Functional Fatigue of Shape Memory Polymers

In the present study the functional fatigue in the commercial SMP Veriflex® which is associated with repeating up to 20 programming/1‐WE cycles has been examined. The material is characterized by a glass temperature Tg of 67 °C, above which it looses all its strength. During tensile testing at 21 °C (T Tg) the material can be strained up to 225 % before rupture occurs while stresses slowly increase to values as low as 0.4 MPa. Thermomechanical cycles including programming, cooling and unloading and heating to trigger the one way effect result in an increase of irreversible strain associated with a corresponding decrease of recovery ratio at the beginning of thermomechanical cycling. In parallel a wavy surface structure evolves during cycling. In the present study the functional fatigue in the commercial SMP Veriflex® which is associated with repeating up to 20 programming/1‐WE cycles has been examined. The material is characterized by a glass temperature Tg of 67 °C, above which it looses all its strength. Thermomechanical cycles including programming, cooling and unloading and heating to trigger the one way effect result in an increase of irreversible strain associated with a corresponding decrease of recovery ratio at the beginning of thermomechanical cycling. In parallel a wavy surface structure evolves during cycling.