Micromechanical analysis of the fiber push-out and re-push test

The objective of this work is to employ the variational model of a concentr ic cylinder to model accurately the fiber push-out (and re-push) test used for evaluation of interfacial properties. In this paper, the detailed stres s distributions and load/displacement solutions obtained by considering a v ariety of interface boundary conditions (such as adhesively bonded friction ally sliding and debonded) are compared with a numerical elasticity solutio n which uses the material properties of a polyester/epoxy system for which experimental data are also available. The present approach is shown accurat ely to predict the force versus debond length relationships in the progress ive debonding portion of the push-out test while demonstrating a boundary l ayer effect in the behavior of fiber axial stress near the free surface and interfacial radial and shear stress in the slip region. The apparent debon d toughness has been defined by using energy-balance arguments during a cri tical finite crack extension. The increase in crack-tip driving force with the length of the debond is attributed to crack-tip mode mixity while the m agnitude of the release rate of shear energy is observed to be nearly const ant. By using the critical shear-energy release rate criterion, the load/di splacement response is then predicted during push-out and re-push tests. Fi nally an estimate of the maximum debond stress, externally applied displace ment and the critical debond length are made at the point of instability. A ll of these estimates are in good agreement with the experimental measureme nts. Published by Elsevier Science Ltd.