Effect of nanoclay addition on the displacement-controlled flexural fatigue behavior of a polymer

Reinforcing polymers with nanoclay improves the stiffness and decreases the dissipative nature of polymer matrix. This article describes the effect of nanoclay addition on the flexural fatigue response of Polyamide6 (PA6). The emphasis was on temperature rise, temperature-induced stiffness drop, and flexural fatigue life. The fatigue performance has been investigated under displacement-controlled flexural loading conditions at room temperature. The samples were subjected to same displacement amplitude and same initial force amplitude (force amplitude in the first fatigue cycle) flexural fatigue conditions. Under the same displacement amplitude conditions, PA6NC samples exhibited marginally lesser percentage drop in the initial force amplitude (temperature-induced stiffness change) compared to PA6. Due to the addition of nanoclay, a marginal improvement in fatigue life (~64,000 cycles) was also observed under these conditions. Under the same initial force amplitude conditions, PA6NC samples exhibited significantly lesser percentage drop in its initial force compared to PA6 and retained the stiffness throughout the fatigue life. In addition to this, a significant improvement in fatigue life (>150,000 cycles) was observed. The performance improvement due to nanoclay addition can be attributed to enhanced modulus coupled with reduced dissipation factor (tan δ) and improved surface hardness. The fibrillated appearance of the PA6NC fracture surface suggests that the clay addition promotes toughening and influences the crack propagation characteristics of PA6.