the problem has lain in incomplete specification of the interfacial response.

Various tests have been devised, but for most, specimens must be produced in a special operation which differs from the normal composite manufacturing route and may thus create different interfacial microstructures and residual stresses. One of the few tests which can be applied to normal fibrous composite material is the single fibre push-out test. This has received considerable attention recently, both experimentally and theoretically. Since the load may rise or fall during fibre debonding, depending on debonding and frictional sliding stresses, a continuous load/displacement record is desirable; such a record is the principal output of the NanoTest high load head (MicroTest).

In the NanoTest high load head (MicroTest), the ability to perform push-out tests of the type reported in the technical literature is supplemented by the simultaneous imposition of in-plane biaxial tension. This allows a radial tensile stress to be imposed on the fibre-matrix interface, which allows additional information to be obtained on debonding and/or frictional sliding of the fibre.