Interface cracking energy

Fig. 6.20. Ra(io of the strain energy release rates, Gl/Gt, plotted as a function of the material parameter, ot, for a doubly deflected interface crack. After Gupta et al. (1993).

Another way of increasing film adhesion is to adjust the interface adhesion energy so that it is comparable with the fracture energy of the polymer coating. Under such conditions, the interface crack prefers to deflect into the bulk of the coating material, as illustrated in Fig. 14.24(a). Once this happens, the interface crack has to be started again and this requires much extra force. It is rather like... 

More direct measures of interface debonding energy are provided by the pull-out or push-out tests shown in Fig. 16.26. When a tensile force is applied to a fiber to extract it from its composite matrix, an interface crack eventually starts to run along the fiber. It is obvious from a simple fracture mechanics argument that the stress on the fiber to propagate the crack, assuming a very compliant matrix, must be given by an expression of the form... 

Fig. 4.18. Experimentally determined interface fracture energy F as a function of the local stress state phase angle for the epoxy—glass bilayer system. The measurements were made using an edge-cracked bimaterial strip specimen on which prescribed values of normal and shear displacements were imposed. The different symbols represent four different sets of experiments conducted for this material system. Adapted from Liechti and Ghai (1992).

Fig. 4.48. The plane spanned by two nondimensional combinations of system parameters, with (

---