Short-Duration Rapid and Impact Loads

This chapter has thus far dealt with the behavior of plastics and composites during short-and long-term loading conditions. As with any material, the properties obtained under 

Data on long-fiber glass-reinforced grades are for Verton compounds. To convert psi to pascals (Pa), multiply by 6.895 x 10.  

Designers with a background in using other materials will recognize both the similarities and the differences in the behavior of the plastics discussed. 

Deformation is an important attribute in most plastics, so much so that it is the very factor that has led them to be called plastic. For designs requiring such traits as toughness or elasticity this characteristic has its advantages, but for other designs it is a disadvantage. 

However, there are plastics, in particular the RPs, that have relatively no deformation or elasticity and yet are extremely tough (see Fig. 3-73). This type of behavior characterizes the many different plastics available (see Table 3-10). Some, tough at room temperature, are brittle at low temperatures. Others are tough and flexible at temperatures far below freezing but become soft and limp at moderately high temperatures. Still others are hard and rigid at normal temperatures but may be made flexible by copolymerization or adding plasticizers. 

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