Fracture energy strength, comparison

Figure 8.27 Comparison of fracture energy, strength, fracture strain, and lightweight nature of various porous and dense silicon nitrides. PSN A and >6 are porous materials fabricated through tape

We have determined that S/I/S triblock copolymers may be prepared to show anisotropic behavior with respect to fracture in adhesively bonded lap shear joints made with rigid substrates. Table 2 summarizes joint strength and fracture energy data for lap shear joints prepared with the orientation (machine) direction of the adhesive layer either parallel or perpendicular to the fracture axis of the joint. The important comparison is that of the fracture energies of the different orientations for the 50% styrene S/I/S copolymer (E2) sample. The high fracture energy for the parallel orientation corresponded exclusively to ductile drawing failure, the perpendicular orientation... 

The ratio, a, of the fracture energy to the sample cross-section B D is termed impact strength (Schlagzahigkeit). Such a notation creates the allusion that an is a fracture surface specific material property. It has frequently been pointed out that this is not the case [88-89]. Neither Wg nor W in are proportional to the sample cross-section. A comparison of an values should only be made, therefore, if all values are obtained from one type of test, preferably even from specimens of identical geometry. Impact strength values an of Charpy un-notched specimens (DIN 53453) at 20 °C range from 3.5—12 kJ/m for filled phenol melamine and urea resins,... 

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