This thesis is written in the interest of fracture mechanics. The breakage of machine components under normal loading is frequently diagnosed as fatigue. However, such diagnoses are in need of further clarification. Basically, it is assumed that flaws in the material tend to expand under the influence of tensile stresses. These flaws may be present as a result of processing, or develop from environmental attack. They serve to concentrate stresses, which are the dominant factor in their growth. Various materials tend to resist the growth of flaws more than do other materials. A testing procedure has been developed that renders understanding on a macroscopic scale of the growth of anomalies in materials under stress. It is the intention of this thesis to relate the theory of fracture. Permission was granted to employ a tear resistance evaluation as thesis material, after half of the specimens had been consumed in testing. The investigation was subsequently expanded to determine additional fracture toughness information. Results from additional investigations are included to illustrate other facets in fracture mechanics.