CREEP AND FATIGUE ENDURANCE GUIDELINES

HERE ARE SOME GUIDELINES TO FOLLOW:

RULES ABOUT CREEP -

1. Increasing the load on a molded part increases the creep rate.
   
   
2. Increasing the level of reinforcement in a composite increases its resistance to creep.
   
   
3. Particulate fillers provide better creep resistance than unfilled resins but are less effective than fiber reinforcements.
   
   
4. Glass fiber reinforced amorphous resins generally have greater creep resistance than glass fiber crystalline resins containing the same amount of glass.
   
   
5. Carbon fiber reinforcement is more effective in resisting creep than glass fiber reinforcement.
   
   
6. Flame retardant additives affect different resins in different ways; each case should be evaluated separately.
   
   
7. The effect of a flame retardant additive on flexural modulus provides an indication of its effect on long term creep.

RULES ABOUT FATIGUE ENDURANCE -

1. Fiber reinforcements provide significant improvement in fatigue life of a resin; carbon fibers improve this property more than glass fibers do.
   
   
2. Effects of moisture in a service environment on fatigue endurance should be considered when hygroscopic materials such as nylon are used.
   
   
3. For service involving a large number of fatigue cycles, crystalline resins offer more predictable results than amorphous resins because crystalline materials usually have a definite fatigue endurance limit.
   
   
4. For optimum fatigue life in service involving both high stress and fatigue loading, reinforced high temperature resins are recommended.