Linear elasticity, stress-concentration studies

Linear elastic fracture mechanics studies on toughened brittle plastics at room temperature concentrated on thermosetting resins, which have sufficiently high yield stresses to meet the requirements of Eq. 12.7. There has been increasing emphasis on ductile fracture mechanics in testing the toughened thermoplastics. An alternative approach is to determine the parameter, Jj, which is the quantity corresponding to Gj in linear elastic fracture mechanics, as discussed below. 

The index of sensitivity, cp, to stress concentrations, which is equal to the ratio of the Kic values, obtained by the SEVNB and SENB methods is shown in Table 2.3. In the tests of elastic materials,

deformation behavior of V-notched ceramic specimens with a cp value of about 0.6 produced linear load-deflection diagrams or diagrams with small nonlinearity, as seen in Fig. 2.11 of lines 1 and 3, which are the results of comparatively slow crack growth. 

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