Zhandarov, S. ; Pisanova, E. ; Mäder, E.

A direct observation of crack propagation in the microbond test was carried out for five different fiber/polymer matrix systems. This technique appeared to be a very effective tool for interface characterization. Experimental plots of the force required for further crack propagation as a function of debond length were analyzed using both energy-based and stress-based models of debonding. The fracture mechanics analysis was used to construct families of crack resistance or

the interfacial parameters with good accuracy.

Journal of Adhesion Science and Technology

679-704

http://dx.doi.org/10.1163/1568561054890462

December 2005

**Is there any contradiction between the stress and energy failure criteria in micromechanical tests? Pt. III. Experimental observation of crack propagation in the microbond test**A direct observation of crack propagation in the microbond test was carried out for five different fiber/polymer matrix systems. This technique appeared to be a very effective tool for interface characterization. Experimental plots of the force required for further crack propagation as a function of debond length were analyzed using both energy-based and stress-based models of debonding. The fracture mechanics analysis was used to construct families of crack resistance or

*R*-curves which showed the variation of energy release rate,*G*, with the debond length, and included the effect of interfacial friction in debonded regions. For the first time, analogs of the*R*-curves were created within the scope of the stress-based model to present the local shear stress near the crack tip, , as a function of crack length. In both models, the behavior of the interfacial parameter (*G*or ) strongly depends on the assumed value of the interfacial frictional stress (_{f}). However, for each matrix/fiber system there exists such a_{f}value for which the investigated parameter is nearly constant over the whole region of stable crack propagation (70–90% of the embedded length). Moreover, these best-fit_{f}values for each specimen appeared to be practically the same for both energy-based and stress-based approaches. Thus, both interfacial toughness,*G*_{ic}, and local interfacial shear strength,_{d}, adequately characterize the strength of a fiber/matrix interface. Extrapolation of*R*-curves and their analogs to zero crack length allows measurement ofthe interfacial parameters with good accuracy.

**Quelle**Journal of Adhesion Science and Technology

**19****Seiten**679-704

**DOI**http://dx.doi.org/10.1163/1568561054890462

**Erschienen am**December 2005