Abstract
In the present study, the functional fatigue in the commercial SMP Veriflex®, which is associated with repeating up to maximum 40 programming/one-way effect (1WE) cycles, has been examined. The material is characterized by a glass transition temperature (T g) of 67°C, above which it looses all its strength. An interesting comparative investigation on thermomechanical cycles, including programming, cooling, unloading, and heating to trigger the 1WE, were carried out for Veriflex at 62°C (T < T g, below 5°C but near to T g) and also at 72°C (T > T g, above 5°C but near to T g) for strains of 140% and for a recovery time of 10 min. Accumulation of strain was estimated during the thermomechanical treatments for using strains of 140% at 62°C (T < T g) as well as at 72°C (T > T g). Recovery ratios for strains of 140% at 62°C (T < T g) as well as at 72°C (T > T g) were also estimated. It turns out that programming, cooling, unloading, and heating to trigger the 1WE causes an increase in irreversible strain and is associated with a corresponding decrease in the intensity of the 1WE in particular during the first thermomechanical cycles. Confocal laser scanning microscopic) study shows a very little wavy surface structure evolved during cycling up to strains of 140% at 72°C (T > T g). Infrared study features the chemical nature after cycling, processing, and programming of Veriflex.
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