Fatigue
Thermoformed parts exposed to cyclic loading often fail at substantially lower stress or stain levels than parts under static loading. This phenomenon is known as fatigue. Applications that expose parts to heavy vibration or repeated deflections - such as a high-use snap latch closure or truck parts - need plastics with good fatigue characteristics.
Fatigue properties are sensitive to many factors, including notch effect, environmental frequency and temperature. The type and severity of fatigue loading determine which material fatigue data applies. A reduced single point allowable strain limit may suffice in a simple snap-latch arm subjected to few deflections over the product life.
Calculations for parts produced with Bayblend ET 1000 PC/ABS that are subjected to many deflections at room temperature and 7Hz frequency will use the data presented in the chart below (click on chart for larger image).
