Interface bond strength

Fig. 3.8. Plots of interface bond strength, Tt, versus embedded fiber length, L. (a) for a carbon fiber-epoxy matrix system and (b) for a Hercules IM6 carbon fiber-acrylic matrix system. After Pilkethly and Doble (1990) and Desarmont and Favre (1991).

Apart from the elastic stress transfer at the perfectly bonded interface, another important phenomenon that must be taken into account is the stress transfer by friction, which is governed by the Coulomb friction law after the interface bond fails. Furthermore, matrix yielding often takes place at the interface region in preference to interfacial debonding if the matrix shear yield strength, Xm is significantly smaller than the apparent interface bond strength, tb. It follows thus... 

Etchant Exposure time (h) Interface bond strength (MPa)... 

TiOi) result in substantial improvement in strength and toughness of the composites. The BN coating reduces the interface bond strength between the SiC reaction layer ind the mtitrix. A duplex coating of SiC/BN applied to the Nicalon... 

Some deformation leading to toughness may intuitively be described. Matrix deformation, for example, is expected to be larger for either low interface bonding strength or low elastic modulus of filler particle because the constraint in the vicinity of the crack tip caused by either of those properties on matrix is weak. Deformation of filler particles in relation with various conditions and relative quantities, however, is no longer intuitive. In this section, further analysis using Mohr circles is conducted for ME and MEH. 

Indirect methods to measure the interface bond strength include the interlaminar shear strength test and the transverse strength test. A properly designed flex test with fibers parallel to the beam s longitudinal axis is another sensitive... 

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