Stress Intensity Factors - Illustrative Examples

To illustrate the use of the Westergaard stress function approach, the case of a central crack of length 2a in an infinitely large thin plate (i.e., for generalized plane 

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Another method used to improve the fracture energy of BMI resins consists in mixing the thermosetting material with linear thermoplastic polymers. This can be illustrated by the behaviour of mixtures containing Compimide 796 and TM 123 BMI resins with GE Ultem 1000 , poly(ether-imide) 26 (Fig. 13) [70]. The critical stress intensity factor Kic of the linear polymer is six times higher than that of the BMI matrix and does follow the mixture law for aU BMI/Ultem combinations. The linear polyimide can also be added as 20- 0 [im spherical particles to the BMI resin before it is polymerised. In another example, particles of a soluble... 

The discussion thus far has emphasized sensitivity of the frequency of C02 s v3 mode to local stress, sensitivity of its absorption intensity to IR polarization, and sensitivity of both properties to resonant coupling of dimers. For the type of crystals under consideration, which consist mostly of simple hydrocarbon groups, these factors probably dominate in determining the IR spectral characteristics. Other factors can be involved, however, and although they can make simple interpretation of the spectra more problematic, they can also provide additional information about the environment of the C02 probe molecule. The following examples illustrate how one can track the motion of C02 over distances of 1-15 A by observing its proximity to free radical centers or to halogen or deuterium substituents in the crystal lattice. This information complements the previously discussed structural studies, which related to structure within the dimer rather than to the location of the C02 in the crystal matrix. 

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