Parameters, debond length

Figure 4. Debond length vs. debond toughness/matrix toughness ratio a) for several values of the composite parameter k and the particle volume fraction / 0.15, b) for several values of the particle...

Then, as Fig. 5 shows, the transition from debonding to no-debonding regime taies place for a set of combination of values of the parameter k and the particle volume fraction /. Each of these combinations relates to a particular value of the debond length see Fig. 6. Choosing/as the independent variable, the toughening ratio iu Eq. (30) can be plotted vs./for various values of see Fig. 8. It is... 

From the discussion presented above, it is clear that the stability of the debond process can be evaluated by a single parameter, Zmax, which is the shortest (remaining) bond length needed to maintain the debond process stable, and is a constant for a given composite system. Therefore, three different interface debond processes are identified in the following totally unstable, partially stable and totally stable debond processes. The schematic plots of the applied stress versus displacement curves are illustrated in Fig. 4.25 for these debond processes. 

If the fibres are shorter than / , failure of the composite occurs after the debond regions have extended along the fuU length of the fibre. The entire fibre is then merefy slipping within its hole in the matrix it cannot be raised to its failure stress and so cannot be broken. When failure of the matrix finalty occurs, the fibre simpfy slides out of the matrix, leaving behind an empty hole. In practice, then, is a parameter of vital importance. Strenuous efforts are usually made to ensure that l>lf (6.N.8). 

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