Crack propagation plastics mechanical behavior

In fundamental solid mechanics including fracture mechanics studies, the requirement is to determine the stress-strain curves and to study the propagation of a crack in a substance. Understanding the behavior of crack propagation was essential for the modem day development of plastic products. 

Last is that the mechanism of compact failure also depends on strain rate. Figure 21-118 illustrates schematically the crack behavior observed in compacts as a function of capillary number. At low Ca, compacts fail by brittle fracture with macroscopic crack propagation, whereas at high Ca, compacts fail by plastic flow, which is more desirable to promote growth. 

From studies of service behavior and from extensive laboratory investigations, the well-established terms stress-corrosion cracking (SCC) and corrosion fatigue have been shown to relate to a continuum of failure modes classified as environment-sensitive fracture. In many environments, the addition of stress, with associated strains, introduces a variable that can result in brittle failure in the sense of very limited plastic flow in otherwise ductile materials such as the stainless steels. Environment-sensitive fractures propagate at an advancing crack tip at which, simultaneously, the local stresses can influence the corrosion processes, and the corrosion can influence the crack-opening processes. Since these processes proceed by kinetic mechanisms, they are time and stress dependent with the result that the crack propagation rate can become very sensitive to the stress application rates. Conventional SCC usually has been associated with static stress, but this is seldom realized... 

Hidemitsu Hojo et al. (Hidemitsu et al., 1998) reviewed the behavior, the forms and mechanisms of corrosion of resins and glass fiber reinforced plastics under several aqueous solutions. They concluded that the concept of the corrosion rate of metals could be applied even in plastics and fiber reinforced plastics for each corrosion form. The corrosion resistance of the composites is mainly dependant on the resin s corrosion resistance properties and the corrosion crack propagation. Applications requiring corrosion resistant composite materials usually use epoxy and polyester resin as the composite matrix because these thermosets have high resistance to chemical attack. Among the various type of resins epoxies dominate the... 

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