Initiation crack propagation, impact resistance testing

Some of the more common mechanical properties are provided in Table 10.1 from IAEA (2009). Relative to various measures of toughness, some tests use a blunt notch, while others use a sharp crack to determine material resistance to crack initiation, crack propagation or both, and are conducted under either quasi-static (slow) loading or dynamic (fast) loading conditions. Of all these tests, the Charpy V-notch (CVN) impact test is the most commonly used. In addition to those mechanical properties, there are common reference fracture toughness indices used for RPV steels and many of those are also shown in IAEA (2009). These indices are important because they are used in various ways to normalize fracture toughness of RPV steels. 

A high level of uimotched impact resistance is seen in Fig. 18.12 both at room temperature and at — 18°C virtually independently from the fiber concentration. Unreinforced PP is soft enough to slide through the sample holder and not to break at all. Both crack initiation and propagation is tested in this experiment in contrast to the notched experiment in Fig. 18.13, where crack propagation plays the major role. Here, the impact resistance increases approximately linearly with the fiber content. 

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